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  • Oxford University Press  (15,748)
  • American Geophysical Union (AGU)
  • American Meteorological Society
  • Annual Reviews
  • 2020-2023  (167)
  • 2020-2022  (20,503)
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  • 1
    Publication Date: 2021-03-15
    Description: In a recent work we computed the relative frequencies with which strong shocks (4.0≤Mw〈5.0), widely felt by the population were followed in the same area by potentially destructive main shocks (Mw≥5.0) in Italy. Assuming the stationarity of the seismic release properties, such frequencies can be tentatively used to estimate the probabilities of potentially destructive shocks after the occurrence of future strong shocks. This allows us to set up an alarm-based forecasting hypothesis related to strong foreshocks occurrence. Such hypothesis is tested retrospectively on the data of a homogenized seismic catalogue of the Italian area against a purely random hypothesis that simply forecasts the target main shocks proportionally to the space-time fraction occupied by the alarms. We compute the latter fraction in two ways a) as the ratio between the average time covered by the alarms in each area and the total duration of the forecasting experiment (60 years) and b) as the same ratio but weighted by the past frequency of occurrence of earthquakes in each area. In both cases the overall retrospective performance of our forecasting algorithm is definitely better than the random case. Considering an alarm duration of three months, the algorithm retrospectively forecasts more than 70% of all shocks with Mw5.5 occurred in Italy from 1960 to 2019 with a total space-time fraction covered by the alarms of the order of 2%. Considering the same space-time coverage, the algorithm is also able to retrospectively forecasts more than 40% of the first main shocks with Mw5.5 of the seismic sequences occurred in the same time interval. Given the good reliability of our results, the forecasting algorithm is set and ready to be tested also prospectively, in parallel to other ongoing procedures operating on the Italian territory.
    Description: This paper benefitted from funding provided by the European Union within the ambit of the H2020 project RISE (No. 821115), which in particular fully financed the PhD grant of one of the authors (E.B.).
    Description: Published
    Description: 1192–1206
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: Earthquake interaction ; Statistical seismology ; forecasting, ; prediction ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
    Publication Date: 2020-10-16
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2019. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: The active tectonic processes in convergent margins confer a high degree of complexity to the crust. Determining the thermal structure is, therefore, key to better elucidate the nature of those processes. In order to reconstruct the thermal structure of the crust beneath the Italian peninsula, we combine the most recent and accurate shear-wave velocity model that is currently available with thermodynamic modelling, assuming a global average crustal composition with no lateral variations. Our model, presented in terms of Moho temperature and crustal thermal gradients, shows a very good agreement with the known thermal anomalies associated with the backarc spreading related to the Apennine subduction. Importantly, we envisage a new anomalous region of high Moho temperatures in NW Italy (T 〉 800 degrees C at 30 km), at the transition between the Alps and Apennine orogens. The lowest temperatures of our model, corresponding to geothermal gradients 〈 19 degrees C km(-1), are obtained in the still active but slow-convergent portion of the northern Apennine. Moho temperatures increase moving southwards along the Apennine chain, an observation that is coherent with the evidence of ceasing subduction and consequent rebalancing of the depressed isotherms along the slab. Our results suggest that a thermal structure in different tectonic settings can be inferred with acceptable uncertainties based on absolute seismic velocity models. In this sense, our approach can be extended to any other region.
    Description: Published
    Description: 239–247
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Publication Date: 2020-12-15
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2015. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: ectonic earthquake swarms challenge our understanding of earthquake processes since it is difficult to link observations to the underlying physical mechanisms and to assess the hazard they pose. Transient forcing is thought to initiate and drive the spatio-temporal release of energy during swarms. The nature of the transient forcing may vary across sequences and range from aseismic creeping or transient slip to diffusion of pore pressure pulses to fluid redistribution and migration within the seismogenic crust. Distinguishing between such forcing mechanisms may be critical to reduce epistemic uncertainties in the assessment of hazard due to seismic swarms, because it can provide information on the frequency–magnitude distribution of the earthquakes (often deviating from the assumed Gutenberg–Richter relation) and on the expected source parameters influencing the ground motion (for example the stress drop). Here we study the ongoing Pollino range (Southern Italy) seismic swarm, a long-lasting seismic sequence with more than five thousand events recorded and located since October 2010. The two largest shocks (magnitude M w = 4.2 and M w = 5.1) are among the largest earthquakes ever recorded in an area which represents a seismic gap in the Italian historical earthquake catalogue. We investigate the geometrical, mechanical and statistical characteristics of the largest earthquakes and of the entire swarm. We calculate the focal mechanisms of the M l 〉 3 events in the sequence and the transfer of Coulomb stress on nearby known faults and analyse the statistics of the earthquake catalogue. We find that only 25 per cent of the earthquakes in the sequence can be explained as aftershocks, and the remaining 75 per cent may be attributed to a transient forcing. The b-values change in time throughout the sequence, with low b-values correlated with the period of highest rate of activity and with the occurrence of the largest shock. In the light of recent studies on the palaeoseismic and historical activity in the Pollino area, we identify two scenarios consistent with the observations and our analysis: This and past seismic swarms may have been ‘passive’ features, with small fault patches failing on largely locked faults, or may have been accompanied by an ‘active’, largely aseismic, release of a large portion of the accumulated tectonic strain. Those scenarios have very different implications for the seismic hazard of the area.
    Description: Published
    Description: 1553–1567
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
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  • 4
    Publication Date: 2021-01-18
    Description: The horizontal to vertical spectral ratio (HVSR) of seismic noise is often used to investigate site effects, and it is usually assumed to be a stable feature of the site considered. Here we show that such an assumption is not always justified, and may lead to incorrect conclusions. The HVSR analysis was performed on ambient seismic noise recordings lasting from weeks to months at many sites in Calabria, Italy. Results show a variety of site effects, from the resonance of a shallow sedimentary layer to the polarized amplification of horizontal ground motion associated with topographic effects. We describe the results of seven sites whose HVSR is characterized by dual content: one that is persistent, and another appearing only occasionally. Two sites very near the coast of the Tyrrhenian sea and five sites in the Calabrian Arc mountains show the most remarkable results. The shape of the HVSR changes significantly at these sites when the amplitude of background noise increases in a broad frequency band during periods of bad weather. The occasional contribution to the HVSR consists of one or more peaks, depending on the site, that appear only when the amplitude of ambient noise is higher than usual. The seven sites where we observe the HVSR variability are all located in complex geological environments, on mountains, ridges or foothills. A variation of the HVSR correlated with the day–night cycle is also observed at some of these sites.
    Description: Published
    Description: 2162–2171
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2021-02-10
    Description: The 2007 caldera-forming eruption of Piton de la Fournaise (PdF) erupted the largest volume of magma (210 Mm3)recorded at this volcano in at least three centuries. Major and trace element and Sr^Nd isotope data for bulk-rocks, groundmasses and olivine phenocrysts have been combined with melt inclusion data (major, trace and volatile elements) to track magma evolution over the whole eruptive sequence. We show that each eruptive phase had a distinctive geochemical and petrological signature and that caldera collapse on 5 April was preceded by a marked shift in bulk magma composition and crystal content and size. Aphyric basalt erupted at the beginning of the sequence (February 2007) had relatively high Sr isotope ratio (87Sr/86Sr ¼ 0·70420^0·704180) and low Nd isotopic ratio(143Nd/144Nd ¼ 0·51285^0·51286). Olivine-basalts extruded on2^5 April just before caldera collapse are less enriched in radiogenic Sr (87Sr/86Sr ¼ 0·70412^0·70416), but characterized by the same Nd isotopic composition. This magma is interpreted as a new deep input, which pressurized the shallow PdF plumbing system and triggered the 2007 activity. Post-collapse oceanite lavas represent the main volume of magma extruded in 2007. Their bulk-rocks and groundmasses have 87Sr/86Sr (0·70418) intermediate between those of February and 5 April, and similar to those of the March 2007 and 2001^2006 lavas.We show that the Steady State Basalts (SSB) commonly erupted at PdF are hybrid melts, which result from multistep mixing between ‘alkaline’and ‘transitional’end-members. Our results lead us to propose a new model of the PdF plumbing system to reconcile the petrological, geochemical and geophysical observations: (1) the shallow portion (above sea level) of the PdF plumbing system hosts several small sills, in which magma experiences variable degrees of degassing, cooling and crystallization; (2) oceanite lavas result from the withdrawal of shallow harrisitic mushes stored at low pressures (548 MPa; 51800^2400 m depth) below both the volcano summit and its eastern flank; (3) water degassing plays a major role in fast magma crystallization at shallow depths. Multistep ascent and periodic extrusion of the shallow magmas is promoted by injections of deeper and hotter basaltic magma, containing up to 1·3 wt % H2O and 1630 ppm S. In 2007, the new deep input was the ultimate source of the large excess in sulfur degassing detected by satellites. Lateral draining and intrusion of magma below the eastern flank of the volcano are the cause of major volcano deformation, flank sliding and summit caldera collapse.
    Description: Published
    Description: 1287-1315
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Piton de la Fournaise ; plumbing system ; magma reservoir ; caldera collapse ; melt inclusions ; volatile budget ; isotope geochemistry ; basalt
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  • 6
    Publication Date: 2021-02-23
    Description: The preparation, initiation, and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocations, and postseismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear.
    Description: Published
    Description: 627–645
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
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  • 7
    Publication Date: 2021-03-24
    Description: The 2016–17 central Italy earthquake sequence began with the first mainshock near the town of Amatrice on August 24 (MW 6.0), and was followed by two subsequent large events near Visso on October 26 (MW 5.9) and Norcia on October 30 (MW 6.5), plus a cluster of 4 events with MW 〉 5.0 within few hours on January 18, 2017. The affected area had been monitored before the sequence started by the permanent Italian National Seismic Network (RSNC), and was enhanced during the sequence by temporary stations deployed by the National Institute of Geophysics and Volcanology and the British Geological Survey. By the middle of September, there was a dense network of 155 stations, with a mean separation in the epicentral area of 6–10 km, comparable to the most likely earthquake depth range in the region. This network configuration was kept stable for an entire year, producing 2.5 TB of continuous waveform recordings. Here we describe how this data was used to develop a large and comprehensive earthquake catalogue using the Complete Automatic Seismic Processor (CASP) procedure. This procedure detected more than 450,000 events in the year following the first mainshock, and determined their phase arrival times through an advanced picker engine (RSNI-Picker2), producing a set of about 7 million P- and 10 million S-wave arrival times. These were then used to locate the events using a non-linear location (NLL) algorithm, a 1D velocity model calibrated for the area, and station corrections and then to compute their local magnitudes (ML). The procedure was validated by comparison of the derived data for phase picks and earthquake parameters with a handpicked reference catalogue (hereinafter referred to as ‘RefCat’). The automated procedure takes less than 12 hours on an Intel Core-i7 workstation to analyse the primary waveform data and to detect and locate 3000 events on the most seismically active day of the sequence. This proves the concept that the CASP algorithm can provide effectively real-time data for input into daily operational earthquake forecasts, The results show that there have been significant improvements compared to RefCat obtained in the same period using manual phase picks. The number of detected and located events is higher (from 84,401 to 450,000), the magnitude of completeness is lower (from ML 1.4 to 0.6), and also the number of phase picks is greater with an average number of 72 picked arrival for a ML = 1.4 compared with 30 phases for RefCat using manual phase picking. These propagate into formal uncertainties of ± 0.9km in epicentral location and ± 1.5km in depth for the enhanced catalogue for the vast majority of the events. Together, these provide a significant improvement in the resolution of fine structures such as local planar structures and clusters, in particular the identification of shallow events occurring in parts of the crust previously thought to be inactive. The lower completeness magnitude provides a rich data set for development and testing of analysis techniques of seismic sequences evolution, including real-time, operational monitoring of b-value, time-dependent hazard evaluation and aftershock forecasting.
    Description: Published
    Description: 555–571
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: 04.06. Seismology
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  • 8
    Publication Date: 2021-05-12
    Description: erratum paper
    Description: Published
    Description: 1090-1092
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Theoretical seismology ; Seismic attenuation ; Seismic noise ; Surface waves ; Free oscillations ; Seismic interferometry ; 04.06. Seismology ; 04.01. Earth Interior
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  • 9
    Publication Date: 2021-05-12
    Description: This article has been accepted for publication inGeophysical Journal International ©The Author(s) 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: Determining the crustal structure of ocean island volcanoes is important to understand the formation and tectonic evolution of the oceanic lithosphere and tectonic swells in marine settings, and to assess seismic hazard in the islands. The Azores Archipelago is located near a triple junction system and is possibly under the influence of a mantle plume, being at the locus of a wide range of geodynamic processes. However, its crustal structure is still poorly constrained and debated due to the limited seismic coverage of the region and the peculiar linear geometry of the islands. To address these limitations, in this study we invert teleseismic Rayleigh wave ellipticity measurements for 1-D shear wave speed (VS) crustal models of the Azores Archipelago. Moreover, we test the reliability of these new models by using them in independent moment tensor inversions of local seismic data and demonstrate that our models improve the waveform fit compared to previous models. We find that data from the westernmost seismic stations used in this study require a shallower Moho depth (∼10 km) than data from stations in the eastern part of the archipelago (∼13–16 km). This apparent increase in the Moho depth with increasing distance from the mid-Atlantic ridge (MAR) is expected. However, the rate at which Moho deepens away from the MAR is greater than that predicted from a half-space cooling model, suggesting that local tectonic perturbations have modified crustal structure. The 1-D VS models obtained beneath the westernmost seismic stations also show higher wave speeds than for the easternmost stations, which correlates well with the ages of the islands except Santa Maria Island. We interpret the relatively low VS profile found beneath Santa Maria Island as resulting from underplating, which agrees with previous geological studies of the island. Compared to a recent receiver function study of the region, the shallow structure (top ∼2 km) in our models shows lower shear wave speed, which may have important implications for future hazard studies of the region. More generally, the new seismic crustal models we present in this study will be useful to better understand the tectonics, seismicity, moment tensors and strong ground motions in the region.
    Description: Published
    Description: 1232–1247
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
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  • 10
    Publication Date: 2021-05-12
    Description: The island of Pantelleria, located in the Sicily Channel Rift Zone (Italy), has been the site of violent peralkaline silicic magmatism alternating with minor effusive to low-intensity Strombolian erup- tions of basaltic composition. The basaltic rock suites exposed on the island were sampled to in- vestigate the plumbing system dynamics through the study of chemical stratigraphy and temporal records of olivine crystals. Our petrographic and geochemical observations, together with the com- positional variability of olivine, suggest different evolutionary histories for basaltic magmas erupted over two major periods divided by the 􏰃45 ka Green Tuff (GT) eruption. Core-to-rim com- positional traverses across olivine crystals document different types of zoning. We recognized oliv- ine zones affected by Fo oscillations at very fine scales in the inner cores, rims and/or in intermedi- ate portions of crystals and used them to reconstruct the residence and passage of crystals through different magmatic environments, with P–T–ƒO2 and compositional characteristics con- strained by thermodynamic modeling. The sequence of magmatic environments evidenced by oliv- ine zoning indicate that the pre-GT volcanic period was dominated by injection at shallow crustal levels (􏰃300–200 MPa) of primitive melts, initially moving from a deep storage zone at the crust- mantle boundary. Supply of this magma significantly decreased after the GT eruption, while the dy- namics of magma transfer within the upper portion of the plumbing system were greatly enhanced. The diffusive relaxation of olivine zoning provided the timing of storage and migration of a crystal through different environments. For magmas feeding the ancient (〉45 ka) basaltic activ- ity we retrieved transfer histories that are much longer (up to 􏰃3 years) if compared with those cal- culated for the post-GT basalts (1–9 months). The compositional and temporal dataset presented in this study supports the idea that the GT eruption and the subsequent collapse of the volcanic edi- fice could have caused major changes to the internal structural setting of Pantelleria, creating more favorable conditions for the migration of magmas in the upper portions of the plumbing system.
    Description: Published
    Description: egaa05
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
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  • 11
    Publication Date: 2021-05-12
    Description: Ischia, a volcanic island located 18 miles SW of Naples (Southern Italy), is a densely populated active caldera that last erupted in AD 1302. Melt inclusions in phenocrysts of the Vateliero and Cava Nocelle shoshonite^latite eruptive products (6th to 4th centuries BC) constrain the structure and nature of the Ischia deep magmatic feeding system.Their geochemical characteristics make Ischia a natural borehole for probing the physico-chemical conditions of magma generation in mantle contaminated by slab-derived fluids or melts, largely dominated by CO2.Volatile concentrations in olivine-hosted melt inclusions require gas^melt equilibria at between 3 and 18 km depth. In agreement with what has already been demonstrated at the other neighboring Neapolitan volcanoes (Procida, Campi Flegrei caldera and Somma^Vesuvius volcanic complex), a major crystallization depth at 8^10 km has been identified.The analyzed melt inclusions provide clear evidence for CO2-dominated gas fluxing and consequent dehydration of magma batches stagnating at crustal discontinuities. Gas fluxing is further supported by selective enrichment in K owing to fluid-transfer during magma differentiation.This takes place under oxidized conditions (Fe3þ /Fe 0·3) that can be fixed by an equimolar proportion of divalent and trivalent iron in the melt if post-entrapment crystallization of the host olivine is discarded.The melt inclusion data, together with data from the literature for other Neapolitan volcanoes, show that magmatism and volcanism in the Neapolitan area, despite differences in composition and eruption dynamics, are closely linked to supercritical CO2-rich fluids. These fluids are produced by devolatilization of subducting terrigenous^pelagic metasediments and infiltrate the overlying mantle wedge, generate magmas and control their ascent up to eruption. Geochemical characteristics of Ischia and the other Neapolitan volcanoes reveal that the extent of fluid or melt contamination of the pre-subduction asthenospheric mantle wedge was similar among these volcanoes. However, differences in the isotopic compositions of the erupted magmas (more enriched in radiogenic Sr at Ischia, Campi Flegrei and Somma^Vesuvius with respect to Procida) and the amount of H2O in the plumbing system of these volcanoes (almost double at Ischia, Campi Flegrei and Somma^Vesuvius than at Procida) reflect the different flow-rates of deep slab-derived fluids or melts through the mantle wedge, which, in turn, control the amount of generated magma.The high bulk permeability of the lithosphere below Ischia, Campi Flegrei and Somma^Vesuvius, determined by the occurrence of intersecting NW^SE and NE^SW regional fault systems, favours fluid ascent and accumulation at crustal levels, with consequent larger magma production and storage than at Procida, located along the NE^SW system.
    Description: Published
    Description: 951-984
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: CO2-fluxing ; melt inclusions ; redox state ; trachybasalts
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 12
    Publication Date: 2021-06-21
    Description: Sulphur behaviour and variations in redox conditions during magma differentiation and degassing in the Mt Etna (Italy) volcanic system have been explored by integrating the study of olivine-hosted melt inclusions (MIs) with an experimental survey of sulphur solubility in hydrous basaltic magmas. Sulphur solubility experiments were performed at conditions relevant to the Etnean plumbing system (1200 C, 200MPa and oxygen fugacity between NNOþ0 2 and NNOþ1 7, with NNO being the nickel–nickel oxide buffer), and their results confirm the important control of oxygen fugacity (fO2) on S abundance in mafic magmas and on S partitioning between fluid and melt phases (DSfluid/melt). The observed DSfluid/melt value increases from 5164 to 14666 when fO2 decreases from NNOþ1 760 5 to NNOþ0 3. Based on the calculated DSfluid/melt and a careful selection of previously published data, an empirical model is proposed for basaltic magmas to predict the variation of DSfluid/melt values with variations in P (25–300 MPa), T (1030–1200 C) and fO2 (between NNO– 0 8 and NNOþ2 4). Olivine-hosted melt inclusions (Fo89-91) from tephra of the prehistoric (4 ka BP) sub-plinian picritic eruption, named FS (‘Fall Stratified’), have been investigated for their major element compositions, volatile contents and iron speciation (expressed as Fe3þ/PFe ratio). These primitive MIs present S content from 235677 to 34456168 ppm, and oxygen fugacity values, estimated from Fe3þ/PFe ratios, range from NNOþ0 760 2 to NNOþ1 660 2. Iron speciation has also been investigated in more evolved and volatile-poorer Etnean MIs. The only primitive melt inclusion from the Mt Spagnolo eruption (4–15 ka BP) presents a S content of 1515649ppm and an estimated fO2 of NNOþ1 460 1. The more evolved MIs (from 2002–2003, 2006, 2008–2009 and 2013 eruptions) have S content lower than 500 ppm, and their Fe3þ/RFe ratios result in fO2 between NNO– 0 960 1 and NNOþ0 460 1. Redox conditions and S behaviour in Etnean magmas during degassing and fractional crystallization were modelled coupling MELTS code with our empirical DSfluid/melt model. Starting from an FS-type magma composition and upon decrease of T and P, fractional crystallization of olivine, clinopyroxene, spinel and plagioclase causes a significant fO2 decrease. The fO2 reduction, in turn, causes a decrease in sulphur solubility and an increase in DSfluid/melt, promoting S exsolution during magma ascent, which further enhances the reduction of fO2. For the evolved MIs of 2002–2013 eruptions, magma differentiation may therefore have played a crucial role in decreasing redox conditions and favouring efficient S degassing. Differently, during the unusual FS eruption, only limited melt evolution is observed and S exsolution seems to have been triggered by a major pressure decrease accompanied by H2O and CO2 exsolution during fast magmatic ascent.
    Description: Published
    Description: egaa095
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: melt inclusions ; sulphur solubility experiments ; XANES ; Mt. Etna ; 04.08. Volcanology
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  • 13
    Publication Date: 2020-10-16
    Description: The behaviour of tsunami waves at any location depends on the local morphology of the coasts, the encountered bathymetric features, and the characteristics of the source. However, the importance of accurately modelling the geometric properties of the causative fault for simulations of seismically induced tsunamis is rarely addressed. In this work, we analyse the effects of using two different geometric models of the subduction interface of the Calabrian Arc (southern Italy, Ionian Sea) onto the simulated tsunamis: a detailed 3-D subduction interface obtained from the interpretation of a dense network of seismic reflection profiles, and a planar interface that roughly approximates the 3-D one. These models can be thought of as representing two end-members of the level of knowledge of fault geometry. We define three hypothetical earthquake ruptures of different magnitudes (Mw 7.5, 8.0, 8.5) on each geometry. The resulting tsunami impact is evaluated at the 50-m isobath in front of coastlines of the central and eastern Mediterranean. Our results show that the source geometry imprint is evident on the tsunami waveforms, as recorded at various distances and positions relative to the source. The absolute differences in maximum and minimum wave amplitudes locally exceed one metre, and the relative differences remain systematically above 20 per cent with peaks over 40 per cent. We also observe that tsunami energy directivity and focusing due to bathymetric waveguides take different paths depending on which fault is used. Although the differences increase with increasing earthquake magnitude, there is no simple rule to anticipate the different effects produced by these end-member models of the earthquake source. Our findings suggest that oversimplified source models may hinder our fundamental understanding of the tsunami impact and great care should be adopted when making simplistic assumptions regarding the appropriateness of the planar fault approximation in tsunami studies. We also remark that the geological and geophysical 3-D fault characterization remains a crucial and unavoidable step in tsunami hazard analyses.
    Description: Published
    Description: 1805–1819
    Description: 3T. Sorgente sismica
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
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  • 14
    Publication Date: 2021-04-14
    Description: The scaling of earthquake parameters with seismic moment and its interpretation in terms of self- similarity is still debated in the literature. We address this question by examining a worldwide compilation of corner frequency-based and elastic rebound theory (ERT)-based fault slip, area and stress drop values for earthquakes ranging in magnitude from -0.7 to 7.8. We find that corner frequency estimates of slip (and stress drop) scale differently than those inferred from the ERT approach, where the latter deviates from the generally accepted constant stress drop behavior of so- called self-similar scaling models. We also find that average slips from finite-source models are consistent with corner frequency scaling, whereas peak slip values are more consistent with the ERT scaling. The different scaling of corner frequency- and ERT-based estimates of slip and stress drop with earthquake size is interpreted in terms of heterogeneity of the rupture process. ERT-based estimates of stress drop decrease with seismic moment suggesting a self-affine behavior. Despite the inferred heterogeneity at all scales, we do not observe a clear effect on the Brune stress drop scaling with earthquake size.
    Description: Published
    Description: 1771–1781
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: Earthquake dynamics ; Earthquake source observations ; Dynamics and mechanics of faulting ; 04.06. Seismology
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  • 15
    Publication Date: 2020-11-11
    Description: This article has been accepted for publication in Geophysical Journal International ©: 2021 The Author(s) 2020. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: In this short paper we show how to use the classical maximum likelihood estimation procedure for the b-value of the Gutenberg–Richter law for catalogues with different levels of completeness. With a simple correction, that is subtracting the relative completeness level to each magnitude, it becomes possible to use the classical approach. Moreover, this correction allows to adopt the testing procedures, initially made for catalogues with a single level of completeness, for catalogues with different levels of completeness too.
    Description: Published
    Description: 337–339
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
    Publication Date: 2020-12-21
    Description: This article has been accepted for publication in Geophysical Journal International. Published by Oxford University Press on behalf of the Royal Astronomical Society.
    Description: The classical procedure of the Probabilistic Seismic Hazard Analysis (PSHA) requires a Poissonian distribution of earthquakes. Seismic catalogs follow a Poisson distribution just after the application of a declustering algorithm that leaves only one earthquake for each seismic sequence (usually the stronger, i.e. the main shock). Removing earthquakes from the seismic catalogs leads to underestimation of the annual rates of the events and consequently associate with low seismic hazard as indicated by several studies. In this study, we aim investigating the performance of two declustering methods on the Italian instrumental catalog and the impact of declustering on estimation of the b-value and on the seismic hazard analysis. To this end, first the spatial variation in the seismicity rate was estimated from the declustered catalogs using the adaptive smoothed seismicity approach, considering small earthquakes (Mw≥3.0). We then corrected the seismicity rates using new approach that allows for counting all events in the complete seismic catalog by simply changing the magnitude frequency distribution. The impact of declustering on seismic hazard analysis is illustrated using PSHA maps in terms of peak ground acceleration (PGA) and spectral acceleration (SA) in 2 s, with 10% and 2% probability of exceedance in 50 years, for Italy. We observed that the hazard calculated from the declustered catalogs was always lower than the hazard computed using the complete catalog. These results are in agreement with previous results obtained in different parts of the world.
    Description: Published
    Description: 1174–1187
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
    Publication Date: 2021-05-12
    Description: Producing probabilistic subseasonal forecasts of extreme events up to six weeks in advance is crucial for many economic sectors. In agribusiness, this time scale is particularly critical because it allows for mitigation strategies to be adopted for counteracting weather hazards and taking advantage of opportunities. For example, spring frosts are detrimental for many nut trees, resulting in dramatic losses at harvest time. To explore subseasonal forecast quality in boreal spring, identified as one of the most sensitive times of the year by agribusiness end users, we build a multisystem ensemble using four models involved in the Subseasonal to Seasonal Prediction project (S2S). Two-meter temperature forecasts are used to analyze cold spell predictions in the coastal Black Sea region, an area that is a global leader in the production of hazelnuts. When analyzed at the global scale, the multisystem ensemble probabilistic forecasts for near-surface temperature are better than climatological values for several regions, especially the tropics, even many weeks in advance; however, in the coastal Black Sea, skill is low after the second forecast week. When cold spells are predicted instead of near-surface temperatures, skill improves for the region, and the forecasts prove to contain potentially useful information to stakeholders willing to put mitigation plans into effect. Using a cost–loss model approach for the first time in this context, we show that there is added value of having such a forecast system instead of a business-as-usual strategy, not only for predictions released 1–2 weeks ahead of the extreme event, but also at longer lead times.
    Description: Published
    Description: 237–254
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 18
    Publication Date: 2021-05-12
    Description: We have constructed a 3-D shear wave velocity (Vs) model for the crust and uppermost mantle beneath the Middle East using Rayleigh wave records obtained from ambient-noise cross-correlations and regional earthquakes. We combined one decade of data collected from 852 permanent and temporary broad-band stations in the region to calculate group-velocity dispersion curves. A compilation of 〉54 000 ray paths provides reliable group-velocity measurements for periods between 2 and 150 s. Path-averaged group velocities calculated at different periods were inverted for 2-D group-velocity maps. To overcome the problem of heterogeneous ray coverage, we used an adaptive grid parametrization for the group-velocity tomographic inversion. We then sample the period-dependent group-velocity field at each cell of a predefined grid to generate 1-D group-velocity dispersion curves, which are subsequently inverted for 1-D Vs models beneath each cell and combined to approximate the 3-D Vs structure of the area. The Vs model shows low velocities at shallow depths (5–10 km) beneath the Mesopotamian foredeep, South Caspian Basin, eastern Mediterranean and the Black Sea, in coincidence with deep sedimentary basins. Shallow high-velocity anomalies are observed in regions such as the Arabian Shield, Anatolian Plateau and Central Iran, which are dominated by widespread magmatic exposures. In the 10–20 km depth range, we find evidence for a band of high velocities (〉4.0 km s–1) along the southern Red Sea and Arabian Shield, indicating the presence of upper mantle rocks. Our 3-D velocity model exhibits high velocities in the depth range of 30–50 km beneath western Arabia, eastern Mediterranean, Central Iranian Block, South Caspian Basin and the Black Sea, possibly indicating a relatively thin crust. In contrast, the Zagros mountain range, the Sanandaj-Sirjan metamorphic zone in western central Iran, the easternmost Anatolian plateau and Lesser Caucasus are characterized by low velocities at these depths. Some of these anomalies may be related to thick crustal roots that support the high topography of these regions. In the upper mantle depth range, high-velocity anomalies are obtained beneath the Arabian Platform, southern Zagros, Persian Gulf and the eastern Mediterranean, in contrast to low velocities beneath the Red Sea, Arabian Shield, Afar depression, eastern Turkey and Lut Block in eastern Iran. Our Vs model may be used as a new reference crustal model for the Middle East in a broad range of future studies.
    Description: Published
    Description: 1349-1365
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: 04.01. Earth Interior ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 19
    Publication Date: 2020-07-13
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 20
    Publication Date: 2021-07-23
    Description: Marine aquaculture holds great promise for meeting increasing demand for healthy protein that is sustainably produced, but reaching necessary production levels will be challenging. The ecosystem approach to aquaculture is a framework for sustainable aquaculture development that prioritizes multiple-stakeholder participation and spatial planning. These types of approaches have been increasingly used to help guide sustainable, persistent, and equitable aquaculture planning, but most countries have difficulties in setting or meeting longer-term development goals. Scenario analysis (SA) for future planning uses similar approaches and can complement holistic methods, such as the ecosystem approach to aquaculture framework, by providing a temporal analogue to the spatially robust design. Here we define the SA approach to planning in aquaculture, outline how SA can benefit aquaculture planning, and review how this tool is already being used. We track the use of planning tools in the 20 International Council for the Exploration of the Sea member nations, with particular attention given to Norway’s development goals to 2050. We conclude that employing a combination of an ecosystem framework with scenario analyses may help identify the scale of development aquaculture goals over time, aid in evaluating the feasibility of the desired outcomes, and highlight potential social-ecological conflicts and trade-offs that may otherwise be overlooked.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 21
    Publication Date: 2020-06-17
    Description: Petrological and geochemical (major element, trace element, Sr–Nd isotope) data for recent (〈5 kyr old) basalts that sporadically erupt on the western flank of Piton de la Fournaise (PdF), one of the most active volcanoes on Earth, allow the tracking of magma transfer and evolution from mantle to crustal depths. In the western peripheral area of PdF we document the broadly synchronous eruptions of (1) primitive olivine and olivine–clinopyroxene transitional basalts with tholeiitic affinity 30 that are closely associated in space with (2) transitional olivine basalts with alkaline affinity, and (3) hybrid lavas, intermediate between the ‘alkaline’ and the ‘tholeiitic’ end-members. The composition of the latter overlaps with that of the lavas frequently erupted from the conduit system feeding the main summit cone. AlphaMELTS modelling, and fluid inclusion and clinopyroxene barometry, constrain the conditions of magma storage at 10–30 km, and the ascent of magma from the upper 35 mantle to the shallow crustal plumbing system. Variable degrees of mantle melting, together with minor source heterogeneity and contamination with cumulate-derived partial melts, contribute to the diversity of PdF magmas. However, all these processes do not represent the dominant factors that produce the large variability we found in major element composition. Indeed, the composition of basalts erupted from PdF peripheral centers is strongly controlled by polybaric olivine–clinopyr- 40 oxene fractionation at pressures higher than 3 kbar. Crystal textures and geochemical modelling suggest that fast magma ascent is critical to prevent clinopyroxene dissolution. Conversely, longlasting magma stagnation promotes pyroxene resorption and magma differentiation. ‘Central’ eruptions occurring close to the PdF summit cone emit variably more evolved melts, which result from olivine–clinopyroxene–plagioclase differentiation at intermediate–shallow pressure (〈3 kbar and in most cases 〈1 kbar). Deep and extensive magma mixing before injection into the crustal magma conduit system, located below the summit region, results in the apparent homogeneity of basalts erupted from the central area. As regards ‘peripheral’ eruptions, deep-seated stagnation of basaltic melts and differentiation at the mantle–crust transition zone (c. 4 kbar) produces a range of 5 magma compositions. We demonstrate that rapid magma ascent from deep-seated reservoirs can bypass the central plumbing system. The eruptions of these magmas both in the central area and on the densely populated flanks have major consequences in terms of volcanic hazard at PdF.
    Description: Published
    Description: 1717–1752
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: transitional basalts ; clinopyroxene crystallization and resorption ; mantle–crust underplating
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 22
    Publication Date: 2022-03-02
    Description: Crystalline rocks can produce dangerous radiation levels on the basis of their content in radioisotopes. Here, we report radiological data from 10 metamorphic and igneous rock samples collected from the crystalline basement of the Peloritani Mountains (southern Italy). In order to evaluate the radiological properties of these rocks, the gamma radiation and the radon emanation have been measured. Moreover, since some of these rocks are employed as building materials, we assess the potential hazard for population connected to their use. Gamma spectroscopy was used to measure the 226Ra, 232Th and 40K activity concentration, whereas the radon emanation was investigated by using a RAD 7 detector. The results show 226Ra, 232Th and 40K activity concentration values ranging from (17 ± 4) to (56 ± 8) Bq kg-1, (14 ± 3) to (77 ± 14) Bq kg-1 and (167 ± 84) to (1760 ± 242) Bq kg-1, respectively. Values of the annual effective dose equivalent outdoor range from 0.035 to 0.152 mSv y-1, whereas the gamma index is in the range of 0.22-0.98. The 222Rn emanation coefficient and the 222Rn surface exhalation rate vary from (0.63 ± 0.3) to (8.27 ± 1.6)% and from (0.12 ± 0.03) to (2.75 ± 0.17) Bq m-2 h-1, respectively. The indoor radon derived from the building use of these rocks induces an approximate contribution to the annual effective dose ranging from 8 to 176 μSv y-1. All the obtained results suggest that the crystalline rocks from the Peloritani Mountains are not harmful for the residential population, even though they induce annual effective doses due to terrestrial gamma radiation above the worldwide average values. Moreover, their use as building materials does not produce significant health hazards connected to the indoor radon exposure.
    Description: Published
    Description: 452–464
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 23
    Publication Date: 2022-03-07
    Description: The Pollino range is a region of slow deformation where earthquakes generally nucleate on low-angle normal faults. Recent studies have mapped fault structures and identified fluid related dynamics responsible for historical and recent seismicity in the area. Here, we apply the coda-normalization method at multiple frequencies and scales to image the 3-D P-wave attenuation (QP) properties of its slowly deforming fault network. The wide-scale average attenuation properties of the Pollino range are typical for a stable continental block, with a dependence of QP on frequency of Q−1 P = (0.0011   0.0008) f (0.36 0.32). Using only waveforms comprised in the area of seismic swarms, the dependence of attenuation on frequency increases [Q−1 P = (0.0373   0.0011) f (−0.59 0.01)], as expected when targeting seismically active faults. A shallow very-low-attenuation anomaly (max depth of 4–5 km) caps the seismicity recorded within the western cluster 1 of the Pollino seismic sequence (2012, maximum magnitude Mw = 5.1). High-attenuation volumes below this anomaly are likely related to fluid storage and comprise the western and northern portions of cluster 1 and the Mercure basin. These anomalies are constrained to the NW by a sharp low-attenuation interface, corresponding to the transition towards the eastern unit of the Apennine Platform under the Lauria mountains. The low-seismicity volume between cluster 1 and cluster 2 (maximum magnitude Mw = 4.3, east of the primary) shows diffuse low-to-average attenuation features. There is no clear indication of fluid-filled pathways between the two clusters resolvable at our resolution. In this volume, the attenuation values are anyway lower than in recognized low-attenuation blocks, like the Lauria Mountain and Pollino Range. As the volume develops in a region marked at surface by small-scale cross-faulting, it suggests no actual barrier between clusters, more likely a system of small locked fault patches that can break in the future. Our model loses resolution at depth, but it can still resolve a 5-to-15-km-deep high-attenuation anomaly that underlies the Castrovillari basin. This anomaly is an ideal deep source for the SE-to-NW migration of historical seismicity. Our novel deep structural maps support the hypothesis that the Pollino sequence has been caused by a mechanism of deep and lateral fluid-induced migration.
    Description: Natural Environment Research Council (NERC) Centre for Doctoral Training (CDT) in Oil and Gas. University of Aberdeen.
    Description: Published
    Description: 536–547
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: body waves ; seismic attenuation ; seismic tomography ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 24
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Carroll, E. L., Ott, P. H., McMillan, L. F., Galletti Vernazzani, B., Neveceralova, P., Vermeulen, E., Gaggiotti, O. E., Andriolo, A., Baker, C. S., Bamford, C., Best, P., Cabrera, E., Calderan, S., Chirife, A., Fewster, R. M., Flores, P. A. C., Frasier, T., Freitas, T. R. O., Groch, K., Hulva, P., Kennedy, A., Leaper, R., Leslie, M. S., Moore, M., Oliveira, L., Seger, J., Stepien, E. N., Valenzuela, L. O., Zerbini, A., & Jackson, J. A. Genetic diversity and connectivity of southern right whales (Eubalaena australis) found in the Brazil and Chile-Peru wintering grounds and the South Georgia (Islas Georgias del Sur) feeding ground. Journal of Heredity, 111(3), (2020): 263-276, doi:10.1093/jhered/esaa010.
    Description: As species recover from exploitation, continued assessments of connectivity and population structure are warranted to provide information for conservation and management. This is particularly true in species with high dispersal capacity, such as migratory whales, where patterns of connectivity could change rapidly. Here we build on a previous long-term, large-scale collaboration on southern right whales (Eubalaena australis) to combine new (nnew) and published (npub) mitochondrial (mtDNA) and microsatellite genetic data from all major wintering grounds and, uniquely, the South Georgia (Islas Georgias del Sur: SG) feeding grounds. Specifically, we include data from Argentina (npub mtDNA/microsatellite = 208/46), Brazil (nnew mtDNA/microsatellite = 50/50), South Africa (nnew mtDNA/microsatellite = 66/77, npub mtDNA/microsatellite = 350/47), Chile–Peru (nnew mtDNA/microsatellite = 1/1), the Indo-Pacific (npub mtDNA/microsatellite = 769/126), and SG (npub mtDNA/microsatellite = 8/0, nnew mtDNA/microsatellite = 3/11) to investigate the position of previously unstudied habitats in the migratory network: Brazil, SG, and Chile–Peru. These new genetic data show connectivity between Brazil and Argentina, exemplified by weak genetic differentiation and the movement of 1 genetically identified individual between the South American grounds. The single sample from Chile–Peru had an mtDNA haplotype previously only observed in the Indo-Pacific and had a nuclear genotype that appeared admixed between the Indo-Pacific and South Atlantic, based on genetic clustering and assignment algorithms. The SG samples were clearly South Atlantic and were more similar to the South American than the South African wintering grounds. This study highlights how international collaborations are critical to provide context for emerging or recovering regions, like the SG feeding ground, as well as those that remain critically endangered, such as Chile–Peru.
    Description: This work was supported by the EU BEST 2.0 medium grant 1594 and UK DARWIN PLUS grant 057 and additional funding from the World Wildlife Fund GB107301. The collection of the Chile–Peru sample was supported by the Global Greengrants Fund and the Pacific Whale Foundation. The collection of the Brazilian samples was supported through grants by the Brazilian National Research Council to Paulo H. Ott (CNPq proc. n° 144064/98-7) and Paulo A.C. Flores (CNPq proc. n° 146609/1999-9) and with support from the World Wildlife Fund (WWF-Brazil). The collection of the South African samples was supported by the Global Greengrants Fund, the Pacific Whale Foundation and Charles University Grant Agency (1140217). E.L.C. was partially supported by a Rutherford Discovery Fellowship from the Royal Society of New Zealand. This study forms part of the Ecosystems component of the British Antarctic Survey Polar Sciences for Planet Earth Programme, funded by the Natural Environment Research Council.
    Keywords: population structure ; connectivity ; migration ; gene flow
    Repository Name: Woods Hole Open Access Server
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  • 25
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(9), (2020): 3845-3862, doi:10.1175/JCLI-D-19-0215.1.
    Description: The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.
    Description: The authors gratefully acknowledge support from the Physical Oceanography Program of the U.S. National Science Foundation (Awards OCE-1756143 and OCE-1537136) and the Climate Program Office of the National Oceanic and Atmospheric Administration (Award NA15OAR4310088). Gratitude is extended to Claus Böning and Arne Biastoch who shared ORCA025 output. S. Zou thanks F. Li, M. Buckley, and L. Li for helpful discussions. We also thank three anonymous reviewers for helpful suggestions.
    Keywords: Deep convection ; Ocean circulation ; Thermocline circulation
    Repository Name: Woods Hole Open Access Server
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  • 26
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Hahn, L. C., Storelvmo, T., Hofer, S., Parfitt, R., & Ummenhofer, C. C. Importance of Orography for Greenland cloud and melt response to atmospheric blocking. Journal of Climate, 33(10), (2020): 4187-4206, doi:10.1175/JCLI-D-19-0527.1.
    Description: More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet.
    Description: This research was supported by the Woods Hole Oceanographic Institution Summer Student Fellow program, by the U.S. National Science Foundation under AGS-1355339 to C.C.U., and by the European Research Council through Grant 758005.
    Keywords: Ice sheets ; Blocking ; Cloud cover ; Topographic effects ; Climate change ; Climate variability
    Repository Name: Woods Hole Open Access Server
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  • 27
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    Unknown
    Oxford University Press
    In:  EPIC3The Natural History of the Crustacea, Vol. 6: Reproductive Biology, New York, U.S.A., Oxford University Press, 30 p., pp. 277-306, ISBN: 9780190688554
    Publication Date: 2021-02-24
    Description: Due to an exceptional variety of habitats, body plans, and lifestyles, crustaceans exhibit a wide array of mating systems. Some groups engage in simple, pure- search polygamous systems in which males usually search for receptive females. In other groups, males defend valuable resources to attract and/ or guard females to ensure paternity. Some species have developed highly complex systems of harem defense polygyny and monogamy, even cases of sub- and eusociality are reported. The expression of mating systems does not seem to be uniformly correlated to taxonomic affiliation, but is rather diverse within certain groups, suggesting that the evolution of mating systems is largely facilitated by the lifestyle of the species. Despite the broad range of mating systems in crustaceans, and although some groups have been studied comparably well, there remains a lack of knowledge about the behavioral and sexual biology of many species. In the light of the high diversity of lifestyles, mating systems, and habitats of certain groups, crustacean species would be ideal models to unravel the evolution of reproductive strategies and social behaviors.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 28
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    Unknown
    American Meteorological Society
    Publication Date: 2020-03-16
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(4), (2020): 1535-1545, doi:10.1175/JCLI-D-19-0547.1.
    Description: In a transient warming scenario, the North Atlantic is influenced by a complex pattern of surface buoyancy flux changes that ultimately weaken the Atlantic meridional overturning circulation (AMOC). Here we study the AMOC response in the CMIP5 experiment, using the near-geostrophic balance of the AMOC on interannual time scales to identify the role of temperature and salinity changes in altering the circulation. The thermal wind relationship is used to quantify changes in the zonal density gradients that control the strength of the flow. At 40°N, where the overturning cell is at its strongest, weakening of the AMOC is largely driven by warming between 1000- and 2000-m depth along the western margin. Despite significant subpolar surface freshening, salinity changes are small in the deep branch of the circulation. This is likely due to the influence of anomalously salty water in the subpolar intermediate layers, which is carried northward from the subtropics in the upper limb of the AMOC. In the upper 1000 m at 40°N, salty anomalies due to increased evaporation largely cancel the buoyancy increase due to warming. Therefore, in CMIP5, temperature dynamics are responsible for AMOC weakening, while freshwater forcing instead acts to strengthen the circulation in the net. These results indicate that past modeling studies of AMOC weakening, which rely on freshwater hosing in the subpolar gyre, may not be directly applicable to a more complex warming scenario.
    Description: We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups (listed in Table 1 of this paper) for producing and making available their model output. We also thank John Marshall for helpful discussions on the driving mechanisms of the AMOC, and three anonymous reviewers whose comments greatly improved the manuscript. This work was supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program Award 80NSSC17K0372, and by National Science Foundation Award OCE-1433132.
    Description: 2020-07-20
    Keywords: North Atlantic Ocean ; Thermohaline circulation ; Water masses/storage ; Climate change ; Climate prediction ; Climate models
    Repository Name: Woods Hole Open Access Server
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  • 29
    Publication Date: 2022-03-16
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2021. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: In a recent study (Jozinovi\'c et al, 2020) we showed that convolutional neural networks (CNNs) applied to network seismic traces can be used for rapid prediction of earthquake peak ground motion intensity measures (IMs) at distant stations using only recordings from stations near the epicenter. The predictions are made without any previous knowledge concerning the earthquake location and magnitude. This approach differs from the standard procedure adopted by earthquake early warning systems (EEWSs) that rely on location and magnitude information. In the previous study, we used 10 s, raw, multistation waveforms for the 2016 earthquake sequence in central Italy for 915 events (CI dataset). The CI dataset has a large number of spatially concentrated earthquakes and a dense station network. In this work, we applied the CNN model to an area around the VIRGO gravitational waves observatory sited near Pisa, Italy. In our initial application of the technique, we used a dataset consisting of 266 earthquakes recorded by 39 stations. We found that the CNN model trained using this smaller dataset performed worse compared to the results presented in the original study by Jozinovi\'c et al. (2020). To counter the lack of data, we adopted transfer learning (TL) using two approaches: first, by using a pre-trained model built on the CI dataset and, next, by using a pre-trained model built on a different (seismological) problem that has a larger dataset available for training. We show that the use of TL improves the results in terms of outliers, bias, and variability of the residuals between predicted and true IMs values. We also demonstrate that adding knowledge of station positions as an additional layer in the neural network improves the results. The possible use for EEW is demonstrated by the times for the warnings that would be received at the station PII.
    Description: RISE (Union's Horizon 2020 research and innovation programme, grant agreement No.821115)
    Description: Published
    Description: 704–718
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Keywords: Physics - Geophysics; Physics - Geophysics ; machine learning ; ground motion prediction ; seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 30
    Publication Date: 2022-03-01
    Description: To examine the atmospheric responses to Arctic sea ice variability in the Northern Hemisphere cold season (from October to the following March), this study uses a coordinated set of large-ensemble experiments of nine atmospheric general circulation models (AGCMs) forced with observed daily varying sea ice, sea surface temperature, and radiative forcings prescribed during the 1979–2014 period, together with a parallel set of experiments where Arctic sea ice is substituted by its climatology. The simulations of the former set reproduce the near-surface temperature trends in reanalysis data, with similar amplitude, and their multimodel ensemble mean (MMEM) shows decreasing sea level pressure over much of the polar cap and Eurasia in boreal autumn. The MMEM difference between the two experiments allows isolating the effects of Arctic sea ice loss, which explain a large portion of the Arctic warming trends in the lower troposphere and drive a small but statistically significant weakening of the wintertime Arctic Oscillation. The observed interannual covariability between sea ice extent in the Barents–Kara Seas and lagged atmospheric circulation is distinguished from the effects of confounding factors based on multiple regression, and quantitatively compared to the covariability in MMEMs. The interannual sea ice decline followed by a negative North Atlantic Oscillation–like anomaly found in observations is also seen in the MMEM differences, with consistent spatial structure but much smaller amplitude. This result suggests that the sea ice impacts on trends and interannual atmospheric variability simulated by AGCMs could be underestimated, but caution is needed because internal atmospheric variability may have affected the observed relationship.
    Description: Published
    Description: 8419–8443
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Arctic ; Sea ice ; Atmospheric circulation ; Climate models ; 01.01. Atmosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 31
    Publication Date: 2021-12-24
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2021. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: Ambient-noise records from the AlpArray network are used to measure Rayleigh wave phase velocities between more than 150,000 station pairs. From these, azimuthally anisotropic phase-velocity maps are obtained by applying the Eikonal tomography method. Several synthetic tests are shown to study the bias in the Ψ2 anisotropy. There are two main groups of bias, the first one caused by interference between refracted/reflected waves and the appearance of secondary wavefronts that affect the phase travel-time measurements. This bias can be reduced if the amplitude field can be estimated correctly. Another source of error is related to the incomplete reconstruction of the travel-time field that is only sparsely sampled due to the receiver locations. Both types of bias scale with the magnitude of the velocity heterogeneities. Most affected by the spurious Ψ2 anisotropy are areas inside and at the border of low-velocity zones. In the isotropic velocity distribution, most of the bias cancels out if the azimuthal coverage is good. Despite the lack of resolution in many parts of the surveyed area, we identify a number of anisotropic structures that are robust: in the central Alps, we find a layered anisotropic structure, arc-parallel at midcrustal depths and arc-perpendicular in the lower crust. In contrast, in the eastern Alps, the pattern is more consistently E-W oriented which we relate to the eastward extrusion. The northern Alpine forleand exhibits a preferential anisotropic orientation that is similar to SKS observations in the lowermost crust and uppermost mantle.
    Description: German Science Foundation (SPP-2017, Project Ha 2403/21-1); Swiss National Science Foundation SINERGIA Project CRSII2-154434/1 (Swiss-AlpArray); Progetto Pianeta Dinamico, finanziamento MUR-INGV, Task S2 – 2021
    Description: Published
    Description: 151–170
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Seismic anisotropy ; Seismic interferometry ; Seismic tomography ; Wave propagation ; Continental tectonics: compressional ; 04.01. Earth Interior ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 32
    Publication Date: 2021-12-15
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2022. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: To understand the seismotectonics and the seismic hazard of the study sector of the Northern Apennines (Italy), one of the most important earthquakes of magnitude Mw = 6.5 which struck the Lunigiana and Garfagnana areas (Tuscany) on 7 September 1920 should be studied. Given the early instrumental epoch of the event, neither geometric and kinematic information on the fault-source nor its fault-plane solution were available. Both areas were candidates for hosting the source fault and there was uncertainty between a normal fault with Apenninic direction or an anti-Apenninic strike-slip. We retrieved 11 focal parameters (including the fault-plane solution) of the 1920 earthquake. Only macroseismic intensity information (from 499 inhabited centres) through the KF-NGA inversion technique was used. This technique uses a Kinematic model of the earthquake source and speeds up the calculation by a Genetic Algorithm with Niching. The result is a pure dip-slip focal solution. The intrinsic ambiguities of the KF-NGA method (±180° on the rake angle; choice of the fault plane between the two nodal planes) were solved with field and seismotectonic evidence. The earthquake was generated by a normal fault (rake angle = 265° ± 8°) with an Apennine direction (114° ± 5°) and dipping 38° ± 6° towards SW. The likely candidate for hosting the source-fault in 1920 is the Compione-Comano fault that borders the NE edge of the Lunigiana graben. The KF-NGA algorithm proved to be invaluable for studying the kinematics of early instrumental earthquakes and allowed us to uniquely individuate, for the first time ever, the seismogenic source of the 1920 earthquake. Our findings have implications in hazard computation and seismotectonic contexts.
    Description: Published
    Description: 1465–1477
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: Inverse theory ; Body waves ; Earthquake source observations ; Seismicity and tectonics ; Dynamics: seismotectonics ; Fractures, faults, and high strain deformation zones ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 33
    Publication Date: 2021-12-22
    Description: Systematic variations in the crystal cargo and whole-rock isotopic compositions of mantle-derived basalts in the intraplate Dunedin Volcano (New Zealand) indicate the influence of a complex mantle-to-crust polybaric plumbing system. Basaltic rocks define a compositional spectrum from low-alkali basalts through mid-alkali basalts to high-alkali basalts. High-alkali basalts display clinopyroxene crystals with sector (hourglass) and oscillatory zoning (Mg#61–82) as well as Fe-rich green cores (Mg#43–69), whereas low-alkali basalts are characterized by clinopyroxenes with unzoned overgrowths (Mg#69–83) on resorbed mafic cores (Mg#78–88), coexisting with reversely zoned plagioclase crystals (An43–68 to An60–84 from core to rim). Complex magma dynamics are indicated by distinctive compositional variations in clinopyroxene phenocrysts, with Cr-rich zones (Mg#74–87) indicating continuous recharge by more mafic magmas. Crystallization of olivine, clinopyroxene and titanomagnetite occurred within a polybaric plumbing system extending from upper mantle to mid-crustal depths (485–1059 MPa and 1147–1286°C), whereas crystallization of plagioclase with subordinate clinopyroxene and titanomagnetite proceeded towards shallower crustal levels. The compositions of high-alkali basalts and mid-alkali basalts resemble those of ocean island basalts and are characterized by FOZO-HIMU isotopic signatures (87Sr/86Sri = 0.70277–0.70315, 143Nd/144Ndi = 0.51286–0.51294 and 206Pb/204Pb = 19.348–20.265), whereas low-alkali basalts have lower incompatible element abundances and isotopic compositions trending towards EMII (87Sr/86Sri = 0.70327–70397, 143Nd/144Ndi = 0.51282–0.51286 and 206Pb/204Pb = 19.278–19.793). High- and mid-alkali basalt magmas mostly crystallized in the lower crust, whereas low-alkali basalt magma recorded deeper upper mantle clinopyroxene crystallization before eruption. The variable alkaline character and isotope composition may result from interaction of low-alkaline melts derived from the asthenosphere with melts derived from lithospheric mantle, possibly initiated by asthenospheric melt percolation. The transition to more alkaline compositions was induced by variable degrees of melting of metasomatic lithologies in the lithospheric mantle, leading to eruption of predominantly small-volume, high-alkali magmas at the periphery of the volcano. Moreover, the lithosphere imposed a filtering effect on the alkalinity of these intraplate magmas. As a consequence, the eruption of low-alkali basalts with greater asthenospheric input was concentrated at the centre of the volcano, where the plumbing system was more developed.
    Description: Published
    Description: egab062
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: alkali basalts ; Dunedin Volcano ; thermobarometry ; primary magma ; lithospheric mantle filter ; Igneous Petrology ; Thermobarometry ; Mantle melting and metasomatism ; Magmatic plumbing systems
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 34
    Publication Date: 2022-02-14
    Description: The influence of the Atlantic multidecadal variability (AMV) on the North Atlantic storm track and eddy-driven jet in the winter season is assessed via a coordinated analysis of idealized simulations with state-of-the-art coupled models. Data used are obtained from a multimodel ensemble of AMV± experiments conducted in the framework of the Decadal Climate Prediction Project component C. These experiments are performed by nudging the surface of the Atlantic Ocean to states defined by the superimposition of observed AMV± anomalies onto the model climatology. A robust extratropical response is found in the form of a wave train extending from the Pacific to the Nordic seas. In the warm phase of the AMV compared to the cold phase, the Atlantic storm track is typically contracted and less extended poleward and the low-level jet is shifted toward the equator in the eastern Atlantic. Despite some robust features, the picture of an uncertain and model-dependent response of the Atlantic jet emerges and we demonstrate a link between model bias and the character of the jet response.
    Description: Published
    Description: 347-360
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 35
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, W. M., Alexander, H., Bier, R. L., Miller, D. R., Muscarella, M. E., Pitz, K. J., & Smith, H. Auxotrophic interactions: A stabilizing attribute of aquatic microbial communities? FEMS Microbiology Ecology, (2020): fiaa115, doi: 10.1093/femsec/fiaa115.
    Description: Auxotrophy, or an organism's requirement for an exogenous source of an organic molecule, is widespread throughout species and ecosystems. Auxotrophy can result in obligate interactions between organisms, influencing ecosystem structure and community composition. We explore how auxotrophy-induced interactions between aquatic microorganisms affect microbial community structure and stability. While some studies have documented auxotrophy in aquatic microorganisms, these studies are not widespread, and we therefore do not know the full extent of auxotrophic interactions in aquatic environments. Current theoretical and experimental work suggests that auxotrophy links microbial community members through a complex web of metabolic dependencies. We discuss the proposed ways in which auxotrophy may enhance or undermine the stability of aquatic microbial communities, highlighting areas where our limited understanding of these interactions prevents us from being able to predict the ecological implications of auxotrophy. Finally, we examine an example of auxotrophy in harmful algal blooms to place this often theoretical discussion in a field context where auxotrophy may have implications for the development and robustness of algal bloom communities. We seek to draw attention to the relationship between auxotrophy and community stability in an effort to encourage further field and theoretical work that explores the underlying principles of microbial interactions.
    Description: This work was supported by the National Science Foundation [OCE-1356192].
    Keywords: Auxotrophy ; Microbial community stability ; Microbial interactions ; Aquatic
    Repository Name: Woods Hole Open Access Server
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  • 36
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Keller, A. G., Apprill, A., Lebaron, P., Robbins, J., Romano, T. A., Overton, E., Rong, Y., Yuan, R., Pollara, S., & Whalen, K. E. Characterizing the culturable surface microbiomes of diverse marine animals. FEMS Microbiology Ecology, 97(4), (2021): fiab040, https://doi.org/10.1093/femsec/fiab040.
    Description: Biofilm-forming bacteria have the potential to contribute to the health, physiology, behavior and ecology of the host and serve as its first line of defense against adverse conditions in the environment. While metabarcoding and metagenomic information furthers our understanding of microbiome composition, fewer studies use cultured samples to study the diverse interactions among the host and its microbiome, as cultured representatives are often lacking. This study examines the surface microbiomes cultured from three shallow-water coral species and two whale species. These unique marine animals place strong selective pressures on their microbial symbionts and contain members under similar environmental and anthropogenic stress. We developed an intense cultivation procedure, utilizing a suite of culture conditions targeting a rich assortment of biofilm-forming microorganisms. We identified 592 microbial isolates contained within 15 bacterial orders representing 50 bacterial genera, and two fungal species. Culturable bacteria from coral and whale samples paralleled taxonomic groups identified in culture-independent surveys, including 29% of all bacterial genera identified in the Megaptera novaeangliae skin microbiome through culture-independent methods. This microbial repository provides raw material and biological input for more nuanced studies which can explore how members of the microbiome both shape their micro-niche and impact host fitness.
    Description: Funding was provided by the National Science Foundation (Biological Oceanography) award #1657808 and National Institutes of Health grants 1R21-AI119311–01 to K. E. Whalen, as well as funding from the Koshland Integrated Natural Science Center and Green Fund at Haverford College. This constitutes scientific manuscript #298 from the Sea Research Foundation.
    Keywords: Bacteria ; SSU rRNA ; Coral ; Whale ; Microbiome ; Skin
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  • 37
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, P., Huang, C., Lin, J., Jian, Z., Sun, Z., & Zhao, M. The South China Sea is not a mini-Atlantic: plate-edge rifting vs intra-plate rifting. National Science Review, 6(5), (2019): 902-913, doi:10.1093/nsr/nwz135.
    Description: The South China Sea, as ‘a non-volcanic passive margin basin’ in the Pacific, has often been considered as a small-scale analogue of the Atlantic. The recent ocean drilling in the northern South China Sea margin found, however, that the Iberian model of non-volcanic rifted margin from the Atlantic does not apply to the South China Sea. In this paper, we review a variety of rifted basins and propose to discriminate two types of rifting basins: plate-edge type such as the South China Sea and intra-plate type like the Atlantic. They not only differ from each other in structure, formation process, lifespan and geographic size, but also occur at different stages of the Wilson cycle. The intra-plate rifting occurred in the Mesozoic and gave rise to large oceans, whereas the plate-edge rifting took place mainly in the mid-Cenozoic, with three-quarters of the basins concentrated in the Western Pacific. As a member of the Western Pacific system of marginal seas, the South China Sea should be studied not in isolation on its origin and evolution, but in a systematic context to include also its neighboring counterparts.
    Description: This work was supported by the National Natural Science Foundation of China as a part of the ‘South China Sea Deep’ Project (91128000).
    Keywords: Rifting ; Marginal basin ; Passive margin ; South China Sea ; Western Pacific ; Subduction
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  • 38
    Publication Date: 2022-10-28
    Description: Relative relocation methods are commonly used to precisely relocate earthquake clusters consisting of similar waveforms. Repeating waveforms are often recorded at volcanoes, where, however, the crust structure is expected to contain strong heterogeneities and therefore the 1D velocity model assumption that is made in most location strategies is not likely to describe reality. A peculiar cluster of repeating low-frequency seismic events was recorded on the south flank of Katla volcano (Iceland) from 2011. As the hypocentres are located at the rim of the glacier, the seismicity may be due to volcanic or glacial processes. Information on the size and shape of the cluster may help constraining the source process. The extreme similarity of waveforms points to a very small spatial distribution of hypocentres. In order to extract meaningful information about size and shape of the cluster, we minimize uncertainty by optimizing the cross-correlation measurements and relative-relocation process. With a synthetic test we determine the best parameters for differential-time measurements and estimate their uncertainties, specifically for each waveform. We design a relocation strategy to work without a predefined velocity model, by formulating and inverting the problem to seek changes in both location and slowness, thus accounting for azimuth, take-off angles and velocity deviations from a 1D model. We solve the inversion explicitly in order to propagate data errors through the calculation. With this approach we are able to resolve a source volume few tens of meters wide on horizontal directions and around 100 meters in depth. There is no suggestion that the hypocentres lie on a single fault plane and the depth distribution indicates that their source is unlikely to be related to glacial processes as the ice thickness is not expected to exceed few tens of meters in the source area.
    Description: Published
    Description: 1244–1257
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Keywords: Physics - Geophysics; Physics - Geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 39
    Publication Date: 2022-12-01
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 103(6), (2022): E1502-E1521, https://doi.org/10.1175/bams-d-21-0227.1.
    Description: Climate observations inform about the past and present state of the climate system. They underpin climate science, feed into policies for adaptation and mitigation, and increase awareness of the impacts of climate change. The Global Climate Observing System (GCOS), a body of the World Meteorological Organization (WMO), assesses the maturity of the required observing system and gives guidance for its development. The Essential Climate Variables (ECVs) are central to GCOS, and the global community must monitor them with the highest standards in the form of Climate Data Records (CDR). Today, a single ECV—the sea ice ECV—encapsulates all aspects of the sea ice environment. In the early 1990s it was a single variable (sea ice concentration) but is today an umbrella for four variables (adding thickness, edge/extent, and drift). In this contribution, we argue that GCOS should from now on consider a set of seven ECVs (sea ice concentration, thickness, snow depth, surface temperature, surface albedo, age, and drift). These seven ECVs are critical and cost effective to monitor with existing satellite Earth observation capability. We advise against placing these new variables under the umbrella of the single sea ice ECV. To start a set of distinct ECVs is indeed critical to avoid adding to the suboptimal situation we experience today and to reconcile the sea ice variables with the practice in other ECV domains.
    Description: PH’s contribution was funded under the Australian Government’s Antarctic Science Collaboration Initiative program, and contributes to Project 6 of the Australian Antarctic Program Partnership (ASCI000002). PH acknowledges support through the Australian Antarctic Science Projects 4496 and 4506, and the International Space Science Institute (Bern, Switzerland) project #405.
    Description: 2022-12-01
    Keywords: Sea ice ; Climate change ; Climatology ; Climate records
    Repository Name: Woods Hole Open Access Server
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  • 40
    Publication Date: 2022-11-10
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sassenhagen, I., Erdner, D., Lougheed, B., Richlen, M., & SjÖqvist, C. Estimating genotypic richness and proportion of identical multi-locus genotypes in aquatic microalgal populations. Journal of Plankton Research, 44(4), (2022): 559-572, https://doi.org/10.1093/plankt/fbac034.
    Description: The majority of microalgal species reproduce asexually, yet population genetic studies rarely find identical multi-locus genotypes (MLG) in microalgal blooms. Instead, population genetic studies identify large genotypic diversity in most microalgal species. This paradox of frequent asexual reproduction but low number of identical genotypes hampers interpretations of microalgal genotypic diversity. We present a computer model for estimating, for the first time, the number of distinct MLGs by simulating microalgal population composition after defined exponential growth periods. The simulations highlighted the effects of initial genotypic diversity, sample size and intraspecific differences in growth rates on the probability of isolating identical genotypes. We estimated the genotypic richness for five natural microalgal species with available high-resolution population genetic data and monitoring-based growth rates, indicating 500 000 to 2 000 000 distinct genotypes for species with few observed clonal replicates (〈5%). Furthermore, our simulations indicated high variability in genotypic richness over time and among microalgal species. Genotypic richness was also strongly impacted by intraspecific variability in growth rates. The probability of finding identical MLGs and sampling a representative fraction of genotypes decreased noticeably with smaller sample sizes, challenging the detection of differences in genotypic diversity with typical isolate numbers in the field.
    Description: This work was supported by the Olle Engkvist foundation [200-0564 to I.S.]; the Swedish Research Council (Vetenskapsrådet) [2018-04992 to B.C.L.]; the Academy of Finland [321609 to C.S.]; the National Science Foundation [NSF OCE-1841811 to D.L.E. and M.L.R.]; and the National Institute of Environmental Health [NIEHS P01ES028949 to M.L.R.].
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  • 41
    Publication Date: 2022-11-27
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(6), (2022): 1233-1244, https://doi.org/10.1175/jpo-d-21-0223.1.
    Description: The Sverdrup relation is the backbone of wind-driven circulation theory; it is a simple relation between the meridional transport of the wind-driven circulation in the upper ocean and the wind stress curl. However, the relation is valid for steady circulation only. In this study, a time-dependent Sverdrup relation is postulated, in which the meridional transport in a time-dependent circulation is the sum of the local wind stress curl term and a time-delayed term representing the effect of the eastern boundary condition. As an example, this time-dependent Sverdrup relation is evaluated through its application to the equatorial circulation in the Indian Ocean, using reanalysis data and a reduced gravity model. Close examination reveals that the southward Somali Current occurring during boreal winter is due to the combination of the local wind stress curl in the Arabian Sea and delayed signals representing the time change of layer thickness at the eastern boundary.
    Description: This work is supported by NSFC (41822602, 41976016, 42005035, 42076021), the Strategic Priority Research Program of Chinese Academy of Sciences (XDB42000000, XDA 20060502), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0306), Guangdong Basic and Applied Basic Research Foundation (2021A1515011534), Youth Innovation Promotion Association CAS, ISEE2021ZD01, and LTOZZ2002. The numerical simulation is supported by the High-Performance Computing Division in the South China Sea Institute of Oceanology.
    Description: 2022-11-27
    Keywords: Ocean circulation ; Ocean dynamics ; Rossby waves ; Wind stress curl
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  • 42
    Publication Date: 2022-12-09
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(7), (2022): 1333-1350, https://doi.org/10.1175/jpo-d-21-0298.1.
    Description: Idealized numerical simulations were conducted to investigate the influence of channel curvature on estuarine stratification and mixing. Stratification is decreased and tidal energy dissipation is increased in sinuous estuaries compared to straight channel estuaries. We applied a vertical salinity variance budget to quantify the influence of straining and mixing on stratification. Secondary circulation due to the channel curvature is found to affect stratification in sinuous channels through both lateral straining and enhanced vertical mixing. Alternating negative and positive lateral straining occur in meanders upstream and downstream of the bend apex, respectively, corresponding to the normal and reversed secondary circulation with curvature. The vertical mixing is locally enhanced in curved channels with the maximum mixing located upstream of the bend apex. Bend-scale bottom salinity fronts are generated near the inner bank upstream of the bend apex as a result of interaction between the secondary flow and stratification. Shear mixing at bottom fronts, instead of overturning mixing by the secondary circulation, provides the dominant mechanism for destruction of stratification. Channel curvature can also lead to increased drag, and using a Simpson number with this increased drag coefficient can relate the decrease in stratification with curvature to the broader estuarine parameter space.
    Description: The research leading to these results was funded by NSF Awards OCE-1634481 and OCE-2123002.
    Description: 2022-12-09
    Keywords: Estuaries ; Mixing ; Secondary circulation ; Fronts ; Tides ; Numerical analysis/modeling
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  • 43
    Publication Date: 2022-12-16
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(7), (2022): 1415–1430. https://doi.org/10.1175/JPO-D-21-0147.1.
    Description: Strong subinertial variability near a seamount at the Xisha Islands in the South China Sea was revealed by mooring observations from January 2017 to January 2018. The intraseasonal deep flows presented two significant frequency bands, with periods of 9–20 and 30–120 days, corresponding to topographic Rossby waves (TRWs) and deep eddies, respectively. The TRW and deep eddy signals explained approximately 60% of the kinetic energy of the deep subinertial currents. The TRWs at the Ma, Mb, and Mc moorings had 297, 262, and 274 m vertical trapping lengths, and ∼43, 38, and 55 km wavelengths, respectively. Deep eddies were independent from the upper layer, with the largest temperature anomaly being 〉0.4°C. The generation of the TRWs was induced by mesoscale perturbations in the upper layer. The interaction between the cyclonic–anticyclonic eddy pair and the seamount topography contributed to the generation of deep eddies. Owing to the potential vorticity conservation, the westward-propagating tilted interface across the eddy pair squeezed the deep-water column, thereby giving rise to negative vorticity west of the seamount. The strong front between the eddy pair induced a northward deep flow, thereby generating a strong horizontal velocity shear because of lateral friction and enhanced negative vorticity. Approximately 4 years of observations further confirmed the high occurrence of TRWs and deep eddies. TRWs and deep eddies might be crucial for deep mixing near rough topographies by transferring mesoscale energy to small scales.
    Description: This work was supported by the National Natural Science Foundation of China (92158204, 91958202, 42076019, 41776036, 91858203), the Open Project Program of State Key Laboratory of Tropical Oceanography (project LTOZZ2001), and Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0304).
    Description: 2022-12-16
    Keywords: Abyssal circulation ; Ocean circulation ; Ocean dynamics ; Intraseasonal variability
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  • 44
    Publication Date: 2022-12-21
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(12), (2022): 2923–2933, https://doi.org/10.1175/jpo-d-22-0064.1.
    Description: The characteristics and dynamics of depth-average along-shelf currents at monthly and longer time scales are examined using 17 years of observations from the Martha’s Vineyard Coastal Observatory on the southern New England inner shelf. Monthly averages of the depth-averaged along-shelf current are almost always westward, with the largest interannual variability in winter. There is a consistent annual cycle with westward currents of 5 cm s−1 in summer decreasing to 1–2 cm s−1 in winter. Both the annual cycle and interannual variability in the depth-average along-shelf current are predominantly driven by the along-shelf wind stress. In the absence of wind forcing, there is a westward flow of ∼5 cm s−1 throughout the year. At monthly time scales, the depth-average along-shelf momentum balance is primarily between the wind stress, surface gravity wave–enhanced bottom stress, and an opposing pressure gradient that sets up along the southern New England shelf in response to the wind. Surface gravity wave enhancement of bottom stress is substantial over the inner shelf and is essential to accurately estimating the bottom stress variation across the inner shelf.
    Description: The National Science Foundation, Woods Hole Oceanographic Institution, the Massachusetts Technology Collaborative, and the Office of Naval Research have supported the construction and maintenance of MVCO. The analysis presented here was partially funded by the National Science Foundation under Grants OCE 1558874 and OCE 1655686.
    Keywords: Continental shelf/slope ; Coastal flows ; Momentum ; Ocean dynamics ; Wind stress
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  • 45
    Publication Date: 2022-12-21
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(12), (2022): 2909-2921, https://doi.org/10.1175/jpo-d-22-0063.1.
    Description: A remarkably consistent Lagrangian upwelling circulation at monthly and longer time scales is observed in a 17-yr time series of current profiles in 12 m of water on the southern New England inner shelf. The upwelling circulation is strongest in summer, with a current magnitude of ∼1 cm s−1, which flushes the inner shelf in ∼2.5 days. The average winter upwelling circulation is about one-half of the average summer upwelling circulation, but with larger month-to-month variations driven, in part, by cross-shelf wind stresses. The persistent upwelling circulation is not wind-driven; it is driven by a cross-shelf buoyancy force associated with less-dense water near the coast. The cross-shelf density gradient is primarily due to temperature in summer, when strong surface heating warms shallower nearshore water more than deeper offshore water, and to salinity in winter, caused by fresher water near the coast. In the absence of turbulent stresses, the cross-shelf density gradient would be in a geostrophic, thermal-wind balance with the vertical shear in the along-shelf current. However, turbulent stresses over the inner shelf attributable to strong tidal currents and wind stress cause a partial breakdown of the thermal-wind balance that releases the buoyancy force, which drives the observed upwelling circulation. The presence of a cross-shelf density gradient has a profound impact on exchange across this inner shelf. Many inner shelves are characterized by turbulent stresses and cross-shelf density gradients with lighter water near the coast, suggesting turbulent thermal-wind-driven coastal upwelling may be a broadly important cross-shelf exchange mechanism.
    Description: The National Science Foundation, Woods Hole Oceanographic Institution, the Massachusetts Technology Collaborative, and the Office of Naval Research have supported the construction and maintenance of MVCO. The analysis presented here was partially funded by the National Science Foundation under Grants OCE 1558874 and OCE 1655686.
    Keywords: Buoyancy ; Coastal flows ; Currents ; Dynamics ; Lagrangian circulation/transport ; Upwelling/downwelling
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  • 46
    Publication Date: 2022-06-21
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(6),(2022): 1191-1204, https://doi.org/10.1175/jpo-d-21-0242.1.
    Description: A simplified quasigeostrophic (QG) analytical model together with an idealized numerical model are used to study the effect of uneven ice–ocean stress on the temporal evolution of the geostrophic current under sea ice. The tendency of the geostrophic velocity in the QG model is given as a function of the lateral gradient of vertical velocity and is further related to the ice–ocean stress with consideration of a surface boundary layer. Combining the analytical and numerical solutions, we demonstrate that the uneven stress between the ice and an initially surface-intensified, laterally sheared geostrophic current can drive an overturning circulation to trigger the displacement of isopycnals and modify the vertical structure of the geostrophic velocity. When the near-surface isopycnals become tilted in the opposite direction to the deeper ones, a subsurface velocity core is generated (via geostrophic setup). This mechanism should help understand the formation of subsurface currents in the edge of Chukchi and Beaufort Seas seen in observations. Furthermore, our solutions reveal a reversed flow extending from the bottom to the middepth, suggesting that the ice-induced overturning circulation potentially influences the currents in the deep layers of the Arctic Ocean, such as the Atlantic Water boundary current.
    Description: This work was funded by the National Key Research and Development Program of China (Grant 2017YFA0604600), the National Natural Science Foundation of China (Grant 41676019), the Fundamental Research Funds for the Central Universities (Grant 2019B81214), the Postgraduate Research and Practice Innovation Program of Jiangsu Province (Grant KYCX19_0384), and the National Science Foundation (MAS, Grants OPP-1822334, OCE-2122633).
    Keywords: Arctic ; Sea ice ; Channel flows ; Vertical motion ; Ekman pumping ; Idealized models ; Quasigeostrophic models
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  • 47
    Publication Date: 2022-06-24
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Page, H. N., Bahr, K. D., Cyronak, T., Jewett, E. B., Johnson, M. D., & McCoy, S. J. Responses of benthic calcifying algae to ocean acidification differ between laboratory and field settings. Ices Journal of Marine Science, 79(1), (2022): 1–11, https://doi.org/10.1093/icesjms/fsab232.
    Description: Accurately predicting the effects of ocean and coastal acidification on marine ecosystems requires understanding how responses scale from laboratory experiments to the natural world. Using benthic calcifying macroalgae as a model system, we performed a semi-quantitative synthesis to compare directional responses between laboratory experiments and field studies. Variability in ecological, spatial, and temporal scales across studies, and the disparity in the number of responses documented in laboratory and field settings, make direct comparisons difficult. Despite these differences, some responses, including community-level measurements, were consistent across laboratory and field studies. However, there were also mismatches in the directionality of many responses with more negative acidification impacts reported in laboratory experiments. Recommendations to improve our ability to scale responses include: (i) developing novel approaches to allow measurements of the same responses in laboratory and field settings, and (ii) researching understudied calcifying benthic macroalgal species and responses. Incorporating these guidelines into research programs will yield data more suitable for robust meta-analyses and will facilitate the development of ecosystem models that incorporate proper scaling of organismal responses to in situ acidification. This, in turn, will allow for more accurate predictions of future changes in ecosystem health and function in a rapidly changing natural climate.
    Description: We would like to thank the Ocean Carbon and Biogeochemistry Program for organizing the fourth U.S. Ocean Acidification Principal Investigators meeting, which is where this synthesis was conceived. HNP was a postdoctoral research fellow at Mote Marine Laboratory. MDJ is a postdoctoral scholar at Woods Hole Oceanographic Institution. SJM is a Norma J. Lang early career fellow of the Phycological Society of America.
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  • 48
    Publication Date: 2022-06-22
    Description: In this paper we simulate the earthquake that hit the city of L'Aquila on the 6th of April 2009 using SPEED (SPectral Elements in Elastodynamics with Discontinuous Galerkin), an open-source code able to simulate the propagation of seismic waves in complex three-dimensional (3D) domains. Our model includes an accurate 3D recon- struction of the Quaternary deposits, according to the most up-to-date data obtained from the Microzonation studies in Central Italy and a detailed model of the topography incorporated using a newly developed tool (May et al. 2021). The sensitivity of our results with respect to dfferent kinematic seismic sources is inves- tigated. The results obtained are in good agreement with the recordings at the available seismic stations at epicentral distances within a range of 20km. Finally, a blind source prediction scenario application shows a reasonably good agreement between simulations and recordings can be obtained by simulating stochastic rupture realizations with basic input data. These results, although limited to nine simulated scenarios, demonstrate that it is possible to obtain a satisfactory reconstruction of a ground shaking scenario employing a stochastic source constrained on a limited amount of ex-ante information. A similar approach can be used to model future and past earthquakes for which little or no information is typically available, with potential relevant implications for seismic risk assessment.
    Description: Published
    Description: 29–49
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 49
    Publication Date: 2022-06-22
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2022. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: On 29 December 2020, a shallow earthquake of magnitude Mw 6.4 struck northern Croatia, near the town of Petrinja, more than 24 hours after a strong foreshock (Ml 5). We formed a reconnaissance team of European geologists and engineers, from Croatia, Slovenia, France, Italy and Greece, rapidly deployed in the field to map the evidence of coseismic environmental effects. In the epicentral area, we recognized surface deformation, such as tectonic breaks along the earthquake source at the surface, liquefaction features (scattered in the fluvial plains of Kupa, Glina and Sava rivers), and slope failures, both caused by strong motion. Thanks to this concerted, collective and meticulous work, we were able to document and map a clear and unambiguous coseismic surface rupture associated with the main shock. The surface rupture appears discontinuous, consisting of multi-kilometer en échelon right stepping sections, along a NW-SE striking fault that we call the Petrinja-Pokupsko Fault (PPKF). The observed deformation features, in terms of kinematics and trace alignments, are consistent with slip on a right lateral fault, in agreement with the focal solution of the main shock. We found mole tracks, displacement on faults affecting natural features (e. g. drainage channels), scarplets, and more frequently breaks of anthropogenic markers (roads, fences). The surface rupture is observed over a length of ∼13 km from end-to-end, with a maximum displacement of 38 cm, and an average displacement of ∼10 cm. Moreover, the liquefaction extends over an area of nearly 600 km² around the epicenter. Typology of liquefaction features include sand blows, lateral spreading phenomenon along the road and river embankments, as well as sand ejecta of different grain size and matrix. Development of large and long fissures along the fluvial landforms, current or ancient, with massive ejections of sediments is pervasive. These features are sometimes accompanied by small horizontal displacements. Finally, the environmental effects of the earthquake appear to be reasonably consistent with the usual scaling relationships, in particular the surface faulting. This rupture of the ground occurred on or near traces of a fault that shows clear evidence of Quaternary activity. Further and detailed studies will be carried out to characterize this source and related faults in terms of future large earthquakes potential, for their integration into seismic hazard models.
    Description: Published
    Description: 1394–1418
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: Seismicity and tectonics ; Earthquake hazards ; Coseismic effects ; M6.4 Petrinja earthquake (Croatia)
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 50
    Publication Date: 2022-09-01
    Description: In the last years the scientific literature has been enriched with new models of the Moho depth in the Antarctica Continent derived by the seismic reflection technique and refraction profiles, receiver functions and seismic surface waves, but also by gravimetric observations over the continent. In particular, the gravity satellite missions of the last two decades have provided data in this remote region of the Earth and have allowed the investigation of the crust properties. Meanwhile, other important contributions in this direction has been given by the fourth International Polar Year (IPY, 2007–2008) which started seismographic and geodetic networks of unprecedented duration and scale, including airborne gravimetry over largely unexplored Antarctic frontiers. In this study, a new model for the Antarctica Moho depths is proposed. This new estimation is based on no satellite gravity measures, thanks to the availability of the gravity database ANTGG2015, that collects gravity data from ground-base, airborne and shipborne campaigns. In this new estimate of the Moho depths the contribution of the gravity measures has been maximized reducing any correction of the gravity measures and avoiding constraints of the solution to seismological observations and to geological evidence. With this approach a pure gravimetric solution has been determined. The model obtained is pretty in agreement with other Moho models and thanks to the use of independent data it can be exploited also for cross-validating different Moho depths solutions.
    Description: Published
    Description: 1404–1420
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Antarctica ; Moho ; Gravity inversion ; Collocation ; ANTGG2015
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  • 51
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    Oxford University Press
    In:  EPIC3Geophysical Journal International, Oxford University Press, 231, pp. 1959-1981
    Publication Date: 2022-09-16
    Description: Seismic reflection and refraction data were collected in 2007 and 2012 to reveal the crustal fabric on a single long composite profile offshore Prydz Bay, East Antarctica. A P-wave velocity model provides insights on the crustal fabric, and a gravity-constrained density model is used to describe the crustal and mantle structure. The models show that a 230-km- wide continent–ocean transition separates stretched continental from oceanic crust along our profile. While the oceanic crust close to the continent–ocean boundary is just 3.5–5 km thick, its thickness increases northwards towards the Southern Kerguelen Plateau to 12 km. This change is accompanied by thickening of a lower crustal layer with high P-wave velocities of up to 7.5 km s–1, marking intrusive rocks emplaced beneath the mid-ocean ridge under increasing influence of the Kerguelen plume. Joint interpretations of our crustal model, seismic reflection data and magnetic data sets constrain the age and extent of oceanic crust in the research area. Oceanic crust is shown to continue to around 160 km farther south than has been interpreted in previous data, with profound implications for plate kinematic models of the region. Finally, by combining our findings with a regional magnetic data compilation and regional seismic reflection data we propose a larger extent of oceanic crust in the Enderby Basin than previously known.
    Repository Name: EPIC Alfred Wegener Institut
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  • 52
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Renfrew, I. A., Pickart, R. S., Vage, K., Moore, G. W. K., Bracegirdle, T. J., Elvidge, A. D., Jeansson, E., Lachlan-Cope, T., McRaven, L. T., Papritz, L., Reuder, J., Sodemann, H., Terpstra, A., Waterman, S., Valdimarsson, H., Weiss, A., Almansi, M., Bahr, F., Brakstad, A., Barrell, C., Brooke, J. K., Brooks, B. J., Brooks, I. M., Brooks, M. E., Bruvik, E. M., Duscha, C., Fer, I., Golid, H. M., Hallerstig, M., Hessevik, I., Huang, J., Houghton, L., Jonsson, S., Jonassen, M., Jackson, K., Kvalsund, K., Kolstad, E. W., Konstali, K., Kristiansen, J., Ladkin, R., Lin, P., Macrander, A., Mitchell, A., Olafsson, H., Pacini, A., Payne, C., Palmason, B., Perez-Hernandez, M. D., Peterson, A. K., Petersen, G. N., Pisareva, M. N., Pope, J. O., Seidl, A., Semper, S., Sergeev, D., Skjelsvik, S., Soiland, H., Smith, D., Spall, M. A., Spengler, T., Touzeau, A., Tupper, G., Weng, Y., Williams, K. D., Yang, X., & Zhou, S. The Iceland Greenland Seas Project. Bulletin of the American Meteorological Society, 100(9), (2019): 1795-1817, doi:10.1175/BAMS-D-18-0217.1.
    Description: The Iceland Greenland Seas Project (IGP) is a coordinated atmosphere–ocean research program investigating climate processes in the source region of the densest waters of the Atlantic meridional overturning circulation. During February and March 2018, a field campaign was executed over the Iceland and southern Greenland Seas that utilized a range of observing platforms to investigate critical processes in the region, including a research vessel, a research aircraft, moorings, sea gliders, floats, and a meteorological buoy. A remarkable feature of the field campaign was the highly coordinated deployment of the observing platforms, whereby the research vessel and aircraft tracks were planned in concert to allow simultaneous sampling of the atmosphere, the ocean, and their interactions. This joint planning was supported by tailor-made convection-permitting weather forecasts and novel diagnostics from an ensemble prediction system. The scientific aims of the IGP are to characterize the atmospheric forcing and the ocean response of coupled processes; in particular, cold-air outbreaks in the vicinity of the marginal ice zone and their triggering of oceanic heat loss, and the role of freshwater in the generation of dense water masses. The campaign observed the life cycle of a long-lasting cold-air outbreak over the Iceland Sea and the development of a cold-air outbreak over the Greenland Sea. Repeated profiling revealed the immediate impact on the ocean, while a comprehensive hydrographic survey provided a rare picture of these subpolar seas in winter. A joint atmosphere–ocean approach is also being used in the analysis phase, with coupled observational analysis and coordinated numerical modeling activities underway.
    Description: The IGP has received funding from the U.S. National Science Foundation: Grant OCE-1558742; the U.K.’s Natural Environment Research Council: AFIS (NE/N009754/1); the Research Council of Norway: MOCN (231647), VENTILATE (229791), SNOWPACE (262710) and FARLAB (245907); and the Bergen Research Foundation (BFS2016REK01). We thank all those involved in the field work associated with the IGP, particularly the officers and crew of the Alliance, and the operations staff of the aircraft campaign.
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  • 53
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lasek-Nesselquist, E., & Johnson, M. D. A phylogenomic approach to clarifying the relationship of Mesodinium within the Ciliophora: a case study in the complexity of mixed-species transcriptome analyses. Genome Biology and Evolution, 11(11), (2019): 3218–3232, doi:10.1093/gbe/evz233.
    Description: Recent high-throughput sequencing endeavors have yielded multigene/protein phylogenies that confidently resolve several inter- and intra-class relationships within the phylum Ciliophora. We leverage the massive sequencing efforts from the Marine Microbial Eukaryote Transcriptome Sequencing Project, other SRA submissions, and available genome data with our own sequencing efforts to determine the phylogenetic position of Mesodinium and to generate the most taxonomically rich phylogenomic ciliate tree to date. Regardless of the data mining strategy, the multiprotein data set, or the molecular models of evolution employed, we consistently recovered the same well-supported relationships among ciliate classes, confirming many of the higher-level relationships previously identified. Mesodinium always formed a monophyletic group with members of the Litostomatea, with mixotrophic species of Mesodinium—M. rubrum, M. major, and M. chamaeleon—being more closely related to each other than to the heterotrophic member, M. pulex. The well-supported position of Mesodinium as sister to other litostomes contrasts with previous molecular analyses including those from phylogenomic studies that exploited the same transcriptomic databases. These topological discrepancies illustrate the need for caution when mining mixed-species transcriptomes and indicate that identifying ciliate sequences among prey contamination—particularly for Mesodinium species where expression from stolen prey nuclei appears to dominate—requires thorough and iterative vetting with phylogenies that incorporate sequences from a large outgroup of prey.
    Description: We thank David Beaudoin and Holly V. Moeller for their assistance in collecting cells and extracting RNA. We thank the Josephine Bay Paul Center for Comparative Molecular Biology and Evolution at the Marine Biological Laboratory for the generous use of their servers. This work was supported in part by a National Science Foundation grant to both authors (IOS 1354773).
    Keywords: Mesodinium ; Litostomatea ; ciliate phylogenomics ; mixed-species transcriptomes ; sequence contamination
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  • 54
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(12), (2019): 3127-3143, doi: 10.1175/JPO-D-19-0011.1.
    Description: The Intermediate Western Boundary Current (IWBC) transports Antarctic Intermediate Water across the Vitória–Trindade Ridge (VTR), a seamount chain at ~20°S off Brazil. Recent studies suggest that the IWBC develops a strong cyclonic recirculation in Tubarão Bight, upstream of the VTR, with weak time dependency. We herein use new quasi-synoptic observations, data from the Argo array, and a regional numerical model to describe the structure and variability of the IWBC and to investigate its dynamics. Both shipboard acoustic Doppler current profiler (ADCP) data and trajectories of Argo floats confirm the existence of the IWBC recirculation, which is also captured by our Regional Oceanic Modeling System (ROMS) simulation. An “intermediate-layer” quasigeostrophic (QG) model indicates that the ROMS time-mean flow is a good proxy for the IWBC steady state, as revealed by largely parallel isolines of streamfunction ψ⎯ and potential vorticity Q⎯; a ψ⎯−Q⎯ scatter diagram also shows that the IWBC is potentially unstable. Further analysis of the ROMS simulation reveals that remotely generated, westward-propagating nonlinear eddies are the main source of variability in the region. These eddies enter the domain through the Tubarão Bight eastern edge and strongly interact with the IWBC. As they are advected downstream and negotiate the local topography, the eddies grow explosively through horizontal shear production.
    Description: We thank Frank O. Smith for copy editing and proofreading this manuscript. This study was financed in part by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES, Brazil—Finance Code 001 and by Projeto REMARSUL (Processo CAPES 88882.158621/2014-01), Projeto VT-Dyn (Processo FAPESP 2015/21729-4) and Projeto SUBMESO (Processo CNPq 442926/2015-4). Rocha was supported by a WHOI Postdoctoral Scholarship.
    Description: 2020-06-06
    Keywords: South Atlantic Ocean ; Instability ; Mesoscale processes ; Intermediate waters ; In situ oceanic observations ; Quasigeostrophic models
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  • 55
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kwon, Y., Seo, H., Ummenhofer, C. C., & Joyce, T. M. Impact of multidecadal variability in Atlantic SST on winter atmospheric blocking. Journal of Climate, 33(3), (2020): 867-892, doi: 10.1175/JCLI-D-19-0324.1.
    Description: Recent studies have suggested that coherent multidecadal variability exists between North Atlantic atmospheric blocking frequency and the Atlantic multidecadal variability (AMV). However, the role of AMV in modulating blocking variability on multidecadal times scales is not fully understood. This study examines this issue primarily using the NOAA Twentieth Century Reanalysis for 1901–2010. The second mode of the empirical orthogonal function for winter (December–March) atmospheric blocking variability in the North Atlantic exhibits oppositely signed anomalies of blocking frequency over Greenland and the Azores. Furthermore, its principal component time series shows a dominant multidecadal variability lagging AMV by several years. Composite analyses show that this lag is due to the slow evolution of the AMV sea surface temperature (SST) anomalies, which is likely driven by the ocean circulation. Following the warm phase of AMV, the warm SST anomalies emerge in the western subpolar gyre over 3–7 years. The ocean–atmosphere interaction over these 3–7-yr periods is characterized by the damping of the warm SST anomalies by the surface heat flux anomalies, which in turn reduce the overall meridional gradient of the air temperature and thus weaken the meridional transient eddy heat flux in the lower troposphere. The anomalous transient eddy forcing then shifts the eddy-driven jet equatorward, resulting in enhanced Rossby wave breaking and blocking on the northern flank of the jet over Greenland. The opposite is true with the AMV cold phases but with much shorter lags, as the evolution of SST anomalies differs in the warm and cold phases.
    Description: We gratefully acknowledge support from the NSF Climate and Large-scale Dynamics Program (AGS-1355339) to Y-OK, HS, CCU, and TMJ, the NASA Physical Oceanography Program (NNX13AM59G) to Y-OK, HS, and TMJ, NOAA CPO Climate Variability and Predictability Program (NA13OAR4310139) and DOE CESD Regional and Global Model Analysis Program (DE-SC0019492) to Y-OK, and NSF Physical Oceanography Program (OCE-1419235) to HS. We are very grateful to the three anonymous reviewers and editor Dr. Mingfang Ting, for their thorough and insightful suggestions. The NOAA 20CR dataset was downloaded from the NOAA Earth System Research Laboratory Physical Science Division webpage (https://www.esrl.noaa.gov/psd/data/20thC_Rean/). Support for the 20CR Project version 2c dataset is provided by the U.S. Department of Energy, Office of Science Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office. The HadISST dataset was downloaded from the U.K. Met Office Hadley Centre webpage (https://www.metoffice.gov.uk/hadobs/hadisst/). The ERA-20C dataset was downloaded from the ECMWF webpage (https://apps.ecmwf.int/datasets/data/era20c-daily/). The ERSST5 dataset was provided by the NOAA Earth System Research Laboratory Physical Science Division (https://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.v5.html).
    Keywords: North Atlantic Ocean ; Atmosphere-ocean interaction ; Blocking ; Climate variability ; Multidecadal variability ; North Atlantic Oscillation
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  • 56
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(2), (2020): 415-437, doi:10.1175/JPO-D-19-0019.1.
    Description: Results are presented from two dye release experiments conducted in the seasonal thermocline of the Sargasso Sea, one in a region of low horizontal strain rate (~10−6 s−1), the second in a region of intermediate horizontal strain rate (~10−5 s−1). Both experiments lasted ~6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from the two experiments were κz = (2–5) × 10−6 m2 s−1, while isopycnal diffusivities were κH = (0.2–3) m2 s−1, with the range in κH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ~5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (intermediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km. Early surveys from both experiments showed patchy distributions indicative of small-scale stirring at scales of order a few hundred meters. Later surveys show relatively smooth, coherent distributions with only occasional patchiness, suggestive of a diffusive rather than stirring process at the scales of the now larger patches. Together the two experiments provide important clues as to the rates and underlying processes driving diapycnal and isopycnal mixing at these scales.
    Description: Results are presented from two dye release experiments conducted in the seasonal thermocline of the Sargasso Sea, one in a region of low horizontal strain rate (~10−6 s−1), the second in a region of intermediate horizontal strain rate (~10−5 s−1). Both experiments lasted ~6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from the two experiments were κz = (2–5) × 10−6 m2 s−1, while isopycnal diffusivities were κH = (0.2–3) m2 s−1, with the range in κH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ~5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (intermediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km. Early surveys from both experiments showed patchy distributions indicative of small-scale stirring at scales of order a few hundred meters. Later surveys show relatively smooth, coherent distributions with only occasional patchiness, suggestive of a diffusive rather than stirring process at the scales of the now larger patches. Together the two experiments provide important clues as to the rates and underlying processes driving diapycnal and isopycnal mixing at these scales.
    Description: 2020-08-06
    Keywords: Ocean ; Atlantic Ocean ; Diapycnal mixing ; Diffusion ; Dispersion ; Mixing
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  • 57
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Xu, X., Li, G., Li, C., Zhang, J., Wang, Q., Simmons, D. K., Chen, X., Wijesena, N., Zhu, W., Wang, Z., Wang, Z., Ju, B., Ci, W., Lu, X., Yu, D., Wang, Q., Aluru, N., Oliveri, P., Zhang, Y. E., Martindale, M. Q., & Liu, J. Evolutionary transition between invertebrates and vertebrates via methylation reprogramming in embryogenesis. National Science Review, 6(5), (2019):993-1003, doi:10.1093/nsr/nwz064.
    Description: Major evolutionary transitions are enigmas, and the most notable enigma is between invertebrates and vertebrates, with numerous spectacular innovations. To search for the molecular connections involved, we asked whether global epigenetic changes may offer a clue by surveying the inheritance and reprogramming of parental DNA methylation across metazoans. We focused on gametes and early embryos, where the methylomes are known to evolve divergently between fish and mammals. Here, we find that methylome reprogramming during embryogenesis occurs neither in pre-bilaterians such as cnidarians nor in protostomes such as insects, but clearly presents in deuterostomes such as echinoderms and invertebrate chordates, and then becomes more evident in vertebrates. Functional association analysis suggests that DNA methylation reprogramming is associated with development, reproduction and adaptive immunity for vertebrates, but not for invertebrates. Interestingly, the single HOX cluster of invertebrates maintains unmethylated status in all stages examined. In contrast, the multiple HOX clusters show dramatic dynamics of DNA methylation during vertebrate embryogenesis. Notably, the methylation dynamics of HOX clusters are associated with their spatiotemporal expression in mammals. Our study reveals that DNA methylation reprogramming has evolved dramatically during animal evolution, especially after the evolutionary transitions from invertebrates to vertebrates, and then to mammals.
    Description: This work was supported by the National Key Research and Development Program of China (2018YFC1003303), the Strategic Priority Research Program of the CAS (XDB13040200), the National Natural Science Foundation of China (91519306, 31425015), the Youth Innovation Promotion Association of the CAS and the Key Research Program of Frontier Sciences, CAS (QYZDY-SSW-SMC016).
    Keywords: DNA methylation ; evolution ; development ; reprogramming
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  • 58
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 37(5), (2020): 789-806, doi:10.1175/JTECH-D-18-0244.1.
    Description: Realistic ocean state prediction and its validation rely on the availability of high quality in situ observations. To detect data errors, adequate quality check procedures must be designed. This paper presents procedures that take advantage of the ever-growing observation databases that provide climatological knowledge of the ocean variability in the neighborhood of an observation location. Local validity intervals are used to estimate binarily whether the observed values are considered as good or erroneous. Whereas a classical approach estimates validity bounds from first- and second-order moments of the climatological parameter distribution, that is, mean and variance, this work proposes to infer them directly from minimum and maximum observed values. Such an approach avoids any assumption of the parameter distribution such as unimodality, symmetry around the mean, peakedness, or homogeneous distribution tail height relative to distribution peak. To reach adequate statistical robustness, an extensive manual quality control of the reference dataset is critical. Once the data have been quality checked, the local minima and maxima reference fields are derived and the method is compared with the classical mean/variance-based approach. Performance is assessed in terms of statistics of good and bad detections. It is shown that the present size of the reference datasets allows the parameter estimates to reach a satisfactory robustness level to always make the method more efficient than the classical one. As expected, insufficient robustness persists in areas with an especially low number of samples and high variability.
    Description: This study has been conducted using EU Copernicus Marine Service Information and was supported by the European Union within the EU Copernicus Marine Service In Situ phase-I and phase-II contracts led by Ifremer. The publication was also supported by SOERE CTDO2 in France. The Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (see http://www.argo.ucsd.edu, http://argo.jcommops.org). The Argo Program is part of the Global Ocean Observing System (http://doi.org/10.17882/42182). The marine mammal data were collected and made freely available by the International MEOP Consortium and the national programs that contribute to it (see http://www.meop.net; https://doi.org/10.17882/45461). Aleix Gelabert and Dídac Costa were the skippers of the OPOO, sponsored by the Intergovernmental Oceanographic Commission (UNESCO) and Pharmaton. The BWR is a periodic oceanic race organized by the Fundació Navegació Oceànica de Barcelona (FNOB). Reviewer D. Briand provided some useful comments on the final version of the draft paper before submission.
    Description: 2020-11-04
    Keywords: Ocean ; Climatology ; Salinity ; Temperature ; Data quality control ; Oceanic variability
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  • 59
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(5), (2020): 1245-1263, doi:10.1175/JPO-D-19-0213.1.
    Description: We use laboratory experiments and theoretical modeling to investigate the surface expression of a subglacial discharge plume, as occurs at many fjords around Greenland. The experiments consider a fountain that is released vertically into a homogeneous fluid, adjacent either to a vertical or a sloping wall, that then spreads horizontally at the free surface before sinking back to the bottom. We present a model that separates the fountain into two separate regions: a vertical fountain and a horizontal, negatively buoyant jet. The model is compared to laboratory experiments that are conducted over a range of volume fluxes, density differences, and ambient fluid depths. It is shown that the nondimensionalized length, width, and aspect ratio of the surface expression are dependent on the Froude number, calculated at the start of the negatively buoyant jet. The model is applied to observations of the surface expression from a Greenland subglacial discharge plume. In the case where the discharge plume reaches the surface with negative buoyancy the model can be used to estimate the discharge properties at the base of the glacier.
    Description: We gratefully acknowledge technical assistance from Anders Jensen and thank anonymous reviewers for improving the clarity of the manuscript. CM thanks the Weston Howard Jr. Scholarship for funding. Support to CC was given by NSF project OCE-1434041 and OCE-1658079.
    Description: 2020-10-27
    Keywords: Ocean ; Glaciers ; Ice sheets ; Convection ; Laboratory/physical models
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  • 60
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(3), (2020): 679-694, doi:10.1175/JPO-D-19-0218.1.
    Description: The zonally integrated flow in a basin can be separated into the divergent/nondivergent parts, and a uniquely defined meridional overturning circulation (MOC) can be calculated. For a basin with significant volume exchange at zonal open boundaries, this method is competent in removing the components associated with the nonzero source terms due to zonal transports at open boundaries. This method was applied to the zonally integrated flow in the Indian Ocean basin extended all the way to the Antarctic by virtue of the ECCO dataset. The contributions due to two major zonal flow systems at open boundaries, the Indonesian Throughflow (ITF) and the Antarctic Circumpolar Current (ACC), were well separated from the rotational flow component, and a nondivergent overturning circulation pattern was identified. Comparisons with previous studies on the MOC of the Indian Ocean in different seasons showed overall consistency but with refinements in details to the south of the entry of the ITF, reflecting the influence of ITF on the MOC pattern in the domain. Other options of decomposition are also examined.
    Description: LH was supported by the National Basic Research Program of China through Grant 2019YFA0606703 and “The Fundamental Research Funds of Shandong University” (2019GN051). The authors thank the anonymous reviewers and the editor for their constructive comments. Code availability: The Matlab code that performs the decomposition and produces some figures in this paper is available at https://github.com/lei-han-SDU/IMOC/.
    Description: 2020-09-02
    Keywords: Meridional overturning circulation ; Ocean circulation ; Streamfunction
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  • 61
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Vallecillo-Viejo, I. C., Liscovitch-Brauer, N., Diaz Quiroz, J. F., Montiel-Gonzalez, Maria F., Nemes, Sonya E., Rangan, K. J., Levinson, S. R., Eisenberg, E., & Rosenthal, J. J. C. Spatially regulated editing of genetic information within a neuron. Nucleic Acids Research, (2020): gkaa172, doi: 10.1093/nar/gkaa172.
    Description: In eukaryotic cells, with the exception of the specialized genomes of mitochondria and plastids, all genetic information is sequestered within the nucleus. This arrangement imposes constraints on how the information can be tailored for different cellular regions, particularly in cells with complex morphologies like neurons. Although messenger RNAs (mRNAs), and the proteins that they encode, can be differentially sorted between cellular regions, the information itself does not change. RNA editing by adenosine deamination can alter the genome’s blueprint by recoding mRNAs; however, this process too is thought to be restricted to the nucleus. In this work, we show that ADAR2 (adenosine deaminase that acts on RNA), an RNA editing enzyme, is expressed outside of the nucleus in squid neurons. Furthermore, purified axoplasm exhibits adenosine-to-inosine activity and can specifically edit adenosines in a known substrate. Finally, a transcriptome-wide analysis of RNA editing reveals that tens of thousands of editing sites (〉70% of all sites) are edited more extensively in the squid giant axon than in its cell bodies. These results indicate that within a neuron RNA editing can recode genetic information in a region-specific manner.
    Description: National Science Foundation (NSF) [IOS1557748 to J.R.]; United States–Israel Binational Science Foundation [BSF2013094 to J.R. and E.E.]; The Grass Foundation grant in support of the Doryteuthis pealeii Genome Project, and a gift by Mr. Edward Owens. Funding for open access charge: United States–Israel Binational Science Foundation [BSF2013094].
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  • 62
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    American Meteorological Society
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(9), (2020): 2491-2506, doi:10.1175/JPO-D-20-0056.1.
    Description: An idealized two-layer shallow water model is applied to the study of the dynamics of the Arctic Ocean halocline. The model is forced by a surface stress distribution reflective of the observed wind stress pattern and ice motion and by an inflow representing the flow of Pacific Water through Bering Strait. The model reproduces the main elements of the halocline circulation: an anticyclonic Beaufort Gyre in the western basin (representing the Canada Basin), a cyclonic circulation in the eastern basin (representing the Eurasian Basin), and a Transpolar Drift between the two gyres directed from the upwind side of the basin to the downwind side of the basin. Analysis of the potential vorticity budget shows a basin-averaged balance primarily between potential vorticity input at the surface and dissipation at the lateral boundaries. However, advection is a leading-order term not only within the anticyclonic and cyclonic gyres but also between the gyres. This means that the eastern and western basins are dynamically connected through the advection of potential vorticity. Both eddy and mean fluxes play a role in connecting the regions of potential vorticity input at the surface with the opposite gyre and with the viscous boundary layers. These conclusions are based on a series of model runs in which forcing, topography, straits, and the Coriolis parameter were varied.
    Description: This study was supported by National Science Foundation Grant OPP-1822334. Comments and suggestions from two anonymous referees greatly helped to improve the paper.
    Description: 2021-02-17
    Keywords: Eddies ; Ekman pumping/transport ; Ocean circulation ; Ocean dynamics ; Potential vorticity ; Shallow-water equations
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  • 63
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 101(6), (2020): E897-E904, doi:10.1175/BAMS-D-19-0047.1.
    Description: Over the past 15 years, numerous studies have suggested that the sinking branches of Earth’s Hadley circulation and the associated subtropical dry zones have shifted poleward over the late twentieth century and early twenty-first century. Early estimates of this tropical widening from satellite observations and reanalyses varied from 0.25° to 3° latitude per decade, while estimates from global climate models show widening at the lower end of the observed range. In 2016, two working groups, the U.S. Climate Variability and Predictability (CLIVAR) working group on the Changing Width of the Tropical Belt and the International Space Science Institute (ISSI) Tropical Width Diagnostics Intercomparison Project, were formed to synthesize current understanding of the magnitude, causes, and impacts of the recent tropical widening evident in observations. These working groups concluded that the large rates of observed tropical widening noted by earlier studies resulted from their use of metrics that poorly capture changes in the Hadley circulation, or from the use of reanalyses that contained spurious trends. Accounting for these issues reduces the range of observed expansion rates to 0.25°–0.5° latitude decade‒1—within the range from model simulations. Models indicate that most of the recent Northern Hemisphere tropical widening is consistent with natural variability, whereas increasing greenhouse gases and decreasing stratospheric ozone likely played an important role in Southern Hemisphere widening. Whatever the cause or rate of expansion, understanding the regional impacts of tropical widening requires additional work, as different forcings can produce different regional patterns of widening.
    Description: We thank U.S. CLIVAR and ISSI for funding the two working groups. We thank all members of the working groups for helpful discussions, and the U.S. CLIVAR and ISSI offices and their sponsoring agencies (NASA, NOAA, NSF, DOE, ESA, Swiss Confederation, Swiss Academy of Sciences, and University of Bern) for supporting these groups and activities.
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  • 64
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(4), (2020): 887-905, doi:10.1175/JPO-D-19-0110.1.
    Description: The Equatorial Undercurrent (EUC) encounters the Galápagos Archipelago on the equator as it flows eastward across the Pacific. The impact of the Galápagos Archipelago on the EUC in the eastern equatorial Pacific remains largely unknown. In this study, the path of the EUC as it reaches the Galápagos Archipelago is measured directly using high-resolution observations obtained by autonomous underwater gliders. Gliders were deployed along three lines that define a closed region with the Galápagos Archipelago as the eastern boundary and 93°W from 2°S to 2°N as the western boundary. Twelve transects were simultaneously occupied along the three lines during 52 days in April–May 2016. Analysis of individual glider transects and average sections along each line show that the EUC splits around the Galápagos Archipelago. Velocity normal to the transects is used to estimate net horizontal volume transport into the volume. Downward integration of the net horizontal transport profile provides an estimate of the time- and areal-averaged vertical velocity profile over the 52-day time period. Local maxima in vertical velocity occur at depths of 25 and 280 m with magnitudes of (1.7 ± 0.6) × 10−5 m s−1 and (8.0 ± 1.6) × 10−5 m s−1, respectively. Volume transport as a function of salinity indicates that water crossing 93°W south (north) of 0.4°S tends to flow around the south (north) side of the Galápagos Archipelago. Comparisons are made between previous observational and modeling studies with differences attributed to effects of the strong 2015/16 El Niño event, the annual cycle of local winds, and varying longitudes between studies of the equatorial Pacific.
    Description: This work was supported by National Science Foundation (Grants OCE-1232971 and OCE-1233282) and the NASA Earth and Space Science Fellowship Program (Grant 80NSSC17K0443).
    Keywords: Tropics ; Boundary currents ; Topographic effects ; Transport ; Upwelling/downwelling ; In situ oceanic observations
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  • 65
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(10), (2020): 2849-2871, https://doi.org/10.1175/JPO-D-20-0086.1.
    Description: The structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 106 m3 s−1), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent recirculation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.
    Description: A.P., R.S.P., F.B., D.J.T., and A.L.R. were funded by Grants OCE-1259618 and OCE-1756361 from the National Science Foundation. I.L.B, F.S., and J.H. were supported by U.S. National Science Foundation Grants OCE-1258823 and OCE-1756272. Mooring data from MA2 was funded by the European Union 7th Framework Programme (FP7 2007-2013) under Grant 308299 (NACLIM) and the Horizon 2020 research and innovation program under Grant 727852 (Blue-Action). J.K. and M.O. acknowledge EU Horizon 2020 funding Grants 727852 (Blue-action) and 862626 (EuroSea) and from the German Ministry of Research and Education (RACE Program). G.W.K.M. acknowledges funding from the Natural Sciences and Engineering Research Council.
    Keywords: Boundary currents ; Convection ; Deep convection ; Transport ; In situ oceanic observations ; Seasonal cycle
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  • 66
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 101(11), (2020): E1996-E2004, https://doi.org/10.1175/BAMS-D-19-0305.1.
    Description: A long-standing challenge in oceanography is the observing, modeling, and prediction of vertical transport, which links the sunlit and atmospherically mediated surface boundary layer with the deeper ocean. Vertical motions play a critical role in the exchange of heat, freshwater, and biogeochemical tracers between the surface and the ocean interior. The most intense vertical velocities occur at horizontal scales less than 10 km, making them difficult to observe in the ocean and to resolve in models. Understanding how finescale turbulent motions and 0.1–10 km submesoscale processes contribute to the large-scale budgets of nutrients, oxygen, carbon, and heat and affect sea surface temperature, the air–sea exchange of gases, and the carbon cycle is one of the key challenges in oceanography.
    Description: CALYPSO is a Departmental Research Initiative (DRI) funded by the U.S. Office of Naval Research (ONR). It is a collaborative program involving more than 30 scientists and students and multiple institutions in the United States, Spain, and Italy. Measurements were conducted from the NRV Alliance, Pourquoi Pas?, and SOCIB. We are grateful to the captains and crews of these research vessels and the technical and scientific staff involved in making measurements, running models, analyzing data, and providing support.
    Description: 2021-05-01
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  • 67
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(4), (2020): 1045-1064, doi:10.1175/JPO-D-19-0137.1.
    Description: Three simulations of the circulation in the Gulf of Mexico (the “Gulf”) using different numerical general circulation models are compared with results of recent large-scale observational campaigns conducted throughout the deep (〉1500 m) Gulf. Analyses of these observations have provided new understanding of large-scale mean circulation features and variability throughout the deep Gulf. Important features include cyclonic flow along the continental slope, deep cyclonic circulation in the western Gulf, a counterrotating pair of cells under the Loop Current region, and a cyclonic cell to the south of this pair. These dominant circulation features are represented in each of the ocean model simulations, although with some obvious differences. A striking difference between all the models and the observations is that the simulated deep eddy kinetic energy under the Loop Current region is generally less than one-half of that computed from observations. A multidecadal integration of one of these numerical simulations is used to evaluate the uncertainty of estimates of velocity statistics in the deep Gulf computed from limited-length (4 years) observational or model records. This analysis shows that the main deep circulation features identified from the observational studies appear to be robust and are not substantially impacted by variability on time scales longer than the observational records. Differences in strengths and structures of the circulation features are identified, however, and quantified through standard error analysis of the statistical estimates using the model solutions.
    Description: This work was supported by the Gulf Research Program of the National Academy of Sciences under Awards 2000006422 and 2000009966. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Gulf Research Program or the National Academy of Sciences. The authors acknowledge the GLORYS project for providing the ocean reanalysis data used in the ROMS simulation. GLORYS is jointly conducted by MERCATOR OCEAN, CORIOLIS, and CNRS/INSU. Installation, recovery, data acquisition, and processing of the CANEK group current-meter moorings were possible because of CICESE-PetróleosMexicanos Grant PEP-CICESE 428229851 and the dedicated work of the crew of the B/O Justo Sierra and scientists of the CANEK group. The authors thank Dr. Aljaz Maslo, CICESE, for assistance with analysis of model data. The Bureau of Ocean Energy Management (BOEM), U.S. Dept. of the Interior, provided funding for the Lagrangian Study of the Deep Circulation in the Gulf of Mexico and the Observations and Dynamics of the Loop Current study. HYCOM simulation data are available from the HYCOM data server (https://www.hycom.org/data/goml0pt04/expt-02pt2), MITgcm data are available from the ECCO data server (http://ecco.ucsd.edu/gom_results2.html), and the ROMS simulation data are available from GRIIDC (NA.x837.000:0001).
    Keywords: Ocean circulation ; Abyssal circulation ; Bottom currents/bottom water ; Eddies ; Ocean models
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  • 68
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in da Fonseca, R. R., Couto, A., Machado, A. M., Brejova, B., Albertin, C. B., Silva, F., Gardner, P., Baril, T., Hayward, A., Campos, A., Ribeiro, A. M., Barrio-Hernandez, I., Hoving, H. J., Tafur-Jimenez, R., Chu, C., Frazao, B., Petersen, B., Penaloza, F., Musacchia, F., Alexander, G. C., Osorio, H., Winkelmann, I., Simakov, O., Rasmussen, S., Rahman, M. Z., Pisani, D., Vinther, J., Jarvis, E., Zhang, G., Strugnell, J. M., Castro, L. F. C., Fedrigo, O., Patricio, M., Li, Q., Rocha, S., Antunes, A., Wu, Y., Ma, B., Sanges, R., Vinar, T., Blagoev, B., Sicheritz-Ponten, T., Nielsen, R., & Gilbert, M. T. P. A draft genome sequence of the elusive giant squid, Architeuthis dux. Gigascience, 9(1), (2020): giz152. doi: 10.1093/gigascience/giz152.
    Description: Background: The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea–dwelling species will allow several pending evolutionary questions to be unlocked. Findings: We present a draft genome assembly that includes 200 Gb of Illumina reads, 4 Gb of Moleculo synthetic long reads, and 108 Gb of Chicago libraries, with a final size matching the estimated genome size of 2.7 Gb, and a scaffold N50 of 4.8 Mb. We also present an alternative assembly including 27 Gb raw reads generated using the Pacific Biosciences platform. In addition, we sequenced the proteome of the same individual and RNA from 3 different tissue types from 3 other species of squid (Onychoteuthis banksii, Dosidicus gigas, and Sthenoteuthis oualaniensis) to assist genome annotation. We annotated 33,406 protein-coding genes supported by evidence, and the genome completeness estimated by BUSCO reached 92%. Repetitive regions cover 49.17% of the genome. Conclusions: This annotated draft genome of A. dux provides a critical resource to investigate the unique traits of this species, including its gigantism and key adaptations to deep-sea environments.
    Description: R.R.F. thanks the Villum Fonden for grant VKR023446 (Villum Fonden Young Investigator Grant), the Portuguese Science Foundation (FCT) for grant PTDC/MAR/115347/2009; COMPETE-FCOMP-01-012; FEDER-015453, Marie Curie Actions (FP7-PEOPLE-2010-IEF, Proposal 272927), and the Danish National Research Foundation (DNRF96) for its funding of the Center for Macroecology, Evolution, and Climate. H.O. thanks the Rede Nacional de Espectrometria de Massa, ROTEIRO/0028/2013, ref. LISBOA-01-0145-FEDER-022125, supported by COMPETE and North Portugal Regional Operational Programme (Norte2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). A.C. thanks FCT for project UID/Multi/04423/2019. M.P. acknowledges the support from the Wellcome Trust (grant number WT108749/Z/15/Z) and the European Molecular Biology Laboratory. M.P.T.G. thanks the Danish National Research Foundation for its funding of the Center for GeoGenetics (grant DNRF94) and Lundbeck Foundation for grant R52–5062 on Pathogen Palaeogenomics. S.R. was supported by the Novo Nordisk Foundation grant NNF14CC0001. A.H. is supported by a Biotechnology and Biological Sciences Research Council David Phillips Fellowship (fellowship reference: BB/N020146/1). T.B. is supported by the Biotechnology and Biological Sciences Research Council-funded South West Biosciences Doctoral Training Partnership (training grant reference BB/M009122/1). This work was partially funded by the Lundbeck Foundation (R52-A4895 to B.B.). H.J.T.H. was supported by the David and Lucile Packard Foundation, the Netherlands Organization for Scientific Research (#825.09.016), and currently by the Deutsche Forschungsgemeinschaft (DFG) under grant HO 5569/2-1 (Emmy Noether Junior Research Group). T.V. and B. Brejova were supported by grants from the Slovak grant agency VEGA (1/0684/16, 1/0458/18). F.S. was supported by a PhD grant (SFRH/BD/126560/2016) from FCT. A.A. was partly supported by the FCT project PTDC/CTA-AMB/31774/2017. C.C. and Y.W. are partly supported by grant IIS-1526415 from the US National Science Foundation. Computation for the work described in this article was partially supported by the DeiC National Life Science Supercomputer at DTU.
    Keywords: Cephalopod ; Invertebrate ; Genome assembly
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  • 69
    Publication Date: 2022-10-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tassia, M. G., David, K. T., Townsend, J. P., & Halanych, K. M. TIAMMAt: leveraging biodiversity to revise protein domain models, evidence from innate immunity. Molecular Biology and Evolution, 38(12), (2021): 5806–5818, https://doi.org/10.1093/molbev/msab258.
    Description: Sequence annotation is fundamental for studying the evolution of protein families, particularly when working with nonmodel species. Given the rapid, ever-increasing number of species receiving high-quality genome sequencing, accurate domain modeling that is representative of species diversity is crucial for understanding protein family sequence evolution and their inferred function(s). Here, we describe a bioinformatic tool called Taxon-Informed Adjustment of Markov Model Attributes (TIAMMAt) which revises domain profile hidden Markov models (HMMs) by incorporating homologous domain sequences from underrepresented and nonmodel species. Using innate immunity pathways as a case study, we show that revising profile HMM parameters to directly account for variation in homologs among underrepresented species provides valuable insight into the evolution of protein families. Following adjustment by TIAMMAt, domain profile HMMs exhibit changes in their per-site amino acid state emission probabilities and insertion/deletion probabilities while maintaining the overall structure of the consensus sequence. Our results show that domain revision can heavily impact evolutionary interpretations for some families (i.e., NLR’s NACHT domain), whereas impact on other domains (e.g., rel homology domain and interferon regulatory factor domains) is minimal due to high levels of sequence conservation across the sampled phylogenetic depth (i.e., Metazoa). Importantly, TIAMMAt revises target domain models to reflect homologous sequence variation using the taxonomic distribution under consideration by the user. TIAMMAt’s flexibility to revise any subset of the Pfam database using a user-defined taxonomic pool will make it a valuable tool for future protein evolution studies, particularly when incorporating (or focusing) on nonmodel species.
    Description: This work was supported by The National Science Foundation (Grant No. IOS—1755377 to K.M.H., Rita Graze, and Elizabeth Hiltbold Schwartz), and K.T.D. was supported by The National Science Foundation’s Graduate Research Fellowship Program.
    Keywords: Protein evolution ; Domain annotation ; Animal evolution ; Innate immunity
    Repository Name: Woods Hole Open Access Server
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  • 70
    Publication Date: 2022-10-27
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Sherwood, C. R., van Dongeren, A., Doyle, J., Hegermiller, C. A., Hsu, T.-J., Kalra, T. S., Olabarrieta, M., Penko, A. M., Rafati, Y., Roelvink, D., van der Lugt, M., Veeramony, J., & Warner, J. C. Modeling the morphodynamics of coastal responses to extreme events: what shape are we in? Annual Review of Marine Science, 14, (2022): 457–492, https://doi.org/10.1146/annurev-marine-032221-090215.
    Description: This review focuses on recent advances in process-based numerical models of the impact of extreme storms on sandy coasts. Driven by larger-scale models of meteorology and hydrodynamics, these models simulate morphodynamics across the Sallenger storm-impact scale, including swash,collision, overwash, and inundation. Models are becoming both wider (as more processes are added) and deeper (as detailed physics replaces earlier parameterizations). Algorithms for wave-induced flows and sediment transport under shoaling waves are among the recent developments. Community and open-source models have become the norm. Observations of initial conditions (topography, land cover, and sediment characteristics) have become more detailed, and improvements in tropical cyclone and wave models provide forcing (winds, waves, surge, and upland flow) that is better resolved and more accurate, yielding commensurate improvements in model skill. We foresee that future storm-impact models will increasingly resolve individual waves, apply data assimilation, and be used in ensemble modeling modes to predict uncertainties.
    Description: All authors except D.R. were partially supported by the IFMSIP project, funded by US Office of Naval Research grant PE 0601153N under contracts N00014-17-1-2459 (Deltares), N00014-18-1-2785 (University of Delaware), N0001419WX00733 (US Naval Research Laboratory, Monterey), N0001418WX01447 (US Naval Research Laboratory, Stennis Space Center), and N0001418IP00016 (US Geological Survey). C.R.S., C.A.H., T.S.K., and J.C.W. were supported by the US Geological Survey Coastal/Marine Hazards and Resources Program. A.v.D. and M.v.d.L. were supported by the Deltares Strategic Research project Quantifying Flood Hazards and Impacts. M.O. acknowledges support from National Science Foundation project OCE-1554892.
    Keywords: Coastal morphodynamics ; Extreme storms ; Coastal modeling ; Sandy coasts ; Waves ; Sediment transport
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  • 71
    Publication Date: 2022-10-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shoshan, Y., Liscovitch-Brauer, N., Rosenthal, J. J. C., & Eisenberg, E. Adaptive proteome diversification by nonsynonymous A-to-I RNA editing in coleoid cephalopods. Molecular Biology and Evolution, 38(9), (2021): 3775–3788, https://doi.org/10.1093/molbev/msab154.
    Description: RNA editing by the ADAR enzymes converts selected adenosines into inosines, biological mimics for guanosines. By doing so, it alters protein-coding sequences, resulting in novel protein products that diversify the proteome beyond its genomic blueprint. Recoding is exceptionally abundant in the neural tissues of coleoid cephalopods (octopuses, squids, and cuttlefishes), with an over-representation of nonsynonymous edits suggesting positive selection. However, the extent to which proteome diversification by recoding provides an adaptive advantage is not known. It was recently suggested that the role of evolutionarily conserved edits is to compensate for harmful genomic substitutions, and that there is no added value in having an editable codon as compared with a restoration of the preferred genomic allele. Here, we show that this hypothesis fails to explain the evolutionary dynamics of recoding sites in coleoids. Instead, our results indicate that a large fraction of the shared, strongly recoded, sites in coleoids have been selected for proteome diversification, meaning that the fitness of an editable A is higher than an uneditable A or a genomically encoded G.
    Description: This research was supported by a grants from the United States–Israel Binational Science Foundation (BSF), Jerusalem, Israel (BSF2017262 to J.J.C.R. and E.E.), the Israel Science Foundation (3371/20 to E.E.) and the National Science Foundation (IOS 1827509 and 1557748 to J.J.C.R).
    Keywords: RNA editing ; Adaptation ; Evolution
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  • 72
    Publication Date: 2022-10-12
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(10), (2022): 2431-2444, https://doi.org/10.1175/jpo-d-22-0024.1.
    Description: A three-dimensional inertial model that conserves quasigeostrophic potential vorticity is proposed for wind-driven coastal upwelling along western boundaries. The dominant response to upwelling favorable winds is a surface-intensified baroclinic meridional boundary current with a subsurface countercurrent. The width of the current is not the baroclinic deformation radius but instead scales with the inertial boundary layer thickness while the depth scales as the ratio of the inertial boundary layer thickness to the baroclinic deformation radius. Thus, the boundary current scales depend on the stratification, wind stress, Coriolis parameter, and its meridional variation. In contrast to two-dimensional wind-driven coastal upwelling, the source waters that feed the Ekman upwelling are provided over the depth scale of this baroclinic current through a combination of onshore barotropic flow and from alongshore in the narrow boundary current. Topography forces an additional current whose characteristics depend on the topographic slope and width. For topography wider than the inertial boundary layer thickness the current is bottom intensified, while for narrow topography the current is wave-like in the vertical and trapped over the topography within the inertial boundary layer. An idealized primitive equation numerical model produces a similar baroclinic boundary current whose vertical length scale agrees with the theoretical scaling for both upwelling and downwelling favorable winds.
    Description: This research is supported in part by the China Scholarship Council (201906330102). H. G. is financially supported by the China Scholarship Council to study at WHOI for 2 years as a guest student. M.S. is supported by the National Science Foundation Grant OCE-1922538. Z. C. is supported by the ‘Taishan/Aoshan’ Talents program (2017ASTCPES05) the Fundamental Research Funds for the Central Universities (202072001).
    Description: 2023-03-30
    Keywords: Ekman pumping/transport ; Upwelling/downwelling ; Coastal flows
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  • 73
    Publication Date: 2022-10-12
    Description: Author Posting. © The Author(s), 2022. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Integrative & Comparative Biology 62(3), (2022): 805-816, https://doi.org/10.1093/icb/icac108.
    Description: Skates are a diverse group of dorso-ventrally compressed cartilaginous fish found primarily in high-latitude seas. These slow-growing oviparous fish deposit their fertilized eggs into cases, which then rest on the seafloor. Developing skates remain in their cases for 1–4 years after they are deposited, meaning the abiotic characteristics of the deposition sites, such as current and substrate type, must interact with the capsule in a way to promote long residency. Egg cases are morphologically variable and can be identified to species. Both the gross morphology and the microstructures of the egg case interact with substrate to determine how well a case stays in place on a current-swept seafloor. Our study investigated the egg case hydrodynamics of eight North Pacific skate species to understand how their morphology affects their ability to stay in place. We used a flume to measure maximum current velocity, or “break-away velocity,” each egg case could withstand before being swept off the substrate and a tilt table to measure the coefficient of static friction between each case and the substrate. We also used the programing software R to calculate theoretical drag on the egg cases of each species. For all flume trials, we found the morphology of egg cases and their orientation to flow to be significantly correlated with break-away velocity. In certain species, the morphology of the egg case was correlated with flow rate required to dislodge a case from the substrate in addition to the drag experienced in both the theoretical and flume experiments. These results effectively measure how well the egg cases of different species remain stationary in a similar habitat. Parsing out attachment biases and discrepancies in flow regimes of egg cases allows us to identify where we are likely to find other elusive species nursery sites. These results will aid predictive models for locating new nursery habitats and protective policies for avoiding the destruction of these nursery sites.
    Description: This work was supported by the NSF-REU and FHL Blinks-Beacon for funding JNE. And the Stephen and Ruth Wainwright Endowed Fellowship, BEACON and Hoag Awards, Robert T. Paine Experimental and Field Ecology Award, FHL Award, FHL Marine Science Fund, FHL Student Fund (Kohn), Patricia L. Dudley Endowment for funding KCH.
    Description: 2023-07-04
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  • 74
    Publication Date: 2022-10-12
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(10), (2022): 2325–2341, https://doi.org/10.1175/jpo-d-21-0015.1.
    Description: The ocean surface boundary layer is a gateway of energy transfer into the ocean. Wind-driven shear and meteorologically forced convection inject turbulent kinetic energy into the surface boundary layer, mixing the upper ocean and transforming its density structure. In the absence of direct observations or the capability to resolve subgrid-scale 3D turbulence in operational ocean models, the oceanography community relies on surface boundary layer similarity scalings (BLS) of shear and convective turbulence to represent this mixing. Despite their importance, near-surface mixing processes (and ubiquitous BLS representations of these processes) have been undersampled in high-energy forcing regimes such as the Southern Ocean. With the maturing of autonomous sampling platforms, there is now an opportunity to collect high-resolution spatial and temporal measurements in the full range of forcing conditions. Here, we characterize near-surface turbulence under strong wind forcing using the first long-duration glider microstructure survey of the Southern Ocean. We leverage these data to show that the measured turbulence is significantly higher than standard shear-convective BLS in the shallower parts of the surface boundary layer and lower than standard shear-convective BLS in the deeper parts of the surface boundary layer; the latter of which is not easily explained by present wave-effect literature. Consistent with the CBLAST (Coupled Boundary Layers and Air Sea Transfer) low winds experiment, this bias has the largest magnitude and spread in the shallowest 10% of the actively mixing layer under low-wind and breaking wave conditions, when relatively low levels of turbulent kinetic energy (TKE) in surface regime are easily biased by wave events.
    Description: This paper is VIMS Contribution 4103. Computational resources were provided by the VIMS Ocean-Atmosphere and Climate Change Research Fund. AUSSOM was supported by the OCE Division of the National Science Foundation (1558639).
    Keywords: Turbulence ; Wind shear ; Boundary layer ; Parameterization
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  • 75
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(1), (2021): 19-35, https://doi.org/10.1175/JPO-D-19-0233.1.
    Description: In the Beaufort Sea in September of 2015, concurrent mooring and microstructure observations were used to assess dissipation rates in the vicinity of 72°35′N, 145°1′W. Microstructure measurements from a free-falling profiler survey showed very low [O(10−10) W kg−1] turbulent kinetic energy dissipation rates ε. A finescale parameterization based on both shear and strain measurements was applied to estimate the ratio of shear to strain Rω and ε at the mooring location, and a strain-based parameterization was applied to the microstructure survey (which occurred approximately 100 km away from the mooring site) for direct comparison with microstructure results. The finescale parameterization worked well, with discrepancies ranging from a factor of 1–2.5 depending on depth. The largest discrepancies occurred at depths with high shear. Mean Rω was 17, and Rω showed high variability with values ranging from 3 to 50 over 8 days. Observed ε was slightly elevated (factor of 2–3 compared with a later survey of 11 profiles taken over 3 h) from 25 to 125 m following a wind event which occurred at the beginning of the mooring deployment, reaching a maximum of ε= 6 × 10−10 W kg−1 at 30-m depth. Velocity signals associated with near-inertial waves (NIWs) were observed at depths greater than 200 m, where the Atlantic Water mass represents a reservoir of oceanic heat. However, no evidence of elevated ε or heat fluxes was observed in association with NIWs at these depths in either the microstructure survey or the finescale parameterization estimates.
    Description: This work was supported by NSF Grants PLR 14-56705 and PLR-1303791 and by NSF Graduate Research Fellowship Grant DGE-1650112.
    Keywords: Ocean ; Arctic ; Internal waves ; Turbulence ; Diapycnal mixing
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  • 76
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(1),(2021): 3-17, https://doi.org/10.1175/JPO-D-20-0064.1.
    Description: The strong El Niño of 2014–16 was observed west of the Galápagos Islands through sustained deployment of underwater gliders. Three years of observations began in October 2013 and ended in October 2016, with observations at longitudes 93° and 95°W between latitudes 2°N and 2°S. In total, there were over 3000 glider-days of data, covering over 50 000 km with over 12 000 profiles. Coverage was superior closer to the Galápagos on 93°W, where gliders were equipped with sensors to measure velocity as well as temperature, salinity, and pressure. The repeated glider transects are analyzed to produce highly resolved mean sections and maps of observed variables as functions of time, latitude, and depth. The mean sections reveal the structure of the Equatorial Undercurrent (EUC), the South Equatorial Current, and the equatorial front. The mean fields are used to calculate potential vorticity Q and Richardson number Ri. Gradients in the mean are strong enough to make the sign of Q opposite to that of planetary vorticity and to have Ri near unity, suggestive of mixing. Temporal variability is dominated by the 2014–16 El Niño, with the arrival of depressed isopycnals documented in 2014 and 2015. Increases in eastward velocity advect anomalously salty water and are uncorrelated with warm temperatures and deep isopycnals. Thus, vertical advection is important to changes in heat, and horizontal advection is relevant to changes in salt. Implications of this work include possibilities for future research, model assessment and improvement, and sustained observations across the equatorial Pacific.
    Description: We gratefully acknowledge the support of the National Science Foundation (OCE-1232971, OCE-1233282) and the Ocean Observing and Monitoring Division of the National Oceanographic and Atmospheric Administration (NA13OAR4830216).
    Keywords: Ocean ; Tropics ; Currents ; El Nino ; In situ oceanic observations
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  • 77
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 38(1), (2021): 3-16, https://doi.org/10.1175/JTECH-D-20-0110.1.
    Description: Airborne expendable bathythermographs (AXBTs) are air-launched, single-use temperature–depth probes that telemeter temperature observations as VHF-modulated frequencies. This study describes the AXBT Real-Time Editing System (ARES), which is composed of two components: the ARES Data Acquisition System, which receives telemetered temperature–depth profiles with no external hardware other than a VHF radio receiver, and the ARES Profile Editing System, which quality controls AXBT temperature–depth profiles. The ARES Data Acquisition System performs fast Fourier transforms on windowed segments of the demodulated signal transmitted from the AXBT. For each segment, temperature is determined from peak frequency and depth from elapsed time since profile start. Valid signals are distinguished from noise by comparing peak signal levels and signal-to-noise ratios to predetermined thresholds. When evaluated using 387 profiles, the ARES Data Acquisition System produced temperature–depth profiles nearly identical to those generated using a Sippican MK-21 processor, while reducing the amount of noise from VHF interference included in those profiles. The ARES Profile Editor applies a series of automated checks to identify and correct common profile discrepancies before displaying the profile on an editing interface that provides simple user controls to make additional corrections. When evaluated against 1177 tropical Atlantic and Pacific AXBT profiles, the ARES automated quality control system successfully corrected 87% of the profiles without any required manual intervention. Necessary future work includes improvements to the automated quality control algorithm and algorithm evaluation against a broader dataset of temperature–depth profiles from around the world across all seasons.
    Description: This work was sponsored by the Office of Naval Research (Grants N000141812819 and N0001420WX00345) and the U.S. Navy’s Civilian Institution Office with the MIT–WHOI Joint Program.
    Keywords: Ocean ; In situ oceanic observations ; Profilers, oceanic
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  • 78
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 102(1), (2021): E99-E122, https://doi.org/10.1175/BAMS-D-19-0005.1.
    Description: The Red Sea, home to the second-longest coral reef system in the world, is a vital resource for the Kingdom of Saudi Arabia. The Red Sea provides 90% of the Kingdom’s potable water by desalinization, supporting tourism, shipping, aquaculture, and fishing industries, which together contribute about 10%–20% of the country’s GDP. All these activities, and those elsewhere in the Red Sea region, critically depend on oceanic and atmospheric conditions. At a time of mega-development projects along the Red Sea coast, and global warming, authorities are working on optimizing the harnessing of environmental resources, including renewable energy and rainwater harvesting. All these require high-resolution weather and climate information. Toward this end, we have undertaken a multipronged research and development activity in which we are developing an integrated data-driven regional coupled modeling system. The telescopically nested components include 5-km- to 600-m-resolution atmospheric models to address weather and climate challenges, 4-km- to 50-m-resolution ocean models with regional and coastal configurations to simulate and predict the general and mesoscale circulation, 4-km- to 100-m-resolution ecosystem models to simulate the biogeochemistry, and 1-km- to 50-m-resolution wave models. In addition, a complementary probabilistic transport modeling system predicts dispersion of contaminant plumes, oil spill, and marine ecosystem connectivity. Advanced ensemble data assimilation capabilities have also been implemented for accurate forecasting. Resulting achievements include significant advancement in our understanding of the regional circulation and its connection to the global climate, development, and validation of long-term Red Sea regional atmospheric–oceanic–wave reanalyses and forecasting capacities. These products are being extensively used by academia, government, and industry in various weather and marine studies and operations, environmental policies, renewable energy applications, impact assessment, flood forecasting, and more.
    Description: The development of the Red Sea modeling system is being supported by the Virtual Red Sea Initiative and the Competitive Research Grants (CRG) program from the Office of Sponsored Research at KAUST, Saudi Aramco Company through the Saudi ARAMCO Marine Environmental Center at KAUST, and by funds from KAEC, NEOM, and RSP through Beacon Development Company at KAUST.
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  • 79
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(11), (2020): 3267–3294, https://doi.org/10.1175/JPO-D-19-0310.1.
    Description: As part of the Flow Encountering Abrupt Topography (FLEAT) program, an array of pressure-sensor equipped inverted echo sounders (PIESs) was deployed north of Palau where the westward-flowing North Equatorial Current encounters the southern end of the Kyushu–Palau Ridge in the tropical North Pacific. Capitalizing on concurrent observations from satellite altimetry, FLEAT Spray gliders, and shipboard hydrography, the PIESs’ 10-month duration hourly bottom pressure p and round-trip acoustic travel time τ records are used to examine the magnitude and predictability of sea level and pycnocline depth changes and to track signal propagations through the array. Sea level and pycnocline depth are found to vary in response to a range of ocean processes, with their magnitude and predictability strongly process dependent. Signals characterized here comprise the barotropic tides, semidiurnal and diurnal internal tides, southeastward-propagating superinertial waves, westward-propagating mesoscale eddies, and a strong signature of sea level increase and pycnocline deepening associated with the region’s relaxation from El Niño to La Niña conditions. The presence of a broad band of superinertial waves just above the inertial frequency was unexpected and the FLEAT observations and output from a numerical model suggest that these waves detected near Palau are forced by remote winds east of the Philippines. The PIES-based estimates of pycnocline displacement are found to have large uncertainties relative to overall variability in pycnocline depth, as localized deep current variations arising from interactions of the large-scale currents with the abrupt topography around Palau have significant travel time variability.
    Description: Support for this research was provided by Office of Naval Research Grants N00014-16-1-2668, N00014-18-1-2406, N00014-15-1-2488, and N00014-15-1-2622. R.C.M. was additionally supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship.
    Keywords: Tropics ; Currents ; Eddies ; ENSO ; Internal waves ; Mesoscale processes
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  • 80
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    American Meteorological Society
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(11),(2020): 3331–3351, https://doi.org/10.1175/JPO-D-20-0035.1.
    Description: This study examines the generation of warm spiral structures (referred to as spiral streamers here) over Gulf Stream warm-core rings. Satellite sea surface temperature imagery shows spiral streamers forming after warmer water from the Gulf Stream or newly formed warm-core rings impinges onto old warm-core rings and then intrudes into the old rings. Field measurements in April 2018 capture the vertical structure of a warm spiral streamer as a shallow lens of low-density water winding over an old ring. Observations also show subduction on both sides of the spiral streamer, which carries surface waters downward. Idealized numerical model simulations initialized with observed water-mass densities reproduce spiral streamers over warm-core rings and reveal that their formation is a nonlinear submesoscale process forced by mesoscale dynamics. The negative density anomaly of the intruding water causes a density front at the interface between the intruding water and surface ring water, which, through thermal wind balance, drives a local anticyclonic flow. The pressure gradient and momentum advection of the local interfacial flow push the intruding water toward the ring center. The large-scale anticyclonic flow of the ring and the radial motion of the intruding water together form the spiral streamer. The observed subduction on both sides of the spiral streamer is part of the secondary cross-streamer circulation resulting from frontogenesis on the stretching streamer edges. The surface divergence of the secondary circulation pushes the side edges of the streamer away from each other, widens the warm spiral on the surface, and thus enhances its surface signal.
    Description: Authors W. G. Zhang and D. J. McGillicuddy are both supported by the National Science Foundation through Grant OCE 1657803.
    Keywords: Buoyancy ; Eddies ; Frontogenesis/frontolysis ; Mesoscale processes ; Transport ; Vertical motion
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  • 81
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(11), (2020): 3235–3251, https://doi.org/10.1175/JPO-D-20-0095.1.
    Description: The dense outflow through Denmark Strait is the largest contributor to the lower limb of the Atlantic meridional overturning circulation, yet a description of the full velocity field across the strait remains incomplete. Here we analyze a set of 22 shipboard hydrographic–velocity sections occupied along the Látrabjarg transect at the Denmark Strait sill, obtained over the time period 1993–2018. The sections provide the first complete view of the kinematic components at the sill: the shelfbreak East Greenland Current (EGC), the combined flow of the separated EGC, and the North Icelandic Jet (NIJ), and the northward-flowing North Icelandic Irminger Current (NIIC). The total mean transport of overflow water is 3.54 ± 0.29 Sv (1 Sv ≡ 106 m3 s−1), comparable to previous estimates. The dense overflow is partitioned in terms of water mass constituents and flow components. The mean transports of the two types of overflow water—Atlantic-origin Overflow Water and Arctic-origin Overflow Water—are comparable in Denmark Strait, while the merged NIJ–separated EGC transports 55% more water than the shelfbreak EGC. A significant degree of water mass exchange takes place between the branches as they converge in Denmark Strait. There are two dominant time-varying configurations of the flow that are characterized as a cyclonic state and a noncyclonic state. These appear to be wind-driven. A potential vorticity analysis indicates that the flow through Denmark Strait is subject to symmetric instability. This occurs at the top of the overflow layer, implying that the mixing/entrainment process that modifies the overflow water begins at the sill.
    Description: Funding for the study was provided by National Science Foundation (NSF) Grants OCE-1259618, OCE-1756361, and OCE-1558742. The German research cruises were financially supported through various EU Projects (e.g. THOR, NACLIM) and national projects (most recently TRR 181 “Energy Transfer in Atmosphere and Ocean” funded by the German Research Foundation and RACE II “Regional Atlantic Circulation and Global Change” funded by the German Federal Ministry for Education and Research). GWKM acknowledges the support of the Natural Sciences and Engineering Research Council of Canada. LP was supported by NSF Grant OCE-1657870.
    Keywords: Currents ; Instability ; Ocean circulation ; Ocean dynamics ; Potential vorticity
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  • 82
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 102(10), (2021): E1897–E1935, https://doi.org/10.1175/BAMS-D-19-0316.1.
    Description: Life on Earth vitally depends on the availability of water. Human pressure on freshwater resources is increasing, as is human exposure to weather-related extremes (droughts, storms, floods) caused by climate change. Understanding these changes is pivotal for developing mitigation and adaptation strategies. The Global Climate Observing System (GCOS) defines a suite of essential climate variables (ECVs), many related to the water cycle, required to systematically monitor Earth’s climate system. Since long-term observations of these ECVs are derived from different observation techniques, platforms, instruments, and retrieval algorithms, they often lack the accuracy, completeness, and resolution, to consistently characterize water cycle variability at multiple spatial and temporal scales. Here, we review the capability of ground-based and remotely sensed observations of water cycle ECVs to consistently observe the hydrological cycle. We evaluate the relevant land, atmosphere, and ocean water storages and the fluxes between them, including anthropogenic water use. Particularly, we assess how well they close on multiple temporal and spatial scales. On this basis, we discuss gaps in observation systems and formulate guidelines for future water cycle observation strategies. We conclude that, while long-term water cycle monitoring has greatly advanced in the past, many observational gaps still need to be overcome to close the water budget and enable a comprehensive and consistent assessment across scales. Trends in water cycle components can only be observed with great uncertainty, mainly due to insufficient length and homogeneity. An advanced closure of the water cycle requires improved model–data synthesis capabilities, particularly at regional to local scales.
    Description: WD acknowledges ESA’s QA4EO (ISMN) and CCI Soil Moisture projects. WD, CRV, AG, and KL acknowledge the G3P project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement 870353. MIH and MS acknowledge ESA’s CCI Water Vapour project. MS and RH acknowledges the support by the EUMETSAT member states through CM SAF. DGM acknowledges support from the European Research Council (ERC) under Grant Agreement 715254 (DRY–2–DRY). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).
    Description: 2022-04-01
    Keywords: Hydrologic cycle ; Satellite observations ; Surface fluxes ; Surface observations ; Water masses/storage ; Water budget/balance
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  • 83
    Publication Date: 2022-05-27
    Description: Author Posting. © Oxford University Press, 2021. This article is posted here by permission of [publisher] for personal use, not for redistribution. The definitive version was published in Lund, S., Acton, G., Clement, B., Okada, M., & Keigwin, L. On the relationship between palaeomagnetic secular variation and excursions-records from MIS 8-ODP leg 172. Geophysical Journal International, 225(2), (2021): 1129-1141, https://doi.org/10.1093/gji/ggaa564.
    Description: Palaeomagnetic secular variation (PSV) and excursion data obtained across MIS 8 (243–300 ka) from the western North Atlantic Ocean ODP (Ocean Drilling Program) sites 1060–1063 show composite high-resolution PSV records (both directions and relative palaeointensity) developed for each site and intercompared. Two methods of chronostratigraphy allow us to date these records. First, we used published results that compared the calcium carbonate records of ODP Leg 172 sediments and tuned them with Milankovich cyclicity. We also compared our palaeointensity records with the PISO-1500 global palaeointensity record that was dated with oxygen isotope stratigraphy. We prefer the PISO-1500 record to date our cores. Two excursions are preserved in our PSV records—Excursions 8α and 9α. Our revised age estimates for both excursions are 8α (236.7–239.8 ka) and 9α (283.7–286.9 ka). We have compared shipboard measurements of the two excursions with u-channel measurements of selected excursion intervals. Excursion 8α is interpreted as a ‘Class II’ excursion (local reversal) with in-phase inclination and declination changes; Excursion 9α is a ‘Class I’ excursion with 90° out-of-phase inclination and declination changes. Averaged directions (after removal of true excursional directions) and relative palaeointensity in 3 and 9 ka overlapping intervals show significant PSV directional variability over 104 yr timescales that is regionally correlatable among the four sites. A notable pattern of angular dispersion variability involves most time spent with low (∼10°) dispersion, with three shorter intervals of high (∼25°) dispersion. The relative palaeointensity variability also shows significant variability over 104 yr timescales with three notable intervals of low palaeointensity in all four records and a direct correspondence between the three low-palaeointensity intervals and the three intervals of high angular dispersion. The two magnetic field excursions occur in two of the three low-palaeointensity/high-dispersion intervals. This suggests that the geomagnetic field operates in two states between reversals, one with regular to high palaeointensity and low directional variability and one with low palaeointensity and significantly higher directional variability and excursions.
    Keywords: Geomagnetic excursions ; Palaeointensity ; Palaeomagnetic secular variation
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  • 84
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(2), (2021): 457–474, https://doi.org/10.1175/JPO-D-20-0088.1.
    Description: The meridional shift of the Kuroshio Extension (KE) front and changes in the formation of the North Pacific Subtropical Mode Water (STMW) during 1979–2018 are reported. The surface-to-subsurface structure of the KE front averaged over 142°–165°E has shifted poleward at a rate of ~0.23° ± 0.16° decade−1. The shift was caused mainly by the poleward shift of the downstream KE front (153°–165°E, ~0.41° ± 0.29° decade−1) and barely by the upstream KE front (142°–153°E). The long-term shift trend of the KE front showed two distinct behaviors before and after 2002. Before 2002, the surface KE front moved northward with a faster rate than the subsurface. After 2002, the surface KE front showed no obvious trend, but the subsurface KE front continued to move northward. The ventilation zone of the STMW, defined by the area between the 16° and 18°C isotherms or between the 25 and 25.5 kg m−3 isopycnals, contracted and displaced northward with a shoaling of the mixed layer depth hm before 2002 when the KE front moved northward. The STMW subduction rate was reduced by 0.76 Sv (63%; 1 Sv ≡ = 106 m3 s−1) during 1979–2018, most of which occurred before 2002. Of the three components affecting the total subduction rate, the temporal induction (−∂hm/∂t) was dominant accounting for 91% of the rate reduction, while the vertical pumping (−wmb) amounted to 8% and the lateral induction (−umb ⋅ ∇hm) was insignificant. The reduced temporal induction was attributed to both the contracted ventilation zone and the shallowed hm that were incurred by the poleward shift of KE front.
    Description: Xiaopei Lin is supported by the National Natural Science Foundation of China (41925025 and 92058203) and China’s national key research and development projects (2016YFA0601803). Baolan Wu is supported by the China Scholarship Council (201806330010). Lisan Yu thanks NOAA for support for her study on climate change and variability.
    Keywords: Boundary currents ; Decadal variability ; Fronts ; Water masses/storage
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  • 85
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(8),(2021): 2463–2482, https://doi.org/10.1175/JPO-D-20-0291.1.
    Description: This paper presents analyses of drifters with drogues at different depths—1, 10, 30, and 50 m—that were deployed in the Mediterranean Sea to investigate frontal subduction and upwelling. Drifter trajectories were used to estimate divergence, vorticity, vertical velocity, and finite-size Lyapunov exponents (FTLEs) and to investigate the balance of terms in the vorticity equation. The divergence and vorticity are O(f) and change sign along trajectories. Vertical velocity is O(1 mm s−1), increases with depth, indicates predominant upwelling with isolated downwelling events, and sometimes changes sign between 1 and 50 m. Vortex stretching is one of the significant terms, but not the only one, in the vorticity balance. Two-dimensional FTLEs are 2 × 10−5 s−1 after 1 day, 2 times as large as in a 400-m-resolution numerical model. Three-dimensional FTLEs are 50% larger than 2D FTLEs and are dominated by the vertical shear of horizontal velocity. Bootstrapping suggests uncertainty levels of ~10% of the time-mean absolute values for divergence and vorticity. Analysis of simulated drifters in a model suggests that drifter-based estimates of divergence and vorticity are close to the Eulerian model estimates, except when drifters get aligned into long filaments. Drifter-based vertical velocity is close to the Eulerian model estimates at 1 m but differs at deeper depths. The errors in the vertical velocity are largely due to the lateral separation between drifters at different depths and are partially due to only measuring at four depths. Overall, this paper demonstrates how drifters, heretofore restricted to 2D near-surface observations, can be used to learn about 3D flow properties throughout the upper layer of the water column.
    Description: Authors Rypina and Pratt were supported by U.S. Office of Naval Research (ONR) Grant N000141812417. Author Getscher acknowledges support from the U.S. Navy Civilian Institution Office with the MIT–WHOI Joint Program. Author Mourre acknowledges support from ONR Grant N00014-16-1-3130. We also thank Eugenio Cutolo for the initial technical support in the implementation of the ultra-high-resolution WMOP simulation. CALYPSO is a Departmental Research Initiative funded by the ONR.
    Description: 2022-01-16
    Keywords: Convergence/divergence ; Fronts ; Nonlinear dynamics ; Small scale processes ; Trajectories ; Upwelling/downwelling ; Vertical motion
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  • 86
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 102(10), (2021): E1936–E1951, https://doi.org/10.1175/BAMS-D-20-0113.1.
    Description: In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST 〉 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s−1). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s−1 wind and evaporation of 0.2 mm h−1. The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.
    Description: This work was supported through the U.S. Office of Naval Research’s Departmental Research Initiative: Monsoon Intraseasonal Oscillations in the Bay of Bengal, the Indian Ministry of Earth Science’s Ocean Mixing and Monsoons Program, and the Sri Lankan National Aquatic Resources Research and Development Agency. We thank the Captain and crew of the R/V Thompson for their help in data collection. Surface atmospheric fields included fluxes were quality controlled and processed by the Boundary Layer Observations and Processes Team within the NOAA Physical Sciences Laboratory. Forecast analysis was completed by India Meteorological Department. Drone image was taken by Shreyas Kamat with annotations by Gualtiero Spiro Jaeger. We also recognize the numerous researchers who supported cruise- and land-based measurements. This work represents Lamont-Doherty Earth Observatory contribution number 8503, and PMEL contribution number 5193.
    Description: 2022-04-01
    Keywords: Atmosphere-ocean interaction ; Monsoons ; In situ atmospheric observations ; In situ oceanic observations
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  • 87
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Suca, J. J., Wiley, D. N., Silva, T. L., Robuck, A. R., Richardson, D. E., Glancy, S. G., Clancey, E., Giandonato, T., Solow, A. R., Thompson, M. A., Hong, P., Baumann, H., Kaufman, L., & Llopiz, J. K. Sensitivity of sand lance to shifting prey and hydrography indicates forthcoming change to the northeast US shelf forage fish complex. Ices Journal of Marine Science, 78(3), (2021): 1023–1037, https://doi.org/10.1093/icesjms/fsaa251.
    Description: Northern sand lance (Ammodytes dubius) and Atlantic herring (Clupea harengus) represent the dominant lipid-rich forage fish species throughout the Northeast US shelf and are critical prey for numerous top predators. However, unlike Atlantic herring, there is little research on sand lance or information about drivers of their abundance. We use intra-annual measurements of sand lance diet, growth, and condition to explain annual variability in sand lance abundance on the Northeast US Shelf. Our observations indicate that northern sand lance feed, grow, and accumulate lipids in the late winter through summer, predominantly consuming the copepod Calanus finmarchicus. Sand lance then cease feeding, utilize lipids, and begin gonad development in the fall. We show that the abundance of C. finmarchicus influences sand lance parental condition and recruitment. Atlantic herring can mute this effect through intra-guild predation. Hydrography further impacts sand lance abundance as increases in warm slope water decrease overwinter survival of reproductive adults. The predicted changes to these drivers indicate that sand lance will no longer be able to fill the role of lipid-rich forage during times of low Atlantic herring abundance—changing the Northeast US shelf forage fish complex by the end of the century.
    Description: Research was funded by the Bureau of Ocean Energy Management (IA agreement M17PG0019; DNW, LK, HB, and JKL), including a subaward via the National Marine Sanctuary Foundation (18-11-B-203). Additional support came from the National Oceanic and Atmospheric Administration Woods Hole Sea Grant Program (NA18OAR4170104, Project No. R/O-57; JKL, HB, and DNW) and a National Science Foundation Long-term Ecological Research grant for the Northeast US Shelf Ecosystem (OCE 1655686; JKL). JJS was funded by the National Science Foundation Graduate Research Fellowship programme. ARR was funded by an NOAA Nancy Foster Scholarship.
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  • 88
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(1), (2021): 247-266, https://doi.org/10.1175/JPO-D-20-0098.1.
    Description: This study focuses on mechanisms of shelf valley bathymetry affecting the spread of riverine freshwater in the nearshore region. In the context of Changjiang River, a numerical model is used with different no-tide idealized configurations to simulate development of unforced river plumes over a sloping bottom, with and without a shelf valley off the estuary mouth. All simulated freshwater plumes are surface-trapped with continuously growing bulges near the estuary mouth and narrow coastal currents downstream. The simulations indicate that a shelf valley tends to compress the bulge along the direction of the valley long axis and modify the incident angle of the bulge flow impinging toward the coast, which then affects the strength of the coastal current. The bulge compression results from geostrophic adjustment and isobath-following tendency of the depth-averaged flow in the bulge region. Generally, the resulting change in the direction of the bulge impinging flow enhances down-shelf momentum advection and freshwater delivery into the coastal current. Sensitivity simulations with altered river discharges Q, Coriolis parameter, shelf bottom slope, valley geometry, and ambient stratification show that enhancement of down-shelf freshwater transport in the coastal current, ΔQc, increases with increasing valley depth within the bulge region and decreasing slope Burger number of the ambient shelf. Assuming potential vorticity conservation, a scaling formula of ΔQc/Q is developed, and it agrees well with results of the sensitivity simulations. Mechanisms of valley influences on unforced river plumes revealed here will help future studies of topographic influence on river plumes under more realistic conditions.
    Description: This work is conducted by Canbo Xiao and Weifeng (Gordon) Zhang during CX’s one-year visit at Woods Hole Oceanographic Institution (WHOI) in 2018–19. CX was supported by China Scholarship Council.
    Keywords: Continental shelf/slope ; Buoyancy ; Coastal flows ; Topographic effects ; Runoff ; Numerical analysis/modeling
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  • 89
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spingys, C. P., Garabato, A. C. N., Legg, S., Polzin, K. L., Abrahamsen, E. P., Buckingham, C. E., Forryan, A., & Frajka-Williams, E. E. Mixing and transformation in a deep western boundary current: a case study. Journal of Physical Oceanography, 51(4), (2021): 1205-1222, https://doi.org/10.1175/JPO-D-20-0132.1
    Description: Water-mass transformation by turbulent mixing is a key part of the deep-ocean overturning, as it drives the upwelling of dense waters formed at high latitudes. Here, we quantify this transformation and its underpinning processes in a small Southern Ocean basin: the Orkney Deep. Observations reveal a focusing of the transport in density space as a deep western boundary current (DWBC) flows through the region, associated with lightening and densification of the current’s denser and lighter layers, respectively. These transformations are driven by vigorous turbulent mixing. Comparing this transformation with measurements of the rate of turbulent kinetic energy dissipation indicates that, within the DWBC, turbulence operates with a high mixing efficiency, characterized by a dissipation ratio of 0.6 to 1 that exceeds the common value of 0.2. This result is corroborated by estimates of the dissipation ratio from microstructure observations. The causes of the transformation are unraveled through a decomposition into contributions dependent on the gradients in density space of the: dianeutral mixing rate, isoneutral area, and stratification. The transformation is found to be primarily driven by strong turbulence acting on an abrupt transition from the weakly stratified bottom boundary layer to well-stratified off-boundary waters. The reduced boundary layer stratification is generated by a downslope Ekman flow associated with the DWBC’s flow along sloping topography, and is further regulated by submesoscale instabilities acting to restratify near-boundary waters. Our results provide observational evidence endorsing the importance of near-boundary mixing processes to deep-ocean overturning, and highlight the role of DWBCs as hot spots of dianeutral upwelling.
    Description: CS, ACNG, AF, and EFW were supported by the U.K. Natural Environment Research Council (NERC) Grant NE/K013181/1. ACNG was supported by the Royal Society and Wolfson Foundation. EPA and CEB were supported by NERC Grant NE/K012843/1. CEB was funded by an MSCA grant (No. 798319) from the European Union’s Horizon 2020 program. EPA was supported by NERC Grant NE/N018095/1. SL and KP were supported by U.S. National Science Foundation Grants OCE-1536453 and OCE-1536779. SL acknowledges support of Award NA18OAR4320123 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the authors, and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, or the U.S. Department of Commerce.
    Keywords: Bottom currents ; Diapycnal mixing ; Turbulence ; Southern Ocean
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  • 90
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(3), (2021): 955–973, https://doi.org/10.1175/JPO-D-20-0240.1.
    Description: Fresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of freshwater enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much freshwater is mixed into the overturning circulation’s deep limb in the present day. To constrain these freshwater pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Freshwater sources are split into oceanic Polar Waters from the Arctic and surface freshwater fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv (1 Sv ≡ 106 m3 s−1) of the total 110 mSv of surface freshwater fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic freshwater outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.
    Description: We gratefully acknowledge the U.S. National Science Foundation: this work was supported by Grants OCE-1258823, OCE-1756272, OCE-1948335, and OCE-2038481. L.H.S. thanks the U.S. Norway Fulbright Foundation for the Norwegian Arctic Chair Grant 2019-20 that made the visit to Scripps Institution of Oceanography possible. N.P.H. acknowledges support by the U.K. Natural Environment Research Council (NERC) National Capability program CLASS (NE/R015953/1), and Grants U.K.-OSNAP (NE/K010875/1, NE/K010875/2) and U.K.-OSNAP Decade (NE/T00858X/1). We acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMIP6.
    Keywords: Arctic ; North Atlantic Ocean ; Conservation equations ; Meridional overturning circulation ; Ocean circulation ; Inverse methods
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  • 91
    Publication Date: 2022-05-27
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(7), (2021): 2087–2102, https://doi.org/10.1175/JPO-D-20-0255.1.
    Description: The boundary current system in the Labrador Sea plays an integral role in modulating convection in the interior basin. Four years of mooring data from the eastern Labrador Sea reveal persistent mesoscale variability in the West Greenland boundary current. Between 2014 and 2018, 197 middepth intensified cyclones were identified that passed the array near the 2000-m isobath. In this study, we quantify these features and show that they are the downstream manifestation of Denmark Strait Overflow Water (DSOW) cyclones. A composite cyclone is constructed revealing an average radius of 9 km, maximum azimuthal speed of 24 cm s−1, and a core propagation velocity of 27 cm s−1. The core propagation velocity is significantly smaller than upstream near Denmark Strait, allowing them to trap more water. The cyclones transport a 200-m-thick lens of dense water at the bottom of the water column and increase the transport of DSOW in the West Greenland boundary current by 17% relative to the background flow. Only a portion of the features generated at Denmark Strait make it to the Labrador Sea, implying that the remainder are shed into the interior Irminger Sea, are retroflected at Cape Farewell, or dissipate. A synoptic shipboard survey east of Cape Farewell, conducted in summer 2020, captured two of these features that shed further light on their structure and timing. This is the first time DSOW cyclones have been observed in the Labrador Sea—a discovery that could have important implications for interior stratification.
    Description: A. P. and R. S. P. were funded by National Science Foundation Grants OCE-1259618 and OCE-1756361. I. L. B. and F. S. were funded by National Science Foundation Grants OCE-1258823 and OCE-1756272. N. P. H. was supported by the Natural Environment Research Council U.K. OSNAP program (NE/K010875/1 and NE/K010700/1). M. A. S. was supported by NSF Grants OCE-1558742 and OPP-1822334.
    Description: 2021-12-08
    Keywords: Boundary currents ; Eddies ; Transport
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  • 92
    Publication Date: 2022-09-25
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(4), (2022): 597–616, https://doi.org/10.1175/jpo-d-21-0121.1.
    Description: We provide a first-principles analysis of the energy fluxes in the oceanic internal wave field. The resulting formula is remarkably similar to the renowned phenomenological formula for the turbulent dissipation rate in the ocean, which is known as the finescale parameterization. The prediction is based on the wave turbulence theory of internal gravity waves and on a new methodology devised for the computation of the associated energy fluxes. In the standard spectral representation of the wave energy density, in the two-dimensional vertical wavenumber–frequency (m–ω) domain, the energy fluxes associated with the steady state are found to be directed downscale in both coordinates, closely matching the finescale parameterization formula in functional form and in magnitude. These energy transfers are composed of a “local” and a “scale-separated” contributions; while the former is quantified numerically, the latter is dominated by the induced diffusion process and is amenable to analytical treatment. Contrary to previous results indicating an inverse energy cascade from high frequency to low, at odds with observations, our analysis of all nonzero coefficients of the diffusion tensor predicts a direct energy cascade. Moreover, by the same analysis fundamental spectra that had been deemed “no-flux” solutions are reinstated to the status of “constant-downscale-flux” solutions. This is consequential for an understanding of energy fluxes, sources, and sinks that fits in the observational paradigm of the finescale parameterization, solving at once two long-standing paradoxes that had earned the name of “oceanic ultraviolet catastrophe.”
    Description: The authors gratefully acknowledge support from the ONR Grant N00014-17-1-2852. YL gratefully acknowledges support from NSF DMS Award 2009418.
    Description: 2022-09-25
    Keywords: Ocean ; Gravity waves ; Nonlinear dynamics ; Ocean dynamics ; Mixing ; Fluxes ; Isopycnal coordinates ; Nonlinear models
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  • 93
    Publication Date: 2022-08-12
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 39(7), (2022): 1053–1083, https://doi.org/10.1175/jtech-d-21-0167.1.
    Description: The Ka-band Radar Interferometer (KaRIn) on the Surface Water and Ocean Topography (SWOT) satellite will revolutionize satellite altimetry by measuring sea surface height (SSH) with unprecedented accuracy and resolution across two 50-km swaths separated by a 20-km gap. The original plan to provide an SSH product with a footprint diameter of 1 km has changed to providing two SSH data products with footprint diameters of 0.5 and 2 km. The swath-averaged standard deviations and wavenumber spectra of the uncorrelated measurement errors for these footprints are derived from the SWOT science requirements that are expressed in terms of the wavenumber spectrum of SSH after smoothing with a filter cutoff wavelength of 15 km. The availability of two-dimensional fields of SSH within the measurement swaths will provide the first spaceborne estimates of instantaneous surface velocity and vorticity through the geostrophic equations. The swath-averaged standard deviations of the noise in estimates of velocity and vorticity derived by propagation of the uncorrelated SSH measurement noise through the finite difference approximations of the derivatives are shown to be too large for the SWOT data products to be used directly in most applications, even for the coarsest footprint diameter of 2 km. It is shown from wavenumber spectra and maps constructed from simulated SWOT data that additional smoothing will be required for most applications of SWOT estimates of velocity and vorticity. Equations are presented for the swath-averaged standard deviations and wavenumber spectra of residual noise in SSH and geostrophically computed velocity and vorticity after isotropic two-dimensional smoothing for any user-defined smoother and filter cutoff wavelength of the smoothing.
    Description: This research was supported by NASA Grant NNX16AH76G.
    Keywords: Sea level ; Altimetry ; Remote sensing ; Satellite observations ; Error analysis
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  • 94
    Publication Date: 2022-08-26
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2022. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: Defining the regional variability of minimum magnitude for earthquake detection is crucial for planning seismic networks. Knowing the earthquake detection magnitude values is fundamental for the optimal location of new stations and to select the priority for reactivating the stations of a seismic network in case of a breakdown. In general, the assessment of earthquake detection is performed by analysing seismic noise with spectral or more sophisticated methods. Further, to simulate amplitude values at the recording sites, spectral methods require knowledge of several geophysical parameters including rock density, S-wave velocity, corner frequency, quality factor, site specific decay parameter and so on, as well as a velocity model for the Earth's interior. The simulation results are generally expressed in terms of Mw and therefore a further conversion must be done to obtain the values of local magnitude (ML), which is the parameter commonly used for moderate and small earthquakes in seismic catalogues. Here, the relationship utilized by a seismic network to determine ML is directly applied to obtain the expected amplitude [in mm, as if it were recorded by a Wood–Anderson (WA) seismometer] at the recording site, without any additional assumptions. The station detection estimates are obtained by simply considering the ratio of the expected amplitude with respect to the background noise, also measured in mm. The seismic noise level for the station is estimated starting from four waveforms (each signal lasting 1 min) sampled at various times of the day for a period of one week. The proposed method is tested on Italian seismic events occurring in 2019 by using the locations of 16.879 earthquakes recorded by 374 stations. The first results indicate that by evaluating the station noise level with 5-s windows, a representative sample of the variability in expected noise level is generated for every station, even if only 4 min of signal per day over a week of recordings is used. The method was applied to define the detection level of the Italian National Seismic Network (RSN). The RSN detection level represents a reference for the definition and application of guidelines in the field of monitoring of subsurface industrial activities in Italy. The proposed approach can be successfully applied to define the current performance of a local seismic network (managed by private companies) and to estimate the expected further improvements, requested to fulfil the guidelines with the installation of new seismic stations. This method has been tested in Italy and can be reproduced wherever the local magnitude ML, based on synthetic WA records, is used.
    Description: Published
    Description: 1283–1297
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: Time-series analysis ; Earthquake ground motions ; Seismic noise ; Induced seismicity ; 04.06. Seismology ; 05.04. Instrumentation and techniques of general interest
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 95
    Publication Date: 2022-08-29
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(8), (2022): 1593-1611, https://doi.org/10.1175/jpo-d-21-0180.1.
    Description: This study presents novel observational estimates of turbulent dissipation and mixing in a standing meander between the Southeast Indian Ridge and the Macquarie Ridge in the Southern Ocean. By applying a finescale parameterization on the temperature, salinity, and velocity profiles collected from Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats in the upper 1600 m, we estimated the intensity and spatial distribution of dissipation rate and diapycnal mixing along the float tracks and investigated the sources. The indirect estimates indicate strong spatial and temporal variability of turbulent mixing varying from O(10−6) to O(10−3) m2 s−1 in the upper 1600 m. Elevated turbulent mixing is mostly associated with the Subantarctic Front (SAF) and mesoscale eddies. In the upper 500 m, enhanced mixing is associated with downward-propagating wind-generated near-inertial waves as well as the interaction between cyclonic eddies and upward-propagating internal waves. In the study region, the local topography does not play a role in turbulent mixing in the upper part of the water column, which has similar values in profiles over rough and smooth topography. However, both remotely generated internal tides and lee waves could contribute to the upward-propagating energy. Our results point strongly to the generation of turbulent mixing through the interaction of internal waves and the intense mesoscale eddy field.
    Description: The observations were funded through grants from the Australian Research Council Discovery Project (DP170102162) and Australia’s Marine National Facility. Surface drifters were provided by Dr. Shaun Dolk of the Global Drifter Program. AC was supported by an Australian Research Council Postdoctoral Fellowship. AC, HEP, and NLB acknowledge support from the Australian Government Department of the Environment and Energy National Environmental Science Program and the ARC Centre of Excellence in Climate Extremes. KP acknowledges the support from the National Science Foundation.
    Keywords: Diapycnal mixing ; Eddies ; Fronts ; Inertia-gravity waves ; Ocean dynamics
    Repository Name: Woods Hole Open Access Server
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  • 96
    Publication Date: 2022-08-19
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aoki, L. R., Brisbin, M. M., Hounshell, A. G., Kincaid, D. W., Larson, E., Sansom, B. J., Shogren, A. J., Smith, R. S., & Sullivan-Stack, J. Preparing aquatic research for an extreme future: call for improved definitions and responsive, multidisciplinary approaches. Bioscience, 72(6), (2022): 508-520, https://doi.org/10.1093/biosci/biac020.
    Description: Extreme events have increased in frequency globally, with a simultaneous surge in scientific interest about their ecological responses, particularly in sensitive freshwater, coastal, and marine ecosystems. We synthesized observational studies of extreme events in these aquatic ecosystems, finding that many studies do not use consistent definitions of extreme events. Furthermore, many studies do not capture ecological responses across the full spatial scale of the events. In contrast, sampling often extends across longer temporal scales than the event itself, highlighting the usefulness of long-term monitoring. Many ecological studies of extreme events measure biological responses but exclude chemical and physical responses, underscoring the need for integrative and multidisciplinary approaches. To advance extreme event research, we suggest prioritizing pre- and postevent data collection, including leveraging long-term monitoring; making intersite and cross-scale comparisons; adopting novel empirical and statistical approaches; and developing funding streams to support flexible and responsive data collection.
    Repository Name: Woods Hole Open Access Server
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  • 97
    Publication Date: 2022-08-25
    Description: Author Posting. © American Meteorological Society , 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Han, L., Seim, H., Bane, J., Todd, R. E., & Muglia, M. A shelf water cascading event near Cape Hatteras. Journal of Physical Oceanography, 51(6), (2021): 2021–2033, https://doi.org/10.1175/JPO-D-20-0156.1.
    Description: Carbon-rich Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB) shelf waters typically converge on the continental shelf near Cape Hatteras. Both are often exported to the adjacent open ocean in this region. During a survey of the region in mid-January 2018, there was no sign of shelf water export at the surface. Instead, a subsurface layer of shelf water with high chlorophyll and dissolved oxygen was observed at the edge of the Gulf Stream east of Cape Hatteras. Strong cooling over the MAB and SAB shelves in early January led to shelf waters being denser than offshore surface waters. Driven by the density gradient, the denser shelf waters cascaded beneath the Gulf Stream and were subsequently entrained into the Gulf Stream, as they were advected northeastward. Underwater glider observations 80 km downstream of the export location captured 0.44 Sv (1 Sv ≡ 106 m3 s−1) of shelf waters transported along the edge of the Gulf Stream in January 2018. In total, as much as 7 × 106 kg of carbon was exported from the continental shelf to a greater depth in the open ocean during this 5-day-long cascading event. Earlier observations of near-bottom temperature and salinity at a depth of 230 m captured several multiday episodes of shelf water at a location that was otherwise dominated by Gulf Stream water, indicating that the January 2018 cascading event was not unique. Cascading is an important, yet little-studied pathway of carbon export and sequestration at Cape Hatteras.
    Description: This research was funded by the National Science Foundation (Grants OCE-1558920 to University of North Carolina at Chapel Hill and OCE-1558521 to Woods Hole Oceanographic Institution) as part of PEACH. We acknowledge and thank Sara Haines for the processing and QC of the mooring data, and we thank the PEACH group for helpful discussions and for their support. Additional thanks are given to the crew of R/V Armstrong (AR-26).
    Keywords: Continental shelf/slope ; Fronts ; In situ oceanic observations
    Repository Name: Woods Hole Open Access Server
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  • 98
    Publication Date: 2022-07-13
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 39(2), (2022): 271–282. https://doi.org/10.1175/jtech-d-21-0069.1.
    Description: The inception of a moored buoy network in the northern Indian Ocean in 1997 paved the way for systematic collection of long-term time series observations of meteorological and oceanographic parameters. This buoy network was revamped in 2011 with Ocean Moored buoy Network for north Indian Ocean (OMNI) buoys fitted with additional sensors to better quantify the air–sea fluxes. An intercomparison of OMNI buoy measurements with the nearby Woods Hole Oceanographic Institution (WHOI) mooring during the year 2015 revealed an overestimation of downwelling longwave radiation (LWR↓). Analysis of the OMNI and WHOI radiation sensors at a test station at National Institute of Ocean Technology (NIOT) during 2019 revealed that the accurate and stable amplification of the thermopile voltage records along with the customized datalogger in the WHOI system results in better estimations of LWR↓. The offset in NIOT measured LWR↓ is estimated first by segregating the LWR↓ during clear-sky conditions identified using the downwelling shortwave radiation measurements from the same test station, and second, finding the offset by taking the difference with expected theoretical clear-sky LWR↓. The corrected LWR↓ exhibited good agreement with that of collocated WHOI measurements, with a correlation of 0.93. This method is applied to the OMNI field measurements and again compared with the nearby WHOI mooring measurements, exhibiting a better correlation of 0.95. This work has led to the revamping of radiation measurements in OMNI buoys and provides a reliable method to correct past measurements and improve estimation of air–sea fluxes in the Indian Ocean.
    Description: KJJ and RV thank Ministry of Earth Sciences (MoES), Government of India, Secretary, MoES, and Director, NIOT, for the support and encouragement in carrying out the work under the National Monsoon Mission, Ocean Mixing and Monsoon (OMM) program. AT, JTF, and RAW thank Office of Naval Research Grants N00014-19-12410 and N00014-17-12880, United States, for funding and support. The OOS team at NIOT is acknowledged for their efforts in maintaining the OMNI buoy network in North Indian Ocean. We acknowledge Dr. B.W. Blomquist, University of Colorado, for his support in computing clear-sky radiation and Iury T. Simoes-Sousa, University of Massachusetts, Dartmouth, for the graphics. NCMRWF, MoES, Government of India, is acknowledged for NGFS reanalysis dataset, which is produced under the collaboration between NCMRWF, IITM, and IMD.
    Keywords: Algorithms ; Buoy observations ; In situ oceanic observations ; Instrumentation/sensors ; Quality assurance/control
    Repository Name: Woods Hole Open Access Server
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  • 99
    Publication Date: 2022-09-14
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 35(2), (2022): 851–875, https://doi.org/10.1175/JCLI-D-20-0603.1.
    Description: The Earth system is accumulating energy due to human-induced activities. More than 90% of this energy has been stored in the ocean as heat since 1970, with ∼60% of that in the upper 700 m. Differences in upper-ocean heat content anomaly (OHCA) estimates, however, exist. Here, we use a dataset protocol for 1970–2008—with six instrumental bias adjustments applied to expendable bathythermograph (XBT) data, and mapped by six research groups—to evaluate the spatiotemporal spread in upper OHCA estimates arising from two choices: 1) those arising from instrumental bias adjustments and 2) those arising from mathematical (i.e., mapping) techniques to interpolate and extrapolate data in space and time. We also examined the effect of a common ocean mask, which reveals that exclusion of shallow seas can reduce global OHCA estimates up to 13%. Spread due to mapping method is largest in the Indian Ocean and in the eddy-rich and frontal regions of all basins. Spread due to XBT bias adjustment is largest in the Pacific Ocean within 30°N–30°S. In both mapping and XBT cases, spread is higher for 1990–2004. Statistically different trends among mapping methods are found not only in the poorly observed Southern Ocean but also in the well-observed northwest Atlantic. Our results cannot determine the best mapping or bias adjustment schemes, but they identify where important sensitivities exist, and thus where further understanding will help to refine OHCA estimates. These results highlight the need for further coordinated OHCA studies to evaluate the performance of existing mapping methods along with comprehensive assessment of uncertainty estimates.
    Description: AS is supported by a Tasmanian Graduate Research Scholarship, a CSIRO-UTAS Quantitative Marine Science top-up, and by the Australian Research Council (ARC) (CE170100023; DP160103130). CMD was partially supported by ARC (FT130101532) and the Natural Environmental Research Council (NE/P019293/1). RC was supported through funding from the Earth Systems and Climate Change Hub of the Australian Government’s National Environmental Science Program. TB is supported by the Climate Observation and Monitoring Program, National Oceanic and Atmosphere Administration, U.S. Department of commerce. GCJ and JML are supported by NOAA Research and the NOAA Ocean Climate Observation Program. This is PMEL contribution number 5065. JAC is supported by the Centre for Southern Hemisphere Oceans Research (CSHOR), jointly funded by the Qingdao National Laboratory for Marine Science and Technology (QNLM, China) and the Commonwealth Scientific and Industrial Research Organization (CSIRO, Australia) and Australian Research Council’s Discovery Project funding scheme (project DP190101173). The research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). Data used in this study are available on request.
    Keywords: Bias ; Interpolation schemes ; In situ oceanic observations ; Uncertainty ; Oceanic variability ; Trends
    Repository Name: Woods Hole Open Access Server
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  • 100
    Publication Date: 2022-09-15
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 39(2), (2022): 223–235, https://doi.org/10.1175/JTECH-D-21-0110.1.
    Description: Previous work with simulations of oceanographic high-frequency (HF) radars has identified possible improvements when using maximum likelihood estimation (MLE) for direction of arrival; however, methods for determining the number of emitters (here defined as spatially distinct patches of the ocean surface) have not realized these improvements. Here we describe and evaluate the use of the likelihood ratio (LR) for emitter detection, demonstrating its application to oceanographic HF radar data. The combined detection–estimation methods MLE-LR are compared with multiple signal classification method (MUSIC) and MUSIC parameters for SeaSonde HF radars, along with a method developed for 8-channel systems known as MUSIC-Highest. Results show that the use of MLE-LR produces similar accuracy, in terms of the RMS difference and correlation coefficients squared, as previous methods. We demonstrate that improved accuracy can be obtained for both methods, at the cost of fewer velocity observations and decreased spatial coverage. For SeaSondes, accuracy improvements are obtained with less commonly used parameter sets. The MLE-LR is shown to be able to resolve simultaneous closely spaced emitters, which has the potential to improve observations obtained by HF radars operating in complex current environments.
    Description: This work was supported by the National Science Foundation (NSF) under Grant OCE-1658475. Computing resources were provided by the UCSB Center for Scientific Computing through an NSF MRSEC (DMR-1720256) and NSF CNS-1725797.
    Keywords: Ocean ; Algorithms ; Data quality control ; Radars/radar observations ; Remote sensing ; Surface observations ; Quality assurance/control
    Repository Name: Woods Hole Open Access Server
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