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Millimeter wave spectroscopic measurements over the South Pole: 5. Morphology and evolution of HNO3vertical distribution, 1993 versus 1995 (2020)

McDonald, Michael ; de Zafra, Robert L ; Muscari, Giovanni

American Geophysical Union

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Publikationsdatum: 2020-09-21

Beschreibung: We compare differences and similarities in the annual stratospheric HNO3 cycle derived from ground‐based measurements at the South Pole during 1993 and 1995, after correcting an error in earlier published profile retrievals for 1993 which led to under estimation of mixing ratios. The data series presented here provide profiling over the range ∼16–48 km, and cover the fall‐winter‐spring cycle in the behavior of HNO3 in the extreme Antarctic with a large degree of temporal overlap. With the exception of one gap of 20 days, the combined data sets cover a full annual cycle. The record shows an increase in HNO3 above 30 km occurring about 20 days before sunset, which appears to be the result of higher altitude heterogeneous conversion of NOx as photolysis diminishes. Both years show a strong increase in HNO3 beginning about polar sunset, in a layer peaking at about 25 km, as additional NOx is heterogeneously converted to nitric acid. When temperatures drop to the polar stratospheric cloud (PSC) formation range near the end of May, gas phase HNO3 is rapidly reduced in the lower stratosphere, although at least 2–3 weeks of temperatures ≤192 K appear to be required to complete most of the gas‐phase removal at the upper end of the depletion range (22–25 km). Despite a significant difference in residual sulfate loading from the explosion of Mount Pinatubo, there appears to be little gross difference in the timing and effects of PSC formation in removing gas phase HNO3 in these 2 years, though removal may be more rapid in 1995. Incorporation of gas phase HNO3 into PSCs appears to be nearly complete up to ∼25 km by midwinter. We also see a repeat of the formation of gas phase HNO3 in the middle stratosphere in early midwinter of 1995 with about the same timing as in 1993, suggesting that this phenomenon is driven by a repetition of dynamical transport and appropriate temperatures and pressures in the polar night, and not (as has been suggested) by ion‐based heterogeneous chemistry that requires triggering by large relativistic electron fluxes. High‐altitude HNO3 production peaks during a period of ∼20 days, but appears to persist for up to ∼40 days in the 40–45 km range, ceasing well before sunrise. This HNO3 descends rapidly throughout the production period, at a rate in good agreement with theoretically determined midwinter subsidence rates. As noted in earlier studies, later warming of this region above PSC evaporation temperatures does not cause reappearance of large amounts of HNO3, indicating that most PSCs gravitationally sink out of the stratosphere before early spring. We present evidence that smaller PSCs do evaporate to ∼1 to 3.5 ppbv of HNO3 in the lower stratosphere, however, working downward from ∼25 km as temperatures rise during the late winter. There is a delay of ∼15 days after sunrise before photolysis causes significant depletion in the altitude range below ∼30 km, where subsidence has carried virtually all higher‐altitude HNO3 by polar sunrise. Some continued subsidence and photolysis combine to keep mixing ratios less than ∼5 ppbv below 30 km until the final breakdown of the vortex in November brings larger amounts of HNO3 with air from lower latitudes.

Beschreibung: Published

Beschreibung: 17739-17750

Beschreibung: 5A. Ricerche polari e paleoclima

Beschreibung: JCR Journal

Schlagwort(e): ozone depletion ; HNO3 ; Antarctic stratosphere ; 01.01. Atmosphere

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Retrospective short-term forecasting experiment in Italy based on the occurrence of strong (fore) shocks (2021)

Gasperini, Paolo ; Biondini, Emanuele ; Lolli, Barbara ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-03-15

Beschreibung: 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.

Beschreibung: 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.).

Beschreibung: Published

Beschreibung: 1192–1206

Beschreibung: 6T. Studi di pericolosità sismica e da maremoto

Beschreibung: JCR Journal

Schlagwort(e): Earthquake interaction ; Statistical seismology ; forecasting, ; prediction ; 04.06. Seismology

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Thermal structure of a vanishing subduction system. An example of seismically-derived crustal temperature along the Italian peninsula (2020)

Diaferia, Giovanni ; Cammarano, Fabio ; Faccenna, Claudio

Oxford University Press

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Publikationsdatum: 2020-10-16

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 239–247

Beschreibung: 1T. Struttura della Terra

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy (2020)

Passarelli, Luigi ; Hainzl, Sebastian ; Cesca, Simone ; [weitere]

Oxford University Press

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Publikationsdatum: 2020-12-15

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1553–1567

Beschreibung: 4T. Sismicità dell'Italia

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Non-stability of the noise HVSR at sites near or on topographic heights (2021)

La Rocca, Mario ; Chiappetta, Giuseppe Davide ; Gervasi, Anna ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-01-18

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 2162–2171

Beschreibung: 1T. Struttura della Terra

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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The Shallow Plumbing System of Piton de la Fournaise Volcano (La Reunion Island, Indian Ocean) Revealed by the Major 2007 Caldera-Forming Eruption (2021)

Di Muro, A. ; Metrich, N. ; Vergani, D ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-02-10

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1287-1315

Beschreibung: 2V. Struttura e sistema di alimentazione dei vulcani

Beschreibung: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici

Beschreibung: 4V. Processi pre-eruttivi

Beschreibung: 6A. Geochimica per l'ambiente e geologia medica

Beschreibung: JCR Journal

Schlagwort(e): Piton de la Fournaise ; plumbing system ; magma reservoir ; caldera collapse ; melt inclusions ; volatile budget ; isotope geochemistry ; basalt

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Numerical analysis of interseismic, coseismic and postseismic phases for normal and reverse faulting earthquakes in Italy (2021)

Albano, Matteo ; Barba, Salvatore ; Bignami, Christian ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-02-23

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 627–645

Beschreibung: 2T. Deformazione crostale attiva

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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An automatically generated high-resolution earthquake catalogue for the 2016–2017 Central Italy seismic sequence, including P and S phase arrival times (2021)

Spallarossa, Daniele ; Cattaneo, Marco ; Scafidi, Davide ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-03-24

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 555–571

Beschreibung: 3T. Fisica dei terremoti e Sorgente Sismica

Beschreibung: JCR Journal

Schlagwort(e): 04.06. Seismology

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Erratum: On seismic ambient noise cross-correlation and surface-wave attenuation (2021)

Boschi, Lapo ; Magrini, Fabrizio ; Cammarano, Fabio ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-05-12

Beschreibung: erratum paper

Beschreibung: Published

Beschreibung: 1090-1092

Beschreibung: 1T. Struttura della Terra

Beschreibung: JCR Journal

Schlagwort(e): Theoretical seismology ; Seismic attenuation ; Seismic noise ; Surface waves ; Free oscillations ; Seismic interferometry ; 04.06. Seismology ; 04.01. Earth Interior

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Crustal structure of the Azores Archipelago from Rayleigh wave ellipticity data (2021)

Berbellini, Andrea ; Frietsch, Michael ; Attanayake, Januka ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-05-12

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1232–1247

Beschreibung: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Changing modes and rates of mafic magma supply at Pantelleria (Sicily Channel, Southern Italy): new perspectives on the volcano factory drawn upon olivine records (2021)

Giuffrida, Marisa ; Nicotra, Eugenio ; Viccaro, Marco

Oxford University Press

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Publikationsdatum: 2021-05-12

Beschreibung: 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.

Beschreibung: Published

Beschreibung: egaa05

Beschreibung: 2V. Struttura e sistema di alimentazione dei vulcani

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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The Deep Plumbing System of Ischia: a Physico-chemical Window on the Fluid-saturated and CO2-sustained Neapolitan Volcanism (Southern Italy) (2021)

Moretti, Roberto ; Arienzo, Ilenia ; Orsi, Giovanni ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-05-12

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 951-984

Beschreibung: 2V. Struttura e sistema di alimentazione dei vulcani

Beschreibung: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici

Beschreibung: 4V. Processi pre-eruttivi

Beschreibung: 6A. Geochimica per l'ambiente e geologia medica

Beschreibung: JCR Journal

Schlagwort(e): CO2-fluxing ; melt inclusions ; redox state ; trachybasalts

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing (2021)

Gennaro, Mimma Emanuela ; Paonita, Antonio ; Iacono-Marziano, Giada ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-06-21

Beschreibung: 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.

Beschreibung: Published

Beschreibung: egaa095

Beschreibung: 4V. Processi pre-eruttivi

Beschreibung: JCR Journal

Schlagwort(e): melt inclusions ; sulphur solubility experiments ; XANES ; Mt. Etna ; 04.08. Volcanology

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Probabilistic Seismic Hazard Analysis at Regional and National Scales: State of the Art and Future Challenges (2020)

Gerstenberger, Matthew C. ; Marzocchi, Warner ; Allen, Trevor ; [weitere]

American Geophysical Union

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Publikationsdatum: 2020-09-01

Beschreibung: Seismic hazard modeling is a multidisciplinary science that aims to forecast earthquake occurrence and its resultant ground shaking. Such models consist of a probabilistic framework that quantifies uncertainty across a complex system; typically, this includes at least two model components developed from Earth science: seismic source and ground motion models. Although there is no scientific prescription for the forecast length, the most common probabilistic seismic hazard analyses consider forecasting windows of 30 to 50 years, which are typically an engineering demand for building code purposes. These types of analyses are the topic of this review paper. Although the core methods and assumptions of seismic hazard modeling have largely remained unchanged for more than 50 years, we review the most recent initiatives, which face the difficult task of meeting both the increasingly sophisticated demands of society and keeping pace with advances in scientific understanding. A need for more accurate and spatially precise hazard forecasting must be balanced with increased quantification of uncertainty and new challenges such as moving from time‐independent hazard to forecasts that are time dependent and specific to the time period of interest. Meeting these challenges requires the development of science‐driven models, which integrate all information available, the adoption of proper mathematical frameworks to quantify the different types of uncertainties in the hazard model, and the development of a proper testing phase of the model to quantify its consistency and skill. We review the state of the art of the National Seismic Hazard Modeling and how the most innovative approaches try to address future challenges.

Beschreibung: Published

Beschreibung: e2019RG000653

Beschreibung: 6T. Studi di pericolosità sismica e da maremoto

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Importance of earthquake rupture geometry on tsunami modelling: the Calabrian Arc subduction interface (Italy) case study (2020)

Tonini, Roberto ; Basili, Roberto ; Maesano, Francesco Emanuele ; [weitere]

Oxford University Press

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Publikationsdatum: 2020-10-16

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1805–1819

Beschreibung: 3T. Sorgente sismica

Beschreibung: 6T. Studi di pericolosità sismica e da maremoto

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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On the Heterogeneity of the Earthquake rupture (2021)

Malagnini, Luca ; Dreger, Douglas Scott ; Nadeau, Robert M ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-04-14

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1771–1781

Beschreibung: 2T. Deformazione crostale attiva

Beschreibung: JCR Journal

Schlagwort(e): Earthquake dynamics ; Earthquake source observations ; Dynamics and mechanics of faulting ; 04.06. Seismology

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Assessment of earthquake locations in 3D deterministic velocity models: a case study from the Altotiberina Near Fault Observatory (Italy) (2020)

Latorre, Diana ; Mirabella, Francesco ; Chiaraluce, Lauro ; [weitere]

American Geophysical Union

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Publikationsdatum: 2021-07-14

Beschreibung: An edited version of this paper was published by AGU. Copyright (2016) American Geophysical Union.

Beschreibung: The accuracy of earthquake locations and their correspondence with subsurface geology depends strongly on the accuracy of the available seismic velocity model. Most modern methods to construct a velocity model for earthquake location are based on the inversion of passive source seismological data. Another approach is the integration of high-resolution geological and geophysical data to construct deterministic velocity models in which earthquake locations can be directly correlated to the geological structures. Such models have to be kinematically consistent with independent seismological data in order to provide precise hypocenter solutions. We present the Altotiberina (AT) seismic model, a three-dimensional velocity model for the Upper Tiber Valley region (Northern Apennines, Italy), constructed by combining 300 km of seismic reflection profiles, 6 deep boreholes (down to 5 km depth), detailed data from geological surveys and direct measurements of P- and S-wave velocities performed in situ and in laboratory. We assess the robustness of the AT seismic model by locating 11,713 earthquakes with a non-linear, global-search inversion method and comparing the probabilistic hypocenter solutions to those calculated in three previously published velocity models, constructed by inverting passive seismological data only. Our results demonstrate that the AT seismic model is able to provide higher-quality hypocenter locations than the previous velocity models. Earthquake locations are consistent with the subsurface geological structures and show a high degree of spatial correlation with specific lithostratigraphic units, suggesting a lithological control on the seismic activity evolution.

Beschreibung: Published

Beschreibung: 8113-8135

Beschreibung: 4T. Sismicità dell'Italia

Beschreibung: JCR Journal

Schlagwort(e): deterministic velocity model ; earthquakes ; nonlinear hypocenter location ; lithological control on seismicity ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Intercomparison of stratospheric HNO3measurements over Antarctica: Ground-based millimeter-wave versus UARS/MLS Version 5 retrievals (2020)

Muscari, Giovanni ; Santee, Michelle l ; de Zafra, Robert L

American Geophysical Union

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Publikationsdatum: 2020-09-21

Beschreibung: [1] We present the first intercomparison between the two most comprehensive records of gas‐phase HNO3 profiles in the Antarctic stratosphere, covering the greater part of 1993 and 1995. We compare measurements by the Stony Brook Ground‐Based Millimeter‐wave Spectrometer (GBMS) at the South Pole with Version 5 HNO3 data from the Microwave Limb Sounder (MLS) aboard the Upper Atmospheric Research Satellite. Trajectory tracing was used to select MLS measurements in the 70°–80°S latitude band that sampled air observed by the GBMS during passage over the Pole. When temperatures were near the HNO3 condensation range, additional screening was performed to select MLS measurements that sampled air parcels within 1.5 K of the temperature they experienced over the Pole. Quantitative comparisons are given at 7 different potential temperature levels spanning the range ∼19–30 km. Agreement between the data sets is quite good between 465 and 655 K (∼20–25 km) during a large fraction of the year. Agreement is best during winter and spring, when seasonally averaged differences are generally within 1 ppbv below ∼25 km. At higher altitudes, and during summer and fall, the agreement becomes worse, and GBMS measurements can exceed MLS values by more than 3 ppbv. We provide evidence that differences occurring in the lower stratosphere during fall are due to lack of colocation between the two data sets during a period of strong poleward gradients in HNO3. Remaining discrepancies between GBMS and MLS V5 HNO3 measurements are thought to be due to instrumental or retrieval biases.

Beschreibung: Published

Beschreibung: id 4809

Beschreibung: 5A. Ricerche polari e paleoclima

Beschreibung: JCR Journal

Schlagwort(e): MLS ; Nitric acid ; polar stratosphere ; 01.01. Atmosphere

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Back to the future: old methods for new estimation and test of the Gutenberg–Richter b-value for catalogues with variable completeness (2020)

Taroni, Matteo

Oxford University Press

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Publikationsdatum: 2020-11-11

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 337–339

Beschreibung: 6T. Studi di pericolosità sismica e da maremoto

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Good practices in PSHA: declustering, b-value estimation, foreshocks and aftershocks inclusion; a case study in Italy (2020)

Taroni, Matteo ; Akinci, Aybige

Oxford University Press

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Publikationsdatum: 2020-12-21

Beschreibung: This article has been accepted for publication in Geophysical Journal International. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1174–1187

Beschreibung: 6T. Studi di pericolosità sismica e da maremoto

Beschreibung: JCR Journal

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Crustal and uppermost mantle shear wave velocity structure beneath the Middle East from surface wave tomography (2021)

Sandvol, Eric ; Tang, Zheng ; Lu, Yang ; [weitere]

Oxford University Press

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Publikationsdatum: 2021-05-12

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1349-1365

Beschreibung: 1T. Struttura della Terra

Beschreibung: JCR Journal

Schlagwort(e): 04.01. Earth Interior ; 04.06. Seismology

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Tropical Rains Controlling Deposition of Saharan Dust Across the North Atlantic Ocean (2020)

van der Does, Michèlle ; Brummer, Geert‐Jan A. ; van Crimpen, Fleur C. J. ; [weitere]

American Geophysical Union

In: EPIC3Geophysical Research Letters, American Geophysical Union, 47(5), ISSN: 0094-8276

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Publikationsdatum: 2020-05-13

Beschreibung: Mineral dust plays an important role in the atmospheric radiation budget as well as in the ocean carbon cycle through fertilization and by ballasting of settling organic matter. However, observational records of open‐ocean dust deposition are sparse. Here, we present the spatial and temporal evolution of Saharan dust deposition over 2 years from marine sediment traps across the North Atlantic, directly below the core of the Saharan dust plume, with highest dust fluxes observed in summer. We combined the observed deposition fluxes with model simulations and satellite observations and argue that dust deposition in the Atlantic is predominantly controlled by summer rains. The dominant depositional pathway changes from wet deposition in summer to dry deposition in winter. Wet deposition has previously been suggested to increase the release of dust‐derived nutrients and their bioavailability, which may be a key contributor to surface‐ocean productivity in remote and oligotrophic parts of the oceans.

Repository-Name: EPIC Alfred Wegener Institut

Materialart: Article , isiRev , info:eu-repo/semantics/article

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Arctic Continental Margin Sediments as Possible Fe and Mn Sources to Seawater as Sea Ice Retreats: Insights From the Eurasian Margin (2020)

Tessin, Allyson ; März, Christian ; Blais, Marie‐Amélie ; [weitere]

American Geophysical Union

In: EPIC3Global Biogeochemical Cycles, American Geophysical Union, 34(8), ISSN: 0886-6236

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Publikationsdatum: 2020-09-02

Repository-Name: EPIC Alfred Wegener Institut

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Ice flow and the conditions of the ice-bed interface at the onset of the Northeast Greenland Ice Stream (2020)

Franke, Steven ; Jansen, Daniela ; Beyer, Sebastian ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting 2020 - Online Everywhere, Online, 2020-12-01-2020-12-17American Geophysical Union

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Publikationsdatum: 2020-12-15

Beschreibung: The Northeast Greenland Ice Stream (NEGIS) is an important dynamic component contributing to the total mass balance of the Greenland ice sheet, as it reaches up to the central divide and drains 12% of the ice sheet. The ice stream geometry and surface velocities in the onset region of the NEGIS are not yet sufficiently well reproduced by ice sheet models. We present an assessment of the basal conditions of the onset region in a systematic analysis of airborne ultra-wideband radar data. Our data yield a new detailed model of ice-thickness distribution and basal topography in the upstream part of the ice stream. We observe a change from a smooth to a rougher bed where the ice stream widens from 10 to 60 km, and a distinct roughness anisotropy, indicating a preferred orientation of subglacial structures. The observation of off-nadir reflections that are symmetrical to the bed reflection in the radargrams suggests that these structures are elongated subglacial landforms, which in turn indicate potential streamlining of the bed. Together with basal water routing pathways, our observations hint to two different zones in this part of the NEGIS: an accelerating and smooth upstream region, which is collecting water, with reduced basal traction, and in the further downstream part, where the ice stream is slowing down and is widening, with a distribution of basal water towards the shear margins. Our findings support the hypothesis that the NEGIS is strongly interconnected to the subglacial water system in its onset region, but also to the subglacial substrate and morphology.

Repository-Name: EPIC Alfred Wegener Institut

Materialart: Conference , notRev

Format: application/pdf

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Simulated Thermohaline Fingerprints in Response to Different Greenland‐Scotland Ridge and Fram Strait Subsidence Histories (2020)

Hossain, Akil ; Knorr, Gregor ; Lohmann, Gerrit ; [weitere]

American Geophysical Union

In: EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union, 35, ISSN: 2572-4525

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Publikationsdatum: 2021-02-16

Beschreibung: Changes in ocean gateway configuration can induce basin‐scale rearrangements in ocean current characteristics. However, there is large uncertainty in the relative timing of the Oligocene/Miocene subsidence histories of the Greenland‐Scotland Ridge (GSR) and the Fram Strait (FS). By using a climate model, we investigate the temperature and salinity changes in response to the subsidence of these two key ocean gateways during early to middle Miocene. For a singular subsidence of the GSR, we detect warming and a salinity increase in the Nordic Seas and the Arctic Ocean. As convection sites shift to the north of Iceland, North Atlantic Deep Water (NADW) is formed at cooler temperatures. The associated deep ocean cooling and upwelling of deep waters to the Southern Ocean surface can cause a cooling in the southern high latitudes. These characteristic responses to the GSR deepening are independent of the FS being shallow or deep. An isolated subsidence of the FS gateway for a deep GSR shows less pronounced warming and salinity increase in the Nordic Seas. Arctic temperatures remain unaltered, but a stronger salinity increase is detected, which further increases the density of NADW. The increase in salinity enhances the contribution of NADW to the abyssal ocean at the expense of the colder southern source water component. These relative changes largely counteract each other and cause a negligible warming in the upwelling regions of the Southern Ocean.

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Planet Microbe: An Ontology-Enriched Cyberinfrastructure System for FAIR Marine ‘Omics Data (2020)

Blumberg, Kai ; Ponsero, Alise ; Bomhoff, Matthew D ; [weitere]

American Geophysical Union

In: EPIC3Ocean Sciences Meeting 2020, 2020-02-16-2020-02-21American Geophysical Union

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Publikationsdatum: 2020-02-12

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Antarctic Circumpolar Current Dynamics at the Pacific Entrance to the Drake Passage Over the Past 1.3 Million Years (2020)

Toyos, María H. ; Lamy, Frank ; Lange, Carina B. ; [weitere]

American Geophysical Union

In: EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union, 35(7), pp. e2019PA003773, ISSN: 2572-4525

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Publikationsdatum: 2021-02-01

Beschreibung: The Antarctic Circumpolar Current (ACC) is the world's largest current system connecting all three major basins of the global ocean. Our knowledge of glacial‐interglacial changes in ACC dynamics in the southeast Pacific is not well constrained and presently only based on reconstructions covering the last glacial cycle. Here we use a combination of mean sortable silt grain size of the terrigenous sediment fraction (10–63 μm, "Sortable Silt") and X‐ray fluorescence scanner‐derived Zr/Rb ratios as flow strength proxies to examine ACC variations at the Pacific entrance to the Drake Passage (DP) in the vicinity of the Subantarctic Front. Our results indicate that at the DP entrance, ACC strength varied by ~6–16% on glacial‐interglacial time scales, yielding higher current speeds during interglacial times and reduced current speeds during glacials. We provide evidence that previous observations of a reduction in DP throughflow during the last glacial period are part of a consistent pattern extending for at least the last 1.3 Ma. The orbital‐scale cyclicity follows well‐known global climate changes from prevailing ca. 41‐kyr cycles in the early part of the record (1.3 Ma to 850 ka; marine isotope stage 21) across the mid‐Pleistocene transition into the middle and late Pleistocene 100‐kyr world. A comparison to a bottom water flow record from the deep western boundary current off New Zealand (Ocean Drilling Program Site 1123) reveals anti‐phased changes between the two sites. The enhanced supply of deep water along the DP and into the Atlantic Ocean during interglacials corresponds to a weakened flow of the SW Pacific deep western boundary current.

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Scenario analysis can guide aquaculture planning to meet sustainable future production goals (2021)

Couture, Jessica L. ; Froehlich, Halley E. ; Buck, Bela H. ; [weitere]

Oxford University Press

In: EPIC3ICES Journal of Marine Science, Oxford University Press, pp. 1-11, ISSN: 1054-3139

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Publikationsdatum: 2021-07-23

Beschreibung: 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.

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Eruptive activity on the western flank of Piton de la Fournaise (La Réunion Island, Indian Ocean): insights on magma transfer, storage and evolution at an oceanic volcanic island (2020)

Boudoire, Guillaume ; Brugier, Yann-Aurélien ; Di Muro, Andréa ; [weitere]

Oxford University Press

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Publikationsdatum: 2020-06-17

Beschreibung: 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.

Beschreibung: Published

Beschreibung: 1717–1752

Beschreibung: 2V. Struttura e sistema di alimentazione dei vulcani

Beschreibung: JCR Journal

Schlagwort(e): transitional basalts ; clinopyroxene crystallization and resorption ; mantle–crust underplating

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

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Overview of the mating systems of Crustacea (2020)

Palaoro, Alexandre V. ; Beermann, Jan

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

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Publikationsdatum: 2021-02-24

Beschreibung: 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.

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Estimating Bioturbation From Replicated Small‐Sample Radiocarbon Ages (2021)

Dolman, Andrew M. ; Groeneveld, Jeroen ; Mollenhauer, Gesine ; [weitere]

American Geophysical Union

In: EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union, 36(7), ISSN: 2572-4517

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Publikationsdatum: 2021-09-20

Beschreibung: Marine sedimentary records are a key archive when reconstructing past climate; however, mixing at the seabed (bioturbation) can strongly influence climate records, especially when sedimentation rates are low. By commingling the climate signal from different time periods, bioturbation both smooths climate records, by damping fast climate variations, and creates noise when measurements are made on samples containing small numbers of individual proxy carriers, such as foraminifera. Bioturbation also influences radiocarbon-based age-depth models, as sample ages may not represent the true ages of the sediment layers from which they were picked. While these effects were first described several decades ago, the advent of ultra-small-sample $^{14}$C dating now allows samples containing very small numbers of foraminifera to be measured, thus enabling us to directly measure the age-heterogeneity of sediment for the first time. Here, we use radiocarbon dates measured on replicated samples of 3-30 foraminifera to estimate age-heterogeneity for five marine sediment cores with sedimentation rates ranging from 2-30 cm kyr$^{-1}$. From their age-heterogeneities and sedimentation rates we infer mixing depths of 10-20 cm for our core sites. Our results show that when accounting for age-heterogeneity, the true error of radiocarbon dating can be several times larger than the reported measurement. We present estimates of this uncertainty as a function of sedimentation rate and the number of individuals per radiocarbon date. A better understanding of this uncertainty will help us to optimise radiocarbon measurements, construct age models with appropriate uncertainties and better interpret marine paleo records.

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Methane Emissions from Northern Wetlands During the Holocene : A Synthesis Approach to Account for Wetland Expansion and Fen-Bog-Permafrost Transitions (Invited) (2021)

Treat, Claire ; Jones, Miriam C. ; Brosius, Laura ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting, New Orleans, LA, USA, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-23

Beschreibung: Methane emissions from northern high latitude wetlands constitute a major uncertainty in the atmospheric methane (CH4) budget during the Holocene. To reconstruct northern wetland methane emissions, we used an empirical model based on syntheses of observations of peat initiation from more than 3600 radiocarbon-dated basal peat ages, plant-macrofossil-derived peatland type from more than 250 peat cores from sites across the northern high latitudes, and observed CH4 emissions averaged from modern-day wetland types in order to explore the effects of wetland expansion and changes in wetland type. Peatland basal ages and plant macrofossil records showed the widespread formation of fens in major northern wetland complexes before 8000 BP. After 8000 BP, new fen formation continued, but widespread peatland succession (to bogs) and permafrost aggradation also occurred. Reconstructed CH4 emissions from peatlands increased rapidly between 10,600 BP and 6900 BP due to fen formation and expansion, then stabilized after 5000 BP at 42 ± 25 Tg CH4 y-1, as high methane-emitting fens transitioned to lower methane-emitting bogs and permafrost peatlands. Permafrost formation in northern peatlands after 1000 BP decreased CH4 emissions by 20% to 34 ± 21 Tg y-1 by the present day. Warming temperatures, changes in peatland hydrology, and permafrost thaw will likely change the magnitude of northern peatland emissions in the future.

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Monitoring the human footprint across the Arctic coastal region in the context of climate change impact assessment (2021)

Bartsch, Annett ; Pointner, Georg ; Widhalm, Barbara ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting 2021, Online, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-26

Beschreibung: Infrastructure and anthropogenic impacts are expanding across the Arctic. A consistent record of human impact is required in order to quantify the changes and to assess climate change impacts on the communities. We derived a first panarctic satellite-based record of expanding infrastructure and anthropogenic impacts along all permafrost affected coasts (100 km buffer) within the H2020 project Nunataryuk based on Sentinel-1/2 satellite imagery. C-band synthetic aperture radar and multi-spectral information is combined through a machine learning framework. Depending on region, we identified up to 50% more information (human presence) than in OpenStreetMap. The combination with satellite records on vegetation change (specifically NDVI from Landsat since 2000) allowed quantification of recent expansion of infrastructure. Most of the expanded human presence occurred in Russia related predominantly to oil/gas industry. The majority of areas with human presence will be subject to thaw by mid-21st century based on ground temperature trends derived from the ESA CCI+ Permafrost time series (1997-2019). Of specific concern in this context are also settlements located directly at permafrost affected coasts. An efficient erosion rate monitoring scheme needs to be developed and combined with settlement records in order to assess the risk for local communities and infrastructure. Relevant progress in the framework of the ESA EO4PAC project will be discussed.

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Evaluating a deep-learning approach for mapping retrogressive thaw slumps across the Arctic (2021)

Nitze, Ingmar ; Heidler, Konrad ; Barth, Sophia ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting 2021, Online, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-26

Beschreibung: Retrogressive thaw slumps (RTS) are typical landforms indicating processes of rapid thawing and degrading permafrost. Their abundance is increasing in many regions and quantifying their dynamics is of high importance for assessing geomorphic, hydrologic, and biogeochemical impacts of climate change in the Arctic. Here we present a deep-learning (DL) based semantic segmentation framework to detect RTS, using high-resolution multi-spectral PlanetScope, topographic (ArcticDEM elevation and slope), and medium-resolution multi-temporal Landsat Trend data. We created a highly automated processing pipeline, which is designed to allow reproducible results and to be flexible for multiple input data types. The processing workflow is based on the pytorch deep-learning framework and includes a variety of different segmentation architectures (UNet, UNet++, DeepLabV3), backbones and includes common data transformation techniques such as augmentation or normalization. We tested (training, validation) our DL based model in six different regions of 100 to 300 km² size across Canada, and Siberia. We performed a regional cross-validation (5 regions training, 1 region validation) to test the spatial robustness and transferability of the algorithm. Furthermore, we tested different architectures, backbones and loss-functions to identify the best performing and most robust parameter sets. For training the models we created a database of manually digitized and validated RTS polygons. The resulting model performance varied strongly between different regions with maximum Intersection over Union (IoU) scores between 0.15 and 0.58. The strong regional variation emphasizes the need for sufficiently large training data, which is representative of the diversity of RTS types. However, the creation of good training data proved to be challenging due to the fuzzy definition and delineation of RTS. We are further continuing to improve the usability and the functionality to add further datasets and classes. We will show first results from the upscaling beyond small test areas towards large spatial clusters of extensive RTS presence e.g. Peel Plateau in NW Canada.

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Evaluating the Effects of Tundra Fires on Soil Microtopography and Hydrologic Surface Networks in Polygonal Permafrost Landscapes (2021)

Rettelbach, Tabea ; Langer, Moritz ; Nitze, Ingmar ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting 2021, Online, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-26

Beschreibung: With the Earth’s climate rapidly warming, the Arctic represents one of the most vulnerable regions to environmental change. These northern high latitude regions experience intensified fire seasons and especially tundra fires are projected to become more frequent and severe. Fires in permafrost regions have extensive impacts, including the initiation of thermokarst (rapid thaw of ice-rich ground), as they combust the upper organic soil layers which provide insulation to the permafrost below. Rapid permafrost thaw is, thus, often observable in fire scars in the first years post-disturbance. In polygonal ice-wedge landscapes, this becomes most prevalent through melting ice wedges and degrading troughs. The further these ice wedges degrade, the more troughs will likely connect and build an extensive hydrological network with changing patterns and degrees of connectivity that influences hydrology and runoff. While subsiding troughs over melting ice wedges may host new ponds, an increasing connectivity may also subsequently lead to more drainage of ponds, which in turn can limit further thaw and help stabilize the landscape. To quantify the changes in such dynamic landscapes over large regions, highly automated methods are needed that allow extracting information on the geomorphic state and changes over time of ice-wedge trough networks from remote sensing data. We developed a computer vision algorithm to automatically derive ice-wedge polygonal networks and the current microtopography of the degrading troughs from very high resolution, airborne laserscanning-based digital terrain models. We represent the networks as graphs (a concept from the computer sciences to describe complex networks) and apply methods from graph theory to describe and quantify hydrological network characteristics of the changing landscape. In fire scars, we especially observe rapidly growing networks and fast micromorphological change in those degrading troughs. In our study, we provide a space-for-time substitution comparing fire scars throughout the Alaskan tundra of up to 70 years since the fire disturbance, to show how this type of disturbed landscape evolves over time.

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How to discover an unknown mega-landslide in the Siberian far-east (2021)

Nitze, Ingmar ; Tang, Hui ; Grosse, Guido

American Geophysical Union

In: EPIC3AGU Fall Meeting 2021, Online, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-26

Beschreibung: Using our custom visualization tool for multitemporal Landsat satellite imagery we discovered, to our knowledge, an undocumented mega-landslide in far-east Siberia, which occurred in summer 2017 (https://bit.ly/2WYRLM1; 61.55°N; 170.01°E). To create and visualize this unique dataset, we processed temporal trends of multispectral indices of 〉100,000 Landsat images for a period from 2000-2019 using the freely available Google Earth Engine cloud processing platform (https://ingmarnitze.users.earthengine.app/view/hotspottcvisapp). The megaslide has a size of 3.66 km² and using the ArcticDEM data we estimate a volume movement of ~20 Mm³. With this size and volume, the landslide is among the largest globally known in recent decades. The landslide is accompanied by a smaller one (0.31 km², 1 Mm³) about 600 m further east, which already occurred in summer 2015. The large landslide caused the formation of several small lakes by blocking two valleys with debris and within newly formed crevasses near the hilltop, which are still persisting as of August 2021. As this event occurred in a remote valley far from any settlement, no visible damage to infrastructure or human livelihoods was detected. The remoteness has likely led to being not detected, like many similar, albeit a lot smaller, erosion features in the Arctic permafrost region. In this presentation we will show the main properties of the landslide, potential trigger mechanisms in the traditional sense. As this region is located along the fringes of permafrost presence we will discuss its potential connection to the rapidly warming climate in the high latitudes. Further, we will discuss how such a large event remained undetected for several years. We discuss and highlight the value of our landscape change visualization tool based on Landsat trend analysis (see Nitze et al., AGU 2020), which helped us to identify this extreme event. With more and more available data sources, this tool in addition to automated image analysis (e.g. deep-learning) or seismic analysis will help to uncover the hidden processes and dynamics of the Earth’s surface.

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The future of community- and policy- relevant thermokarst research: Lessons learned and a call to action (2021)

Turetsky, Merritt R. ; Cox, William ; Dieleman, Catherine M . ; [weitere]

American Geophysical Union

In: EPIC3AGU Fall Meeting 2021, Online, 2021-12-13-2021-12-17American Geophysical Union

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Publikationsdatum: 2021-12-26

Beschreibung: Several decades of research have provided insight into patterns of and controls on thermokarst initiation and expansion, yet studies tend to focus on individual types of thermokarst (i.e., thaw lake formation and subsequent drainage) in particular regions. Today, we are left with uneven knowledge about abrupt permafrost thaw both conceptually and regionally. The goal of this presentation is to summarize recent advancements in monitoring thermokarst and its impact on soil, vegetation, and water while also framing a call to action for the next decade of research. Over the next decade, permafrost researchers must align their efforts on several fronts to not only increase our knowledge about changing permafrost but to align this knowledge with key community and policy needs. To support climate change planning and adaptation, northern communities need future thaw vulnerability mapped at scales relevant to their needs, which will require a suite of downscaled and new mapping and remote sensing products. Thermokarst predisposition maps based on circumpolar datasets greatly overestimate the area vulnerable to thermokarst, which can lead to poor planning and climate anxiety. In some situations, existing mapping products may be useful for downscaling with more detailed input data. In other situations, entirely new approaches may be required to support local action. A second key need for community relevant research is the ability to detect and monitor early warning indicators of thermokarst. Such information is needed to support scenario planning and to help mitigate the risks to social, cultural, and physical infrastructure created by permafrost change. We are evaluating the potential for using changes in vegetation, wetting/drying and topography as early warning indicators of thermokarst, all of which can be remotely sensed. Finally, integrating fine-scale disturbances such as thermokarst into large scale models remains a key challenge but critical for supporting sound climate policy. While a diversity of permafrost modeling approaches is necessary, we outline guiding principles that will help enhance model comparisons, assimilation of simulated data across spatiotemporal scales, and the ability for policy decisions to be rapidly informed by emerging science on permafrost change.

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The Surface Warming Attributable to Stratospheric Water Vapor in CO 2 ‐Caused Global Warming (2020)

Wang, Yuwei ; Huang, Yi

American Geophysical Union

In: Journal of Geophysical Research: Atmospheres. 2020; 125(17): Published 2020 Sep 03. doi: 10.1029/2020jd032752.

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Publikationsdatum: 2020-09-03

Print ISSN: 2169-897X

Digitale ISSN: 2169-8996

Thema: Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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New Insights Into Legacy Phosphorus From Fractionation of Streambed Sediment (2020)

Lannergård, Emma E. ; Agstam‐Norlin, Oskar ; Huser, Brian J. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Biogeosciences. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jg005763.

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Publikationsdatum: 2020-09-01

Print ISSN: 2169-8953

Digitale ISSN: 2169-8961

Thema: Geologie und Paläontologie , Biologie

Publiziert von American Geophysical Union

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Hydrometeor Size Sorting in the Asymmetric Eyewall of Hurricane Matthew (2016) (2020)

Laurencin, Chelsey N. ; Didlake, Anthony C. ; Loeffler, Scott D. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Atmospheres. 2020; 125(17): Published 2020 Sep 06. doi: 10.1029/2020jd032671.

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Publikationsdatum: 2020-09-06

Print ISSN: 2169-897X

Digitale ISSN: 2169-8996

Thema: Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Automatic Inversions of Strong‐Motion Records for Finite‐Fault Models of Significant Earthquakes in and Around Japan (2020)

Zheng, Xujun ; Zhang, Yong ; Wang, Rongjiang ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Solid Earth. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jb019992.

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Print ISSN: 2169-9313

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Thema: Geologie und Paläontologie , Physik

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On the Performance of Sentinel‐3 Altimetry Over New Reservoirs: Approaches to Determine Onboard A Priori Elevation (2020)

Zhang, Xingxing ; Jiang, Liguang ; Kittel, Cécile M. M. ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Aug 25. doi: 10.1029/2020gl088770.

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Publikationsdatum: 2020-08-25

Print ISSN: 0094-8276

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Thema: Geologie und Paläontologie , Physik

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Limited Regional Aerosol and Cloud Microphysical Changes Despite Unprecedented Decline in Nitrogen Oxide Pollution During the February 2020 COVID‐19 Shutdown in China (2020)

Diamond, Michael S. ; Wood, Robert

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Aug 25. doi: 10.1029/2020gl088913.

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Publikationsdatum: 2020-08-25

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Thema: Geologie und Paläontologie , Physik

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Making massive stars in the Galactic Centre via accretion on to low-mass stars within an accretion disc (2020)

Davies, Melvyn B ; Lin, Doug N C

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 498(3): 3452-3456. Published 2020 Aug 27. doi: 10.1093/mnras/staa2590.

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Beschreibung: The origin of the population of very massive stars observed within ∼0.4 pc of the supermassive black hole in the Galactic Centre is a mystery. Tidal forces from the black hole would likely inhibit in situ star formation whilst the youth of the massive stars would seem to exclude formation elsewhere followed by transportation (somehow) into the Galactic Centre. Here, we consider a third way to produce these massive stars from the lower mass stars contained in the nuclear stellar cluster which surrounds the supermassive black hole. A passing gas cloud can be tidally shredded by the supermassive black hole forming an accretion disc around the black hole. Stars embedded within this accretion disc will accrete gas from the disc via Bondi–Hoyle accretion, where the accretion rate on to a star, $dot{M}_star propto M_star ^2$. This super-exponential growth of accretion can lead to a steep increase in stellar masses, reaching the required 40–50 M⊙ in some cases. The mass growth rate depends sensitively on the stellar orbital eccentricities and their inclinations. The evolution of the orbital inclinations and/or their eccentricities as stars are trapped by the disc, and their orbits are circularized, will increase the number of massive stars produced. Thus accretion on to low-mass stars can lead to a top heavy stellar mass function in the Galactic Centre and other galactic nuclei. The massive stars produced will pollute the environment via supernova explosions and potentially produce compact binaries whose mergers may be detectable by the LIGO–VIRGO gravitational waves observatories.

Print ISSN: 0035-8711

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Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Effects of Temperature and Light on Methane Production of Widespread Marine Phytoplankton (2020)

Klintzsch, T. ; Langer, G. ; Wieland, A. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Biogeosciences. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jg005793.

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Thema: Geologie und Paläontologie , Biologie

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The observational impact of dust trapping in self-gravitating discs (2020)

Cadman, James ; Hall, Cassandra ; Rice, Ken ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 498(3): 4256-4271. Published 2020 Aug 27. doi: 10.1093/mnras/staa2596.

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Beschreibung: We present a 3D semi-analytical model of self-gravitating discs, and include a prescription for dust trapping in the disc spiral arms. Using Monte Carlo radiative transfer, we produce synthetic ALMA (Atacama Large Millimeter/submillimeter Array) observations of these discs. In doing so, we demonstrate that our model is capable of producing observational predictions, and able to model real image data of potentially self-gravitating discs. For a disc to generate spiral structure that would be observable with ALMA requires that the disc’s dust mass budget is dominated by millimetre- and centimetre-sized grains. Discs in which grains have grown to the grain fragmentation threshold may satisfy this criterion; thus, we predict that signatures of gravitational instability may be detectable in discs of lower mass than has previously been suggested. For example, we find that discs with disc-to-star mass ratios as low as 0.10 are capable of driving observable spiral arms. Substructure becomes challenging to detect in discs where no grain growth has occurred or in which grain growth has proceeded well beyond the grain fragmentation threshold. We demonstrate how we can use our model to retrieve information about dust trapping and grain growth through multiwavelength observations of discs, and using estimates of the opacity spectral index. Applying our disc model to the Elias 27, WaOph 6, and IM Lup systems, we find gravitational instability to be a plausible explanation for the observed substructure in all three discs, if sufficient grain growth has indeed occurred.

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Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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How Forest Degradation Affects Carbon and Water Cycles (2020)

Wheeling, Kate

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 25. doi: 10.1029/2020eo147133.

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Publikationsdatum: 2020-08-25

Beschreibung: Forest degradation may be as widespread as deforestation in the Amazon, but its impact on energy, carbon, and water fluxes is less well understood.

Print ISSN: 0096-3941

Digitale ISSN: 2324-9250

Thema: Geologie und Paläontologie

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Bringing Satellite Observations Down to Earth (2020)

Goss, Heather

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 25. doi: 10.1029/2020eo148281.

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Publikationsdatum: 2020-08-25

Beschreibung: This month’s issue of Eos shows how scientists can sometimes get a better look at something by stepping far—much, much farther—away.

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Thema: Geologie und Paläontologie

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A Broad Continuum of Aeolian Impact Ripple Morphologies on Mars is Enabled by Low Wind Dynamic Pressures (2020)

Sullivan, R. ; Kok, J. F. ; Katra, I. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Planets. 2020; 125(10): Published 2020 Oct 01. doi: 10.1029/2020je006485.

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Print ISSN: 2169-9097

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Thema: Geologie und Paläontologie , Physik

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Factories of CO-dark gas: molecular clouds with limited star formation efficiencies by far-ultraviolet feedback (2020)

Inoguchi, Mutsuko ; Hosokawa, Takashi ; Mineshige, Shin ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 497(4): 5061-5075. Published 2020 Aug 27. doi: 10.1093/mnras/staa2022.

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Beschreibung: The star formation in molecular clouds is inefficient. The ionizing extreme-ultraviolet radiation (hν ≥ 13.6 eV) from young clusters has been considered as a primary feedback effect to limit the star formation efficiency (SFE). Here, we focus on the effects of stellar far-ultraviolet (FUV) radiation (6 eV ≤ hν ≤ 13.6 eV) during the cloud disruption stage. The FUV radiation may further reduce the SFE via photoelectric heating, and it also affects the chemical states of the gas that is not converted to stars (‘cloud remnants’) via photodissociation of molecules. We have developed a one-dimensional semi-analytical model that follows the evolution of both the thermal and chemical structure of a photodissociation region (PDR) during the dynamical expansion of an H ii region. We investigate how the FUV feedback limits the SFE, supposing that the star formation is quenched in the PDR where the temperature is above a threshold value (e.g. 100 K). Our model predicts that the FUV feedback contributes to reduce the SFEs for massive (Mcl ≳ 105 M⊙) clouds with low surface densities ($Sigma _{ m cl}lesssim 100~{ m M}_odot , { m pc}^{-2}$). Moreover, we show that a large part of the H2 molecular gas contained in the cloud remnants should be ‘CO-dark’ under the FUV feedback for a wide range of cloud properties. Therefore, the dispersed molecular clouds are potential factories of CO-dark gas, which returns into the cycle of the interstellar medium.

Print ISSN: 0035-8711

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Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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PS1-STRM: Neural network source classification and photometric redshift catalogue for PS1 3π DR1 (2020)

Beck, Róbert ; Szapudi, István ; Flewelling, Heather ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; Published 2020 Aug 31. doi: 10.1093/mnras/staa2587. [early online release]

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Publikationsdatum: 2020-08-31

Beschreibung: The Pan-STARRS1 (PS1) 3π survey is a comprehensive optical imaging survey of three quarters of the sky in the grizy broad-band photometric filters. We present the methodology used in assembling the source classification and photometric redshift (photo-z) catalogue for PS1 3π Data Release 1, titled Pan-STARRS1 Source Types and Redshifts with Machine learning (PS1-STRM). For both main data products, we use neural network architectures, trained on a compilation of public spectroscopic measurements that has been cross-matched with PS1 sources. We quantify the parameter space coverage of our training data set, and flag extrapolation using self-organizing maps. We perform a Monte-Carlo sampling of the photometry to estimate photo-z uncertainty. The final catalogue contains 2,902,054,648 objects. On our validation data set, for non-extrapolated sources, we achieve an overall classification accuracy of $98.1\%$ for galaxies, $97.8\%$ for stars, and $96.6\%$ for quasars. Regarding the galaxy photo-z estimation, we attain an overall bias of =0.0005, a standard deviation of σ(Δznorm) = 0.0322, a median absolute deviation of MAD(Δznorm) = 0.0161, and an outlier fraction of $Pleft(|Delta z_{mathrm{norm}}|〉0.15 ight)=1.89\%$. The catalogue will be made available as a high-level science product via the Mikulski Archive for Space Telescopes.

Print ISSN: 0035-8711

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Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Measuring Basal Force Fluctuations of Debris Flows Using Seismic Recordings and Empirical Green's Functions (2020)

Allstadt, Kate E. ; Farin, Maxime ; Iverson, Richard M. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Earth Surface. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jf005590.

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Print ISSN: 2169-9003

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Thema: Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Gelatinous Zooplankton‐Mediated Carbon Flows in the Global Oceans: A Data‐Driven Modeling Study (2020)

Luo, Jessica Y. ; Condon, Robert H. ; Stock, Charles A. ; [weitere]

American Geophysical Union

In: Global Biogeochemical Cycles. 2020; 34(9): Published 2020 Sep 01. doi: 10.1029/2020gb006704.

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Publikationsdatum: 2020-09-01

Print ISSN: 0886-6236

Digitale ISSN: 1944-9224

Thema: Biologie , Chemie und Pharmazie , Geographie , Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Observations and Electron Density Retrievals of Jupiter's Discrete Auroral Arcs Using the Juno Microwave Radiometer (2020)

Hodges, Amorée ; Steffes, Paul ; Bellotti, Amadeo ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Planets. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2019je006293.

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Thema: Geologie und Paläontologie , Physik

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Storms Interact but Rarely Merge into Bigger Tempests (2020)

Kornei, Katherine

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 26. doi: 10.1029/2020eo148366.

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Publikationsdatum: 2020-08-26

Beschreibung: The Fujiwhara effect—complex interactions between large storms nearby each other—can steer hurricanes and tropical storms but doesn’t typically create colossal tempests.

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Thema: Geologie und Paläontologie

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Ideal Temperatures for Carbon Uptake by Subtropical Plants (2020)

Thompson, Elizabeth

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 26. doi: 10.1029/2020eo148250.

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Publikationsdatum: 2020-08-26

Beschreibung: Air temperatures in coastal ecosystems of Australia routinely exceed the optimum range for photosynthesis, hindering plants’ ability to take up atmospheric carbon.

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Thema: Geologie und Paläontologie

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Mathematical Insights into the West African Monsoon (2020)

Wheeling, Kate

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 26. doi: 10.1029/2020eo148254.

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Publikationsdatum: 2020-08-26

Beschreibung: A tool from dynamic systems theory is helping atmospheric scientists identify how dust and moisture mix over West Africa.

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Thema: Geologie und Paläontologie

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CO observations towards H i-rich Ultradiffuse Galaxies (2020)

Wang, Junzhi ; Yang, Kai ; Zhang, Zhi-Yu ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society / Letters. 2020; 499(1): L26-L30. Published 2020 Aug 27. doi: 10.1093/mnrasl/slaa150.

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Beschreibung: We present CO observations towards a sample of six H i-rich Ultradiffuse galaxies (UDGs) as well as one UDG (VLSB-A) in the Virgo Cluster with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope. CO J = 1–0 is marginally detected at 4σ level in AGC 122966, as the first detection of CO emission in UDGs. We estimate upper limits of molecular mass in other galaxies from the non-detection of CO lines. These upper limits and the marginal CO detection in AGC 122966 indicate low mass ratios between molecular and atomic gas masses. With the star formation efficiency derived from the molecular gas, we suggest that the inefficiency of star formation in such H i-rich UDGs is likely caused by the low efficiency in converting molecules from atomic gas, instead of low efficiency in forming stars from molecular gas.

Print ISSN: 1745-3925

Digitale ISSN: 1745-3933

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Height‐Integrated Ionospheric Conductances Parameterized By Interplanetary Magnetic Field and Substorm Phase (2020)

Carter, J. A. ; Milan, S. E. ; Paxton, L. J. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Space Physics. 2020; 125(10): Published 2020 Oct 01. doi: 10.1029/2020ja028121.

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Print ISSN: 2169-9380

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Thema: Geologie und Paläontologie , Physik

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Evolving Viscous Anisotropy in the Upper Mantle and Its Geodynamic Implications (2020)

Király, Á. ; Conrad, C. P. ; Hansen, L. N.

American Geophysical Union

In: Geochemistry, Geophysics, Geosystems. 2020; 21(10): Published 2020 Sep 25. doi: 10.1029/2020gc009159.

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Publikationsdatum: 2020-09-25

Digitale ISSN: 1525-2027

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Tidal Grounding‐Line Migration Modulated by Subglacial Hydrology (2020)

Warburton, K. L. P. ; Hewitt, D. R. ; Neufeld, J. A.

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 05. doi: 10.1029/2020gl089088.

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Publikationsdatum: 2020-09-05

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Thema: Geologie und Paläontologie , Physik

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Tidally Driven Interannual Variation in Extreme Sea Level Frequencies in the Gulf of Maine (2020)

Baranes, H. E. ; Woodruff, J. D. ; Talke, S. A. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Oceans. 2020; 125(10): Published 2020 Sep 29. doi: 10.1029/2020jc016291.

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Publikationsdatum: 2020-09-29

Print ISSN: 2169-9275

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Thema: Geologie und Paläontologie , Physik

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Electron Temperature Inversion by Stimulated Brillouin Scattering During Electron Gyroharmonic Heating at EISCAT (2020)

Fu, H. Y. ; Jiang, M. L. ; Wang, K. N. ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 05. doi: 10.1029/2020gl089747.

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Publikationsdatum: 2020-09-05

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Thema: Geologie und Paläontologie , Physik

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A 4‐Month Lead Predictor of Open‐Water Onset in Bering Strait (2020)

Luo, Xiaofan ; Wang, Yali ; Lu, Youyu ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 02. doi: 10.1029/2020gl089573.

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Publikationsdatum: 2020-09-02

Print ISSN: 0094-8276

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Thema: Geologie und Paläontologie , Physik

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Heterogeneity Affects Intertidal Flow Topology in Coastal Beach Aquifers (2020)

Geng, Xiaolong ; Michael, Holly A. ; Boufadel, Michel C. ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Aug 31. doi: 10.1029/2020gl089612.

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Thema: Geologie und Paläontologie , Physik

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Evidence for Fluid Migration During the 2016 Meinong, Taiwan, Aftershock Sequence (2020)

Hsu, Y.‐F. ; Huang, H.‐H. ; Huang, M.‐H. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Solid Earth. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jb019994.

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Print ISSN: 2169-9313

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Thema: Geologie und Paläontologie , Physik

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Temporal and Vertical Oxygen Gradients Modulate Nitrous Oxide Production in a Seasonally Anoxic Fjord: Saanich Inlet, British Columbia (2020)

Ji, Qixing ; Jameson, Brett D. ; Juniper, S. Kim ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Biogeosciences. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jg005631.

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Print ISSN: 2169-8953

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Thema: Geologie und Paläontologie , Biologie

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Toward Source Region Tomography With Intersource Interferometry: Shear Wave Velocity From 2018 West Bohemia Swarm Earthquakes (2020)

Eulenfeld, Tom

American Geophysical Union

In: Journal of Geophysical Research: Solid Earth. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020jb019931.

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Publikationsdatum: 2020-09-01

Print ISSN: 2169-9313

Digitale ISSN: 2169-9356

Thema: Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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This Week: Hurricanes, Space Weather, and Marvelous Microbes (2020)

,

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 28. doi: 10.1029/2020eo148380.

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Beschreibung: What Earth and space science stories are we recommending this week?

Print ISSN: 0096-3941

Digitale ISSN: 2324-9250

Thema: Geologie und Paläontologie

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The Challenges of Fieldwork for LGBTQ+ Geoscientists (2020)

Olcott, Alison ; Downen, Matthew

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 28. doi: 10.1029/2020eo148200.

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Beschreibung: A new survey reveals the unique issues that traveling for research poses for LGBTQ+ scientists. The data should help us create solutions that foster safety and inclusion.

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Digitale ISSN: 2324-9250

Thema: Geologie und Paläontologie

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Small Impact Crater Populations on Saturn's Moon Tethys and Implications for Source Impactors in the System (2020)

Ferguson, S. N. ; Rhoden, A. R. ; Kirchoff, M. R.

American Geophysical Union

In: Journal of Geophysical Research: Planets. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2020je006400.

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Print ISSN: 2169-9097

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Thema: Geologie und Paläontologie , Physik

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Far‐Ranging Impact of Mountain Waves Excited Over Greenland on Stratospheric Dehydration and Rehydration (2020)

Kivi, Rigel ; Dörnbrack, Andreas ; Sprenger, Michael ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Atmospheres. 2020; 125(18): Published 2020 Sep 18. doi: 10.1029/2020jd033055.

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Publikationsdatum: 2020-09-18

Print ISSN: 2169-897X

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Thema: Geologie und Paläontologie , Physik

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Assessing Shifts in Regional Hydroclimatic Conditions of U.S. River Basins in Response to Climate Change over the 21st Century (2020)

Heidari, Hadi ; Arabi, Mazdak ; Warziniack, Travis ; [weitere]

American Geophysical Union

In: Earth's Future. 2020; 8(10): Published 2020 Oct 01. doi: 10.1029/2020ef001657.

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Publikationsdatum: 2020-10-01

Digitale ISSN: 2328-4277

Thema: Geologie und Paläontologie

Publiziert von American Geophysical Union

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The Wicked Problem of Diffuse Nutrient Pollution from Agriculture (2020)

Sharma, Annabel

Oxford University Press

In: Journal of Environmental Law. 2020; Published 2020 Oct 09. doi: 10.1093/jel/eqaa017. [early online release]

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Publikationsdatum: 2020-10-09

Beschreibung: Diffuse nutrient pollution from agriculture has been the concern of policymakers for several decades, and yet it remains a persistent environmental issue. The current approach to mitigating the problem is predominantly via command and control regulation within the Nitrates Directive and the Water Framework Directive. This article will set out how diffuse pollution can be considered a wicked policy problem which acts as an explanation of how it has eluded the current regulatory regime. It will further establish that the traditional planning process overlooked the complexity of the problem. Finally, it will illustrate the ineffectiveness of the current regulatory framework to mitigate the problem. This will be exemplified through the legal framework of Northern Ireland.

Print ISSN: 0952-8873

Digitale ISSN: 1464-374X

Thema: Energietechnik , Rechtswissenschaft

Publiziert von Oxford University Press

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Paleomagnetism of the Middle Cenozoic Mula Basin (East Tibet): Evidence for km‐Scale Crustal Blocks Rotated by Midlower Crust Drag (2020)

Todrani, Alessandro ; Zhang, Bo ; Speranza, Fabio ; [weitere]

American Geophysical Union

In: Geochemistry, Geophysics, Geosystems. 2020; 21(9): Published 2020 Aug 27. doi: 10.1029/2020gc009225.

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Publikationsdatum: 2020-08-27

Digitale ISSN: 1525-2027

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Errors From Asymmetric Emission Rate in Spaceborne, Limb Sounding Doppler Interferometry: A Correction Algorithm With Application to ICON/MIGHTI (2020)

Wu, Yen‐Jung J. ; Harding, Brian J. ; Triplett, Colin C. ; [weitere]

American Geophysical Union

In: Earth and Space Science. 2020; 7(10): Published 2020 Oct 01. doi: 10.1029/2020ea001164.

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Digitale ISSN: 2333-5084

Thema: Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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High‐Resolution Mg/Ca and δ 18 O Patterns in Modern Neogloboquadrina pachyderma From the Fram Strait and Irminger Sea (2020)

Livsey, Caitlin M. ; Kozdon, Reinhard ; Bauch, Dorothea ; [weitere]

American Geophysical Union

In: Paleoceanography and Paleoclimatology. 2020; 35(9): Published 2020 Sep 01. doi: 10.1029/2020pa003969.

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Print ISSN: 2572-4517

Digitale ISSN: 2572-4525

Thema: Geologie und Paläontologie

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Balloons in the Earth's Auroral Science—BALBOA's Modern Exploration (2020)

Zhou, X.‐Y. ; Rafol, S. B. ; Michell, R. G. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Space Physics. 2020; 125(10): Published 2020 Oct 01. doi: 10.1029/2019ja027603.

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Print ISSN: 2169-9380

Digitale ISSN: 2169-9402

Thema: Geologie und Paläontologie , Physik

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Some Differences in the Dynamics of the Intermediate Descending Layers Observed During Periods of Maximum and Minimum Solar Flux (2020)

Santos, A. M. ; Batista, I. S. ; Sobral, J. H. A. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Space Physics. 2020; 125(10): Published 2020 Sep 30. doi: 10.1029/2019ja027682.

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Publikationsdatum: 2020-09-30

Print ISSN: 2169-9380

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Thema: Geologie und Paläontologie , Physik

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Ejective and preventative: the IllustrisTNG black hole feedback and its effects on the thermodynamics of the gas within and around galaxies (2020)

Zinger, Elad ; Pillepich, Annalisa ; Nelson, Dylan ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 499(1): 768-792. Published 2020 Aug 31. doi: 10.1093/mnras/staa2607.

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Beschreibung: Supermassive black holes (SMBHs) that reside at the centres of galaxies can inject vast amounts of energy into the surrounding gas and are thought to be a viable mechanism to quench star formation in massive galaxies. Here, we study the $10^{9-12.5}, mathrm{M_odot }$ stellar mass central galaxy population of the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at z = 0, and show how the three components – SMBH, galaxy, and circumgalactic medium (CGM) – are interconnected in their evolution. We find that gas entropy is a sensitive diagnostic of feedback injection. In particular, we demonstrate how the onset of the low-accretion black hole (BH) feedback mode, realized in the IllustrisTNG model as a kinetic, BH-driven wind, leads not only to star formation quenching at stellar masses $gtrsim 10^{10.5}, mathrm{M_odot }$ but also to a change in thermodynamic properties of the (non-star-forming) gas, both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs increases the average gas entropy, within the galaxy and in the CGM, lengthening typical gas cooling times from $10!-!100, mathrm{Myr}$ to $1!-!10, mathrm{Gyr}$, effectively ceasing ongoing star formation and inhibiting radiative cooling and future gas accretion. In practice, the same active galactic nucleus (AGN) feedback channel is simultaneously ‘ejective’ and ‘preventative’ and leaves an imprint on the temperature, density, entropy, and cooling times also in the outer reaches of the gas halo, up to distances of several hundred kiloparsecs. In the IllustrisTNG model, a long-lasting quenching state can occur for a heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies contains regions of low-entropy gas with short cooling times.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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The stationary points of the hierarchical three-body problem (2020)

Hansen, Bradley M S ; Naoz, Smadar

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 499(2): 1682-1700. Published 2020 Sep 03. doi: 10.1093/mnras/staa2602.

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Beschreibung: We study the stationary points of the hierarchical three body problem in the planetary limit (m1, m2 ≪ m0) at both the quadrupole and octupole orders. We demonstrate that the extension to octupole order preserves the principal stationary points of the quadrupole solution in the limit of small outer eccentricity e2 but that new families of stable fixed points occur in both prograde and retrograde cases. The most important new equilibria are those that branch off from the quadrupolar solutions and extend to large e2. The apsidal alignment of these families is a function of mass and inner planet eccentricity, and is determined by the relative directions of precession of ω1 and ω2 at the quadrupole level. These new equilibria are also the most resilient to the destabilizing effects of relativistic precession. We find additional equilibria that enable libration of the inner planet argument of pericentre in the limit of radial orbits and recover the non-linear analogue of the Laplace–Lagrange solutions in the coplanar limit. Finally, we show that the chaotic diffusion and orbital flips identified with the eccentric Kozai–Lidov mechanism and its variants can be understood in terms of the stationary points discussed here.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Diametrically Opposite Scaling of Extreme Precipitation and Streamflow to Temperature in South and Central Asia (2020)

Ghausi, Sarosh Alam ; Ghosh, Subimal

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 02. doi: 10.1029/2020gl089386.

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Publikationsdatum: 2020-09-02

Print ISSN: 0094-8276

Digitale ISSN: 1944-8007

Thema: Geologie und Paläontologie , Physik

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Robust Longitudinally Variable Responses of the ITCZ to a Myriad of Climate Forcings (2020)

Atwood, Alyssa R. ; Donohoe, Aaron ; Battisti, David S. ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 02. doi: 10.1029/2020gl088833.

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Print ISSN: 0094-8276

Digitale ISSN: 1944-8007

Thema: Geologie und Paläontologie , Physik

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Atmospheric Gravity Waves Observed in the Nightglow Following the 21 August 2017 Total Solar Eclipse (2020)

Paulino, I. ; Figueiredo, C. A. O. B. ; Rodrigues, F. S. ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 05. doi: 10.1029/2020gl088924.

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Publikationsdatum: 2020-09-05

Print ISSN: 0094-8276

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Thema: Geologie und Paläontologie , Physik

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Disentangling the Impact of the COVID‐19 Lockdowns on Urban NO 2 From Natural Variability (2020)

Goldberg, Daniel L. ; Anenberg, Susan C. ; Griffin, Debora ; [weitere]

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 05. doi: 10.1029/2020gl089269.

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Print ISSN: 0094-8276

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Thema: Geologie und Paläontologie , Physik

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Intraseasonal Surface Salinity Variability and the MJO in a Climate Model (2020)

Zhu, Jieshun ; Kumar, Arun ; Wang, Wanqiu

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Sep 02. doi: 10.1029/2020gl088997.

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Thema: Geologie und Paläontologie , Physik

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Hyporheic Exchange Under Undular Flows Over a Coarse Granular Bed (2020)

Shih, WuRong ; Wu, Fu‐Chun

American Geophysical Union

In: Geophysical Research Letters. 2020; 47(17): Published 2020 Aug 27. doi: 10.1029/2020gl089114.

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Thema: Geologie und Paläontologie , Physik

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Incorporating spatial variations in parameters for improvements of an evapotranspiration model (2020)

Wu, Genan ; Hu, Zhongmin ; Keenan, Trevor F. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Biogeosciences. 2020; Published 2020 Aug 17. doi: 10.1029/2019jg005504. [early online release]

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Publikationsdatum: 2020-08-17

Print ISSN: 2169-8953

Digitale ISSN: 2169-8961

Thema: Geologie und Paläontologie , Biologie

Publiziert von American Geophysical Union

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Mineral Nutrients Sourced in Deep Regolith Sustain Long‐Term Nutrition of Mountainous Temperate Forest Ecosystems (2020)

Uhlig, D. ; Amelung, W. ; Blanckenburg, F.

American Geophysical Union

In: Global Biogeochemical Cycles. 2020; 34(9): Published 2020 Sep 01. doi: 10.1029/2019gb006513.

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Publikationsdatum: 2020-09-01

Print ISSN: 0886-6236

Digitale ISSN: 1944-9224

Thema: Biologie , Chemie und Pharmazie , Geographie , Geologie und Paläontologie , Physik

Publiziert von American Geophysical Union

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Drones Help Bridge the Gaps in Assessing Global Change (2020)

Evans Ogden, Lesley

American Geophysical Union

In: Eos: Earth & Space Science News. 2020; 101: Published 2020 Aug 27. doi: 10.1029/2020eo148306.

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Beschreibung: New instruments in the research tool kit bolster scientific understanding of the ecology of a greening Arctic.

Print ISSN: 0096-3941

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Thema: Geologie und Paläontologie

Publiziert von American Geophysical Union

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Summer High‐Wind Events and Phytoplankton Productivity in the Arctic Ocean (2020)

Crawford, Alex D. ; Krumhardt, Kristen M. ; Lovenduski, Nicole S. ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Oceans. 2020; 125(9): Published 2020 Aug 28. doi: 10.1029/2020jc016565.

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Print ISSN: 2169-9275

Digitale ISSN: 2169-9291

Thema: Geologie und Paläontologie , Physik

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Impact of Assimilation of Moored Velocity Data on Low‐Frequency Current Estimation in Northwestern Tropical Pacific (2020)

Liu, Danian ; Wang, Fan ; Zhu, Jiang ; [weitere]

American Geophysical Union

In: Journal of Geophysical Research: Oceans. 2020; 125(9): Published 2020 Sep 01. doi: 10.1029/2019jc015829.

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Thema: Geologie und Paläontologie , Physik

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Broadband ground-motion simulation of 2016 Amatrice earthquake, Central Italy (2020)

Pischiutta, Marta ; Akinci, Aybige ; Tinti, Elisa ; [weitere]

Oxford University Press

In: Geophysical Journal International. 2020; Published 2020 Aug 31. doi: 10.1093/gji/ggaa412. [early online release]

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Beschreibung: Summary On 24th August 2016 at 01:36 UTC a ML6.0 earthquake struck several villages in central Italy, among which Accumoli, Amatrice and Arquata del Tronto. The earthquake was recorded by about 350 seismic stations, causing 299 fatalities and damage with macroseismic intensities up to 11. The maximum acceleration was observed at Amatrice station (AMT) reaching 916 cm/s2 on E-W component, with epicentral distance of 15 km and Joyner and Boore distance to the fault surface (RJB) of less than a kilometre. Motivated by the high levels of observed ground motion and damage, we generate broadband seismograms for engineering purposes by adopting a hybrid method. To infer the low frequency seismograms, we considered the kinematic slip model by Tinti et al. (2016). The high frequency seismograms were produced using a stochastic finite-fault model approach based on dynamic corner-frequency. Broadband synthetic time series were therefore obtained by merging the low and high frequency seismograms. Simulated hybrid ground motions were compared both with the observed ground motions and the ground-motion prediction equations (GMPEs), to explore their performance and to retrieve the region-specific parameters endorsed for the simulations. In the near-fault area we observed that hybrid simulations have a higher capability to detect near source effects and to reproduce the source complexity than the use of GMPEs. Indeed, the general good consistency found between synthetic and observed ground motion (both in the time and frequency domain), suggests that the use of regional-specific source scaling and attenuation parameters together with the source complexity in hybrid simulations improves ground motion estimations. To include the site effect in stochastic simulations at selected stations, we tested the use of amplification curves derived from HVRSs (horizontal-to-vertical response spectra) and from HVSRs (horizontal-to-vertical spectral ratios) rather than the use of generic curves according to NTC-18 Italian seismic design code. We generally found a further reduction of residuals between observed and simulated both in terms of time histories and spectra.

Print ISSN: 0956-540X

Digitale ISSN: 1365-246X

Thema: Geologie und Paläontologie

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Spectroscopic study of magnesium dinitrogen and sodium dinitrogen cation (2020)

Cheng, Qianyi ; Washington, Maura C ; Burns, Joseph E ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; Published 2020 Sep 03. doi: 10.1093/mnras/staa2646. [early online release]

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Beschreibung: Despite its likely importance in astrochemistry, pure rotational spectra are not observable for gas phase N2 since this molecule has no permanent dipole moment. Complexation of monomeric N2 with a cationic metal (MN2+) may be kinetically and thermodynamically favorable, and the detection of such MN2+ molecules could be useful tracers of N2 in order to probe its abundance and kinetics. Highly accurate quartic force field methods have been applied here to compute rotational and vibrational spectroscopic properties of the NaN2+ and MgN2+ molecules via a coupled cluster-based composite approach with additional corrections for post-CCSD(T) electron correlation and relativistic effects. The relative energies of various isomers have also been computed and show that both NaN2+ and MgN2+ have linear ground electronic states. At the highest level of theory, rotational constants (B0) of 4086.9 and 4106.0 MHz are predicted for NaN2+ and MgN2+, respectively, with dipole moments of 6.92 D and 4.34 D, respectively making them rotationally observable even at low concentrations. Post-CCSD(T) electron correlation corrections lower the N-N stretching frequency while relativistic corrections have a much smaller effect putting the fundamental frequencies at 2333.7 cm−1 and 2313.6 cm−1, respective of NaN2+ and MgN2+ slightly above that in N2H+. Additive corrections do not significantly change the other two vibrational modes. An anharmonic, zero-point corrected N2 dissociation energy of 7.3 and 7.0 kcal mol−1 is, respectively, reported for NaN2+ and MgN2+ suggesting possible formation of these molecules in protoplanetary disks or planetary nebulae that are metal- and nitrogen-rich.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Formation of the large nearby galaxies (2020)

Peebles, P J E

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 498(3): 4386-4395. Published 2020 Sep 01. doi: 10.1093/mnras/staa2649.

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Publikationsdatum: 2020-09-01

Beschreibung: Simulations of galaxy formation tend to place star particles in orbits seriously different from circular in numbers far larger than seem reasonable for the bulges and stellar haloes of the nearby L ∼ L* galaxies that can be examined in particularly close detail. I offer an example of how the situation might be improved: a prescription for non-Gaussian initial conditions on the scale of galaxies.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Rapid compact jet quenching in the Galactic black hole candidate X-ray binary MAXI J1535−571 (2020)

Russell, T D ; Lucchini, M ; Tetarenko, A J ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2020; 498(4): 5772-5785. Published 2020 Sep 01. doi: 10.1093/mnras/staa2650.

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Publikationsdatum: 2020-09-01

Beschreibung: We present results from six epochs of quasi-simultaneous radio, (sub-)millimetre, infrared, optical, and X-ray observations of the black hole X-ray binary MAXI J1535−571. These observations show that as the source transitioned through the hard–intermediate X-ray state towards the soft–intermediate X-ray state, the jet underwent dramatic and rapid changes. We observed the frequency of the jet spectral break, which corresponds to the most compact region in the jet where particle acceleration begins (higher frequencies indicate closer to the black hole), evolves from the infrared band into the radio band (decreasing by ≈3 orders of magnitude) in less than a day. During one observational epoch, we found evidence of the jet spectral break evolving in frequency through the radio band. Estimating the magnetic field and size of the particle acceleration region shows that the rapid fading of the high-energy jet emission was not consistent with radiative cooling; instead, the particle acceleration region seems to be moving away from the black hole on approximately dynamical time-scales. This result suggests that the compact jet quenching is not caused by local changes to the particle acceleration, rather we are observing the acceleration region of the jet travelling away from the black hole with the jet flow. Spectral analysis of the X-ray emission shows a gradual softening in the few days before the dramatic jet changes, followed by a more rapid softening ∼1–2 d after the onset of the jet quenching.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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