ALBERT

Description: Nell’ambito del progetto EDISECUR, finanziato della regione Lazio, è stato sviluppato un prototipo di telesensore infrasonico, TIS, a tracciamento di speckle per la misura della velocità angolare, delle frequenze fondamentali e delle armoniche di una superficie sottoposta a oscillazioni. Il TIS si presta particolarmente per il rilevamento e il monitoraggio nel tempo degli edifici, ponti e altri manufatti. Conoscere lo stato vibrazionale di queste strutture può essere d’interesse sia per la loro caratterizzazione dinamica che per la sicurezza. Questo prototipo, sufficientemente compatto, si presta a una misura immediata della velocità angolare e, con semplici operazioni, si possono dedurre spostamenti e accelerazioni angolari. Dalle grandezze angolari e dalla conoscenza geometrica della superficie, tramite alcuni schemi ed esempi, si mostra come sia possibile determinare anche altri parametri cinematici lineari. Il telesensore può essere impiegato nelle misure delle vibrazioni di superfici a lunga distanza di varia natura, anche laddove non fosse possibile accedere per eseguire una misura diretta. Lo strumento copre un campo di frequenze fino alle decine di Hz, ha una sensibilità e una dinamica tale da rilevare le vibrazioni indotte dal rumore industriale, dal traffico, dal vento e altro. Questo lavoro è principalmente rivolto alle applicazioni del TIS nel rilevamento delle vibrazioni delle strutture ed è in questo ambito che vengono spiegate le modalità, i limiti e i vantaggi del suo impiego insieme agli errori insiti nella tecnica di misura. Dato che il TIS misura un movimento relativo tra lo stesso strumento e la superficiebersaglio, sono stati valutati gli errori delle vibrazioni dovute alla microsismicità e altre cause ambientali. Vengono infine riportati due preliminari esempi di misura su una struttura edile.

Description: Regione Lazio, progetto EDISECUR

Description: Published

Description: 1-36

Description: 7TM.Sviluppo e Trasferimento Tecnologico

Description: JCR Journal

Description: L’Istituto Nazionale di Geofisica e Vulcanologia (INGV) riceve, nella Sala di Sorveglianza Sismica e Centro Allerta Tsunami di Roma, i segnali in tempo reale da centinaia di stazioni sismiche distribuite sul territorio nazionale. Entro due minuti dall’occorrenza di un qualsiasi terremoto, appositi sistemi automatici forniscono una prima valutazione dei parametri ipocentrali. Due sismologi, sempre presenti nella sala operativa della sede centrale, controllano le informazioni ottenute e, per i terremoti sopra una determinata soglia di magnitudo (ML ≥ 2.5), comunicano alla Sala Situazione Italia della Protezione Civile i dati elaborati, in media in circa 12 minuti (massimo entro 30 minuti) [Margheriti et al., 2021]. La valutazione definitiva dei parametri ipocentrali di tutti i terremoti, dai più grandi avvertiti in vaste aree del territorio ai più piccoli rilevati solo da pochi strumenti, è demandata a un’analisi più accurata svolta in un secondo tempo, ormai da alcuni decenni, da un gruppo di analisti specializzati nell’interpretazione dei segnali sismici. Gli analisti sismologi del Bollettino Sismico Italiano revisionano tutti i dati registrati dalle stazioni della Rete Sismica Nazionale (RSN) dell’INGV e riconoscono la presenza di terremoti attraverso un’analisi diretta delle forme d’onda. In tal modo l’analista rileva il tempo d’arrivo delle onde sismiche ai vari sensori e valuta l’ampiezza delle oscillazioni e la direzione del moto del suolo; questi parametri, utilizzati da apposite procedure di calcolo, consentono di localizzare ogni terremoto e di valutare la magnitudo associata. Le informazioni così ottenute confluiscono nel database che l’INGV gestisce e che mette a disposizione della comunità1. Questa pubblicazione ha come scopo quello di far conoscere un prodotto dell’Istituto Nazionale di Geofisica e Vulcanologia, Il Bollettino Sismico Italiano (BSI), con particolare riferimento all’anno 2015. Saranno delineate le principali caratteristiche della sismicità naturale e quella di origine antropica registrata in Italia nel corso dell’anno esaminato.

Description: Published

Description: 1-48

Description: 4IT. Banche dati

Description: JCR Journal

Description: This study represents the first attempt to combine the geomorphological characteristics of the island of Ustica with the human settlements that have been established during prehistory, with the purpose of reconstructing the interactions between communities and the natural environment from the Neolithic to the Middle Bronze Age (6th - 1st millennia B.C.). Ustica is a small island in the Southern Tyrrhenian Sea, visible but far (~55 km) from the northern coast of western Sicily. Its rugged volcanic nature, remodeled and enriched by the sea, offered to the first colonizers a wide repertoire of opportunities and challenges. This island can be treated as an ideal “laboratory” to understand how settlers, taking their first steps towards the foundation of organized communities, were able to seize opportunities or succumb to obstacles. The review of archaeological research until now carried out in Ustica, integrated with geomorphological data and other biogeographical indicators, offers a picture of the prehistory of Ustica in which human presence is continuous and distributed in various sites of the island characterized by different physiographic characteristics. There are phases dominated by the choice of naturally protected sites and phases in which settlements expands on open land, suitable for agricultural use. Where the archaeological evidence is scarce, the geomorphological peculiarities allow us to decipher the vocations and characters of a human settlement. The study leads to an open question: in the Middle Bronze Age, after about five thousand years of uninterrupted habitation of Ustica, which factors, geological, social, or other, induced the early communities to abandon the island, without returning there for about eight centuries, until the Hellenistic-Roman age?

Description: Published

Description: VO550

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

Description: JCR Journal

Description: This work sets out to identify a state-of-the-art system to be used for the calibration of seismic sensors. The aim is to acquire such a system within the framework of the PON ARS01 00926 EWAS (an Early Warning System for cultural heritage) project, which seeks to develop new technologies for the protection, conservation and safety of cultural heritage and envisages creating a newly developed seismic monitoring system. This system will exploit the ETL3D/5s-H hybrid sensors, resulting from the integration of a precision accelerometer within the ETL3D/5s velocimeter [Fertitta et al., 2020]. The new calibration system, already acquired and being installed, can be used by the EWAS project partners (including the National Institute of Geophysics and Volcanology and the Kore University of Enna), to calibrate the ETL3D/5s-H sensors, and by external organisations to calibrate or gauge other seismic sensors, thus providing a useful service to the scientific community and supporting industrial activities. This paper presents the method used and the activities undertaken to define the technical specifications of the calibration system. A feasibility study of an electromechanical vibrating table and the testing of two electrodynamic calibration systems were carried out. One of the electrodynamic systems is the CS18P (Calibration System for Seismic Sensors) produced by the German firm SPEKTRA. The CS18P comprises two vibrating tables, one horizontal and one vertical, which, thanks to their fluid-dynamic suspension, eliminate the sliding and rolling friction associated with the movement of the moving part with respect to the fixed part. A hardware and software system monitors and controls the motion in real time, analyses the data and automatically processes a predefined set of measurements. In the light of the technical specifications and experimental results, the CS18P represents the ideal solution for the aims of the EWAS project and also in view of the possible future uses of the calibration system.

Description: Published

Description: 1-38

Description: 2IT. Laboratori analitici e sperimentali

Description: JCR Journal

Description: In recent years, new approaches for developing earthquake rupture forecasts (ERFs) have been proposed to be used as an input for probabilistic seismic hazard assessment (PSHA). Zone- based approaches with seismicity rates derived from earthquake catalogs are commonly used in many countries as the standard for national seismic hazard models. In Italy, a single zone- based ERF is currently the basis for the official seismic hazard model. In this contribution, we present eleven new ERFs, including five zone-based, two smoothed seismicity-based, two fault- based, and two geodetic-based, used for a new PSH model in Italy. The ERFs were tested against observed seismicity and were subject to an elicitation procedure by a panel of PSHA experts to verify the scientific robustness and consistency of the forecasts with respect to the observations. Tests and elicitation were finalized to weight the ERFs. The results show a good response to the new inputs to observed seismicity in the last few centuries. The entire approach was a first attempt to build a community-based set of ERFs for an Italian PSHA model. The project involved a large number of seismic hazard practitioners, with their knowledge and experience, and the development of different models to capture and explore a large range of epistemic uncertainties in building ERFs, and represents an important step forward for the new national seismic hazard model.

Description: Published

Description: SE220

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

Description: JCR Journal

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 125(6), (2020): e2019JB019239, doi:10.1029/2019JB019239.

Description: P‐to‐S‐converted waves observed in controlled‐source multicomponent ocean bottom seismometer (OBS) records were used to derive the Vp/Vs structure of Cascadia Basin sediments. We used P‐to‐S waves converted at the basement to derive an empirical function describing the average Vp/Vs of Cascadia sediments as a function of sediment thickness. We derived one‐dimensional interval Vp/Vs functions from semblance velocity analysis of S‐converted intrasediment and basement reflections, which we used to define an empirical Vp/Vs versus burial depth compaction trend. We find that seaward from the Cascadia deformation front, Vp/Vs structure offshore northern Oregon and Washington shows little variability along strike, while the structure of incoming sediments offshore central Oregon is more heterogeneous and includes intermediate‐to‐deep sediment layers of anomalously elevated Vp/Vs. These zones with elevated Vp/Vs are likely due to elevated pore fluid pressures, although layers of high sand content intercalated within a more clayey sedimentary sequence, and/or a higher content of coarser‐grained clay minerals relative to finer‐grained smectite could be contributing factors. We find that the proto‐décollement offshore central Oregon develops within the incoming sediments at a low‐permeability boundary that traps fluids in a stratigraphic level where fluid overpressure exceeds 50% of the differential pressure between the hydrostatic pressure and the lithostatic pressure. Incoming sediments with the highest estimated fluid overpressures occur offshore central Oregon where deformation of the accretionary prism is seaward vergent. Conversely, landward vergence offshore northern Oregon and Washington correlates with more moderate pore pressures and laterally homogeneous Vp/Vs functions of Cascadia Basin sediments.

Description: This research was funded by National Science Foundation (NSF) Grant OCE‐1657237 to J. P. C, OCE‐1657839 to A. F. A. and S. H., and OCE‐1657737 to S. M. C. Data used in this study were acquired with funding from NSF Grants OCE‐1029305 and OCE‐1249353. Data used in this research were provided by instruments from the Ocean Bottom Seismic Instrument Center (http://obsic.whoi.edu, formerly OBSIP), which is funded by the NSF. OBSIC/OBSIP data are archived at the IRIS Data Management Center (http://www.iris.edu) under network code X6 (https://doi.org/10.7914/SN/X6_2012). Data processing was conducted with Emerson‐Paradigm Software package Echos licensed to Woods Hole Oceanographic Institution under Paradigm Academic Software Program and MATLAB package SeismicLab of the University of Alberta, Canada (http://seismic-lab.physics.ualberta.ca), under GNU General Public License (MATLAB® is a registered trademark of MathWorks).

Description: 2020-11-28

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016068, doi:10.1029/2020JC016068.

Description: Labrador Sea Water (LSW) is a major component of the deep limb of the Atlantic Meridional Overturning Circulation, yet LSW transport pathways and their variability lack a complete description. A portion of the LSW exported from the subpolar gyre is advected eastward along the North Atlantic Current and must contend with the Mid‐Atlantic Ridge before reaching the eastern basins of the North Atlantic. Here, we analyze observations from a mooring array and satellite altimetry, together with outputs from a hindcast ocean model simulation, to estimate the mean transport of LSW across the Charlie‐Gibbs Fracture Zone (CGFZ), a primary gateway for the eastward transport of the water mass. The LSW transport estimated from the 25‐year altimetry record is 5.3 ± 2.9 Sv, where the error represents the combination of observational variability and the uncertainty in the projection of the surface velocities to the LSW layer. Current velocities modulate the interannual to higher‐frequency variability of the LSW transport at the CGFZ, while the LSW thickness becomes important on longer time scales. The modeled mean LSW transport for 1993–2012 is higher than the estimate from altimetry, at 8.2 ± 4.1 Sv. The modeled LSW thickness decreases substantially at the CGFZ between 1996 and 2009, consistent with an observed decline in LSW volume in the Labrador Sea after 1994. We suggest that satellite altimetry and continuous hydrographic measurements in the central Labrador Sea, supplemented by profiles from Argo floats, could be sufficient to quantify the LSW transport at the CGFZ.

Description: A. G. N. appreciates conversations with Kathy Donohue, Tom Rossby and Lisa Beal, which helped to interpret the results. J. B. P. acknowledges support from NSF through Grant OCE‐1947829. The authors thank all colleagues and ship crew involved in the R/V Meteor cruise M‐82/2 and Maria S. Merian cruise MSM‐21/2. The mooring data presented in this paper were funded by NSF through Grant OCE‐0926656.

Description: 2021-01-03

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(3), (2020): e2019GL086703, doi:10.1029/2019GL086703.

Description: Salt marsh assessments focus on vertical metrics such as accretion or lateral metrics such as open‐water conversion, without exploration of how the dimensions are related. We exploited a novel geospatial data set to explore how elevation is related to the unvegetated‐vegetated marsh ratio (UVVR), a lateral metric, across individual marsh “units” within four estuarine‐marsh systems. We find that elevation scales consistently with the UVVR across systems, with lower elevation units demonstrating more open‐water conversion and higher UVVRs. A normalized elevation‐UVVR relationship converges across systems near the system‐mean elevation and a UVVR of 0.1, a critical threshold identified by prior studies. This indicates that open‐water conversion becomes a dominant lateral instability process at a relatively conservative elevation threshold. We then integrate the UVVR and elevation to yield lifespan estimates, which demonstrate that higher elevation marshes are more resilient to internal deterioration, with an order‐of‐magnitude longer lifespan than predicted for lower elevation marshes.

Description: This study was supported by the USGS through the Coastal Marine Hazards/Resources Program, the National Park Service through the Natural Resource Preservation Program, and the U.S. Fish and Wildlife Service through the Science Support Partnership. Erika Lentz, Elizabeth Pendleton, Meagan Gonneea, Joel Carr, and two anonymous reviewers provided constructive advice on the study. S.F. was partly supported by US National Science Foundation award 1637630 (PIE LTER), 1832221 (VCR LTER). The geospatial data used in this study are published in the Coastal Wetlands Synthesis Products catalog on ScienceBase (https://www.sciencebase.gov/catalog/item/5b73325ee4b0f5d5787c5ff3).

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research- Biogeosciences 125(4), (2020): e2019JG005158, doi:10.1029/2019JG005158.

Description: Long‐term soil warming can decrease soil organic matter (SOM), resulting in self‐reinforcing feedback to the global climate system. We investigated additional consequences of SOM reduction for soil water holding capacity (WHC) and soil thermal and hydrological buffering. At a long‐term soil warming experiment in a temperate forest in the northeastern United States, we suspended the warming treatment for 104 days during the summer of 2017. The formerly heated plot remained warmer (+0.39 °C) and drier (−0.024 cm3 H2O cm−3 soil) than the control plot throughout the suspension. We measured decreased SOM content (−0.184 g SOM g−1 for O horizon soil, −0.010 g SOM g−1 for A horizon soil) and WHC (−0.82 g H2O g−1 for O horizon soil, −0.18 g H2O g−1 for A horizon soil) in the formerly heated plot relative to the control plot. Reduced SOM content accounted for 62% of the WHC reduction in the O horizon and 22% in the A horizon. We investigated differences in SOM composition as a possible explanation for the remaining reductions with Fourier transform infrared (FTIR) spectra. We found FTIR spectra that correlated more strongly with WHC than SOM, but those particular spectra did not differ between the heated and control plots, suggesting that SOM composition affects WHC but does not explain treatment differences in this study. We conclude that SOM reductions due to soil warming can reduce WHC and hydrological and thermal buffering, further warming soil and decreasing SOM. This feedback may operate in parallel, and perhaps synergistically, with carbon cycle feedbacks to climate change.

Description: We would like to acknowledge Jeffery Blanchard, Priya Chowdhury, Kristen DeAngelis, Luiz Dominguez‐Horta, Kevin Geyer, Rachelle Lacroix, Xaiojun Liu, William Rodriguez, and Alexander Truchonand and for assistance with field sampling. We would like to acknowledge Michael Bernard for assistance with field sampling and lab work. We would like to acknowledge Aaron Ellison for statistical consultation. This research was financially supported by the U.S. National Science Foundation's Long Term Ecological Research Program (NSF‐DEB‐0620443 and NSF‐DEB‐1237491), the Long Term Research in Environmental Biology Program (NSF DEB‐1456528) , and the U.S. Department of Energy (DOE‐DE‐SC0005421 and DOE‐DE‐SC0010740). Data used in this study are available from the Harvard Forest Data Archive (Datasets HF018‐03, HF018‐04, and HF018‐13), accessible at https://harvardforest.fas.harvard.edu/harvard‐forest‐data‐archive.

Description: 2020-10-04

Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(9), (2020): 3845-3862, doi:10.1175/JCLI-D-19-0215.1.

Description: The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.

Description: The authors gratefully acknowledge support from the Physical Oceanography Program of the U.S. National Science Foundation (Awards OCE-1756143 and OCE-1537136) and the Climate Program Office of the National Oceanic and Atmospheric Administration (Award NA15OAR4310088). Gratitude is extended to Claus Böning and Arne Biastoch who shared ORCA025 output. S. Zou thanks F. Li, M. Buckley, and L. Li for helpful discussions. We also thank three anonymous reviewers for helpful suggestions.

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016445, doi:10.1029/2020JC016445.

Description: The Mid‐Atlantic Bight (MAB) Cold Pool is a bottom‐trapped, cold (temperature below 10°C) and fresh (practical salinity below 34) water mass that is isolated from the surface by the seasonal thermocline and is located over the midshelf and outer shelf of the MAB. The interannual variability of the Cold Pool with regard to its persistence time, volume, temperature, and seasonal along‐shelf propagation is investigated based on a long‐term (1958–2007) high‐resolution regional model of the northwest Atlantic Ocean. A Cold Pool Index is defined and computed in order to quantify the strength of the Cold Pool on the interannual timescale. Anomalous strong, weak, and normal years are categorized and compared based on the Cold Pool Index. A detailed quantitative study of the volume‐averaged heat budget of the Cold Pool region (CPR) has been examined on the interannual timescale. Results suggest that the initial temperature and abnormal warming/cooling due to advection are the primary drivers in the interannual variability of the near‐bottom CPR temperature anomaly during stratified seasons. The long persistence of temperature anomalies from winter to summer in the CPR also suggests a potential for seasonal predictability.

Description: This work was funded by the National Oceanic and Atmospheric Administration through Awards NOAA‐NA‐15OAR4310133 and NOAA‐NA‐13OAR4830233 and the National Science Foundation Awards OCE‐1049088, OCE‐1419584, and OCE‐0961545.

Description: 2021-02-03

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016197, doi:10.1029/2020JC016197.

Description: Synoptic shipboard measurements, together with historical hydrographic data and satellite data, are used to elucidate the detailed structure of the Atlantic Water (AW) boundary current system in the southern Canada Basin and its connection to the upstream source of AW in the Chukchi Borderland. Nine high‐resolution occupations of a transect extending from the Beaufort shelf to the deep basin near 152°W, taken between 2003 and 2018, reveal that there are two branches of the AW boundary current that flow beneath and counter to the Beaufort Gyre. Each branch corresponds to a warm temperature core and transports comparable amounts of Fram Strait Branch Water between roughly 200–700 m depth, although they are characterized by a different temperature/salinity (T/S) structure. The mean volume flux of the combined branches is 0.87 ± 0.13 Sv. Using the historical hydrographic data, the two branches are tracked upstream by their temperature cores and T/S signatures. This sheds new light on how the AW negotiates the Chukchi Borderland and why two branches emerge from this region. Lastly, the propagation of warm temperature anomalies through the region is quantified and shown to be consistent with the deduced circulation scheme.

Description: This work was funded by the following sources: National Science Foundation Grants PLR‐1504333, OPP‐1733564, and OPP‐1504394; National Oceanic and Atmospheric Administration Grant NA14OAR4320158; and National Aeronautics and Space Administration Grant NNX10AF42G.

Description: 2021-01-27

Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Hahn, L. C., Storelvmo, T., Hofer, S., Parfitt, R., & Ummenhofer, C. C. Importance of Orography for Greenland cloud and melt response to atmospheric blocking. Journal of Climate, 33(10), (2020): 4187-4206, doi:10.1175/JCLI-D-19-0527.1.

Description: More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet.

Description: This research was supported by the Woods Hole Oceanographic Institution Summer Student Fellow program, by the U.S. National Science Foundation under AGS-1355339 to C.C.U., and by the European Research Council through Grant 758005.

Description: Mobile network routers in seismic and volcanic surveillance

Description: Published

Description: 1-36

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: N/A or not JCR

Description: This special issue of “Annals of Geophysics” concerns the dissemination of knowledge on the prevention of damage mainly due to non-structural elements during earthquakes and its practical application at houses, schools and offices by common citizens, companies and institutions. The seismic capacity of buildings and other civil engineering structures and infrastructures are object of regulations for design and construction, and in some cases also the design, fabrication and mounting of electrical and mechanical equipments. Consequently, even in strong earthquakes many collapses of buildings and infrastructures are avoided. However, with few exceptions, design procedures do not aim at avoiding seismic vibrations from being transferred to the structures, but enable the structures to resist to the effects of those vibrations

Description: European Commission’s Humanitarian Aid and Civil Protection (Grant agreement ECHO/SUB/2015/718655/PREV28)

Description: Published

Description: SE331

Description: 3TM. Comunicazione

Description: JCR Journal

Description: Encouraging property owners and individuals to adopt mitigation measures to improve the resilience of their buildings and equipments to seismic hazard has been a major challenge in many earthquake- prone countries. Few business leaders are aware of the fragility of their supply chains or other critical systems due to earthquake hazard. Bridging the gap between research production and research use is another crucial challenge for the earthquake risk research process. The KnowRISK project outcome is aimed at encouraging the proactive engagement of multi- stakeholders (community at large, schools, business community and local govern-ment groups) undertaking non-structural mitigation measures that will minimize earthquake losses to individuals and communities. Engaging stakeholders, taking into account their needs and inputs to maintain critical and urgent business activities, can contribute to the research findings and ensure that our data collection is thorough and complete. Engagement with stakeholders, during the whole process can lead to improved outcomes and for the development of viable solutions, for business and society, because of stakeholder’s role and influence within the organizations.

Description: European Commission’s Humanitarian Aid and Civil Protection (Grant agreement ECHO/SUB/2015/718655/PREV28)

Description: Published

Description: SE324

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

Description: JCR Journal

Description: The focus of this study is the analysis of a cave in Central Italy, the Beatrice Cenci cave, in order topoint out and constrain evidence of possible past earthquakes and of fault activity in the area. Weperformed a survey of seismic related damages within the cave. This included the analysis ofbroken/collapsed speleothems, the recognition of structural collapse, of tilting/growth alteration inthe speleothems, and the mapping of fractures, joints and/or faults. To timely set the occurrence ofthe recognized damage, organic sediments were dated with 14C radiocarbon method. The resultsmerged toward the recognition of two distinct seismic shaking events affecting the caveenvironment, one older than 30 kyr and another around 7 kyr. The deformation observed withinthe cave led us to the hypothesis that the events of damage were possibly linked to the activity ofthe regional tectonic lineament that crosses the cave, i.e., the Liri normal fault. The morphology andthe evolution of the cave appear controlled by the fault zone. These speleoseismological resultsprovided a new contribution on the knowledge of the past activity of the Liri fault and on theearthquake history of this sector of Central Apennines.

Description: INGV

Description: Published

Description: SE435

Description: 2T. Deformazione crostale attiva

Description: JCR Journal

Description: To examine the atmospheric responses to Arctic sea ice variability in the Northern Hemisphere cold season (from October to the following March), this study uses a coordinated set of large-ensemble experiments of nine atmospheric general circulation models (AGCMs) forced with observed daily varying sea ice, sea surface temperature, and radiative forcings prescribed during the 1979–2014 period, together with a parallel set of experiments where Arctic sea ice is substituted by its climatology. The simulations of the former set reproduce the near-surface temperature trends in reanalysis data, with similar amplitude, and their multimodel ensemble mean (MMEM) shows decreasing sea level pressure over much of the polar cap and Eurasia in boreal autumn. The MMEM difference between the two experiments allows isolating the effects of Arctic sea ice loss, which explain a large portion of the Arctic warming trends in the lower troposphere and drive a small but statistically significant weakening of the wintertime Arctic Oscillation. The observed interannual covariability between sea ice extent in the Barents–Kara Seas and lagged atmospheric circulation is distinguished from the effects of confounding factors based on multiple regression, and quantitatively compared to the covariability in MMEMs. The interannual sea ice decline followed by a negative North Atlantic Oscillation–like anomaly found in observations is also seen in the MMEM differences, with consistent spatial structure but much smaller amplitude. This result suggests that the sea ice impacts on trends and interannual atmospheric variability simulated by AGCMs could be underestimated, but caution is needed because internal atmospheric variability may have affected the observed relationship.

Description: Published

Description: 8419–8443

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: Il presente lavoro raccoglie alcune esperienze di Progetti di Alternanza Scuola Lavoro (d’ora in poi ASL) realizzati dall’INGV negli anni scolastici dal 2015 al 2019 e dedicati al rischio sismico, alle scienze polari ed agli strumenti per la divulgazione scientifica. Le esperienze descrivono il lavoro realizzato da un gruppo di ricercatori INGV con competenze in diversi ambiti disciplinari (sismologia, geologia, vulcanologia fisica dell’atmosfera, psicologia) e in alcuni casi le attività sono state svolte in collaborazione con ricercatori di altri enti. Il gruppo di lavoro è composto da ricercatori che da molti anni dedicano parte del loro tempo-lavoro alle attività di divulgazione scientifica, ai progetti educativi, alla didattica della scienza. In una parola a quella che oggi rappresenta, per gli enti di ricerca, la “Terza missione”, ovvero l’insieme di tutte le attività finalizzate a creare una connessione bidirezionale tra il mondo della ricerca e la società. Ciò che ha caratterizzato l’approccio dei ricercatori INGV ai progetti ASL, sia nella fase di progettazione che di realizzazione, è la finalità di consentire agli studenti di vivere un’esperienza reale ed immersiva in un contesto di lavoro. E quindi l’opportunità di sperimentare capacità e abilità che caratterizzano il contesto organizzativo (diritti, doveri, responsabilità, impegni, regole), diversamente dal mondo della scuola. Il secondo aspetto al quale ci si è riferiti nella realizzazione dei progetti è quello di consentire agli studenti di esplorare, in particolare il contesto delle attività lavorative connesse al mondo della ricerca. Da questo punto di vista gli studenti hanno potuto acquisire conoscenze in ambiti tematici specifici, hanno avuto modo di sperimentare metodi e tecniche proprie del mondo della ricerca e di acquisire capacità e abilità trasversali come il lavoro in gruppo. Il contributo è organizzato in tre capitoli in relazione ai temi affrontati nei progetti. Nel primo sono riportate le schede dei tre progetti dedicate al tema Terremoto; nel secondo vengono descritti i due progetti dedicati alla Divulgazione Scientifica e nel terzo un progetto sulle Scienze Polari. Per rendere maggiormente fruibile la lettura, ogni progetto viene descritto attraverso una scheda sintetica che evidenza le caratteristiche principali: titolo, referenti INGV, studenti partecipanti, periodo, descrizione delle attività, obiettivi e considerazioni sull’esperienza. Nel capitolo conclusivo viene proposto un bilancio delle esperienze realizzate, evidenziando punti di forza e aree di miglioramento dei progetti, con la finalità di condividere suggerimenti ed idee per tracciare percorsi formativi maggiormente efficaci nel futuro.

Description: Published

Description: 119-131

Description: 2TM. Divulgazione Scientifica

Description: N/A or not JCR

Description: “Move, protect, secure” were the three key points that the KnowRISK (Know your city, Reduce seISmic risK through non-structural elements) project posed at the core of its communication and dissemination strategy. This three key points enable each person, professional or not, to reduce non-structural damage caused by earthquakes. Dissemination is usually the last but never the least step of a communication plan, and indeed it played a crucial role in KnowRISK project for conveying the three key-point message to the widest audience. Standard dissemination activities, such as open-door events, and internet allowed us to achieve a wide spreading of ideas and best practices, reaching more than 4,000 non-professionals and almost 50,000 page views of the KnowRISK project website (in three years), respectively. As communication was recipient-targeted, the dissemination task of the project was addressed to professionals, layman, and schools. In particular, schools were chosen in order to profit from the chain-reaction action that is capable to spread a message from students to the surrounding environment.

Description: This study was co-financed by the European Commission’s Humanitarian Aid and Civil Protection through the European project KnowRISK (Know your city, Reduce seISmic risK through non-structural elements; Grant agreement ECHO/SUB/2015/718655/PREV28).

Description: Published

Description: SE328

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

Description: JCR Journal

Description: We present the commented transcription of three rare articles published in 19091910 by Father Atto Maccioni o.f.m. This friar is one of the least known among the many ecclesiastics who cultivated seismology from the 18th century onwards. Maccioni, from 1908 to 1926, managed a seismic observatory at the Sienese convent of the Osservanza. He devised an “Avvisatore”: a device equipped with a modified coherer with respect to those adopted in radiotelegraphic communications, aimed to detect natural radio signals associated with earthquakes. From the few available results it seems that the scholar obtained positive feedback, but the most interesting aspect of the story is that until now it was generally believed that this kind of research began only quite recently [Warwick, 1982]. On the contrary Maccioni may have been the first ever to study a possible electromagnetic precursor, more than a century ago.

Description: Presentiamo la trascrizione commentata di tre rari articoli pubblicati nel 19091910 da padre Atto Maccioni o.f.m., uno dei meno noti tra i tanti ecclesiastici che si sono occupati di sismologia dal XVIII secolo in poi. Maccioni, che dal 1908 al 1926 gestì un osservatorio sismico presso il convento senese dell’Osservanza, aveva ideato l’Avvisatore, un dispositivo munito di un coherer diverso da quelli radiotelegrafici e destinato a rilevare segnali radio naturali associati ai terremoti. Dai pochi risultati disponibili sembra che lo studioso abbia avuto dei riscontri positivi ma l’aspetto più interessante della vicenda è che finora si era creduto che ricerche di questo tipo fossero iniziate solo molto di recente [Warwick, 1982]. Invece Maccioni potrebbe essere stato il primo al mondo a studiare, più di un secolo fa, un ipotetico precursore elettromagnetico.

Description: Published

Description: 1-32

Description: 7T. Variazioni delle caratteristiche crostali e "precursori"

Description: 2TM. Divulgazione Scientifica

Description: N/A or not JCR

Description: La Cromatografia Ionica (IC) è diventata una delle tecniche analitiche più utilizzate nella determinazione degli anioni (F-, Cl-, Br-, NO3-, SO42-) e dei cationi (Li+, Na+, K+, Mg2+, Ca2+) in soluzioni acquose, anche a basse concentrazioni. Nel Laboratorio dell’INGV Sezione di Palermo questa tecnica viene utilizzata per determinare la composizione chimica di acque naturali (acque sotterranee, termali, meteoriche, marine), di fluidi fumarolici, campionati tramite il metodo delle ampolle di Giggenbach e delle specie acide emesse dai pennacchi vulcanici campionati con trappole alcaline. Ogni anno nel laboratorio vengono analizzati numerosi campioni per scopi di ricerca e monitoraggio geochimico e ambientale. Uno dei principali problemi dell’attività analitica di routine è la valutazione della precisione del dato, definita dall’American Public Health Association [1999], “come la misura del grado di accordo tra analisi replicate di un campione, di solito espresse come deviazione standard”. Tralasciando I problemi di rappresentatività del campione, ci sono diversi fattori che contribuiscono alla precisione, come il pretrattamento del campione, la preparazione e conservazione delle miscele di calibrazione, la ripetibilità delle misure delle aree dei picchi delle miscele di calibrazione e il tipo di calibrazione. In questo lavoro mostriamo la precisione dei cromatografi Dionex ICS-1100 ripetendo più volte l’analisi le miscele di calibrazione durante una singola sessione analitica, e la ripetibilità dello strumento, elaborando I risultati ottenuti analizzando le stesse miscele di calibrazione in differenti sessioni analitiche nell’arco di 12 mesi. Infine, viene determinata l’accuratezza del metodo attraverso l’analisi di un campione certificato. L’accuratezza è la vicinanza tra il valore osservato ed il valore vero, o comunque accettato come tale. I dati riportati in questo rapporto tecnico si riferiscono alle condizioni analitiche per le analisi di routine, con la configurazione strumentale corrente in uso presso questo laboratorio; queste possono essere ottimizzate per altri range di utilizzo a condizione però che vengano eseguite le necessarie verifiche di precisione e accuratezza.

Description: Istituto Nazionale di Geofisica e Vulcanologia (INGV) “Sez. di Palermo”

Description: Published

Description: 1-22

Description: 2IT. Laboratori analitici e sperimentali

Description: N/A or not JCR

Description: A new indirect method of estimating in situ soil air permeability is presented in this technical report. The new method is simply based on the measurement of air pressure (probe pressure) generated by pumping a constant air flux inside a special designed probe inserted into the soil. To calibrate the method, some measurements of the probe pressure were performed in some soils of the island of Vulcano, characterized by different values of the air permeability. Furthermore, technical aspects of a new device for performing continuous acquisition of the air permeability based on the new indirect method, were also described

Description: Istituto Nazionale di Geofisica e Vulcanologia (INGV) “Sez. di Palermo”

Description: Published

Description: 1-18

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: N/A or not JCR

Description: La determinazione di anioni inorganici nelle acque naturali, sotterranee e superficiali, cosi come nelle acque reflue e potabili, è una delle applicazioni più importanti della cromatografia ionica (IC). Con questa tecnica si possono comunemente determinare i principali anioni inorganici: fluoruro, cloruro, bromuro, nitrato e solfato. Utilizzando specifiche metodologie oltre ai predetti analiti, si può determinare anche il fosfato durante la medesima analisi. La determinazione dei fosfati nelle acque riveste una notevole importanza in considerazione del fatto che il fosfato rappresenta un possibile indice di inquinamento per la presenza di questa sostanza in moltissimi composti chimici, quali: detersivi domestici ed industriali, fertilizzanti ecc. La quantità di fosfati, nelle acque naturali, quando è di origine minerale e non indica inquinamento, raggiunge concentrazioni appena dosabili, mentre concentrazioni elevate e quindi misurabili, sono indice di inquinamento. Il fosfato è uno dei nutrienti di maggiore importanza nelle acque, la sua presenza in concentrazioni consistenti, può essere responsabile di manifestazioni eutrofiche ed ipertrofiche nelle acque superficiali. Data la sua importanza nel condizionare il funzionamento degli ecosistemi acquatici, esso è incluso nella lista dei cosiddetti macrodescrittori utilizzati per definire lo stato chimico delle acque fluviali e lacustri e per valutare, lo stato trofico delle acque. La determinazione del fosfato viene comunemente effettuata utilizzando l’analisi spettrofotometrica dell’eteropoliacido fosfomolibdico formatosi in seguito alla reazione con molibdato in ambiente acido ed in presenza di idoneo riducente. Tuttavia questo, metodo ampliamente utilizzato, consente la determinazione del singolo analita e non consente quindi la caratterizzazione chimica del campione. La cromatografia ionica, invece, presenta il vantaggio di essere una tecnica multi-elementare che consente di determinare in breve tempo tutti i costituenti maggiori disciolti nelle acque. In questo rapporto tecnico viene descritta la determinazione del fosfato e dei costituenti maggiori nelle acque naturali utilizzando, un cromatografo Thermo Scientific Dionex ICS 5000+, equipaggiato con una colonna a scambio anionico “Dionex AS19 4µm”, un generatore di eluente a idrossido di potassio (KOH), un soppressore elettrochimico ed un rivelatore a cella conduttimetrica.

Description: Istituto Nazionale di Geofisica e Vulcanologia (INGV) “Sez. di Palermo”

Description: Published

Description: 1-22

Description: 2IT. Laboratori analitici e sperimentali

Description: N/A or not JCR

Description: Il sito delle “Ciampate del diavolo”, sul fianco nord­orientale del vulcano Roccamonfina, è un sito unico al Mondo grazie alle sue peculiarità geologiche ed antropologiche. Il ritrovamento di impronte di hominini al di sopra di un deposito ignimbritico, impresse in nel periodo di maggiore attività del vulcano, dà spazio a numerose questioni circa le condizioni paleoambientali esistenti sul vulcano ed i complessi processi che hanno permesso la formazione e la conservazione delle impronte. La nota dedica particolare attenzione al contesto dell’attività del vulcano ed alle caratteristiche della serie dei Tufi Leucitici Bruni, in quanto le impronte note come “Ciampate del diavolo” sono presenti sulla superficie di una delle unità più alte della sequenza di questi tufi. The “Ciampate del diavolo” geosite is unique in the World due to its geological and anthropological peculiarities. Finding hominin footprints on the ignimbrite deposits of 350,000 years ago, imprinted in the period of greatest activity of the volcano, opens up numerous questions about the palaeoenvironmental conditions of the volcano and the complex processes that allowed the generation and conservation of the footprints. The note pays particular attention to the framing of the volcano's activity and to the features of deposits of the Brown Leucitic Tuff series, as the human fossil footprints known as "Ciampate del Diavolo" are preserved on the surface of one of the highest units in the sequence.

Description: Published

Description: 49-55

Description: 1V. Storia eruttiva

Description: 5V. Processi eruttivi e post-eruttivi

Description: 1TR. Georisorse

Description: 6SR VULCANI – Servizi e ricerca per la società

Description: N/A or not JCR

Description: Mts. Simbruini karst aquifer feeds important springs whose capture contributes to the water supply of Rome City. To improve the geochemical characterization of this aquifer, we analyzed 36 groundwater samples, 29 from springs and 7 from shallow wells, collected in 1996 and 2019. Atomic adsorption spectroscopy, titration, ionic chromatography and mass spectrometry were the used analytical methods. Groundwater is bicarbonate alkaline-earth type and HCO3- dominance confirms that the aquifer is hosted in carbonate rocks. Total alkalinity vs. cations plot indicates that CO2 driven weathering controls the water chemistry. The probability plots of HCO3-, cations and Ca2+ +Mg2+ indicate four groundwater populations with the less represented one (9 samples)characterized by the highest PCO2 values (〉 0.3 atm). Most anomalous values of the dissolved PCO2are from springs located near the center of the studied area. Four samples have negative values of𝛿13CCO2 (about -22‰ vs. PDB), indicating its organic origin, but two other samples have positivevalues (1.6 and 2.6 ‰ vs. PDB), similar to those observed in the CO2 of deep origin discharged atthe close Colli Albani volcano. Therefore, geochemical evidence indicates that the Mts. Simbruiniaquifer is locally affected by the input of deep originated CO2, likely rising up along fractures, interacting with a recharge of meteoric origin, as evidenced by its 𝛿2H and 𝛿18O isotopic signatures.

Description: Published

Description: HS659

Description: 1TR. Georisorse

Description: JCR Journal

Description: Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments. We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10 °C July isotherm at 72° Northern Latitude in the Laptev Sea region. During the LENA2018 expedition, we set up plots for plant projective cover and Above Ground Biomass (AGB) and sampled shrubs for shrub-ring analyses. AGB is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. AGB data and shrub age data clearly show a separation between i) low disturbance landscape types with dominant AGB moss contribution, but always low vascular plant AGB (〈0.5 kg m-2) characterised by old shrubs of several decades of stand age versus ii) a much higher vascular plant AGB contribution (〉 0.5 kg m-2) with only young shrubs in high disturbance regimes. The low disturbance regimes are represented on the Holocene and Pleistocene delta terraces in form of azonal polygonal tundra complexes and softly dissected valleys with zonal tussock tundra. In contrast, the high disturbance regimes are sites of thermo-erosion such as along thermo-erosional valleys and on floodplains. We upscaled AGB and above ground carbon pool ages using a Sentinel-2 satellite acquisition from early August 2018. We classified via classification training using Elementary Sampling Units that are the 30 m x 30 m vegetation field plots. We then used the land cover classes and grouped them according to their settings either in high disturbance or low disturbance regimes with each associated AGB value ranges and shrub age regimes. We also evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under https://doi.org/10.1594/PANGAEA.897916 and https://doi.org/10.1594/PANGAEA.897045. ESA GlobPermafrost land cover and vegetation height remote sensing products and our Sentinel-2 derived AGB product for the central Lena Delta shows realistic spatial patterns of landcover classes and biomass distribution at landscape level. However, in all products, the high biomass patches of high shrubs in the tundra landscape could not spatially be resolved as they are confined to patchy and linear distribution, not representing large enough areas suitable for upscaling. We found that high disturbance regimes with linked high and rapid AGB fluxes are distributed mainly on the floodplains and as patches along thermoerosioal features, e.g. valleys. Whereas the low disturbance landscapes on Yedoma upland tundra and Holocene terraces occur with larger area coverage representing decades slower and in magnitude smaller AGB fluxes.

Description: The best chance to achieve a future disaster-resilient society is through risk education in School: it has a great potential to strengthen capacity of communities to mitigate risks. The KnowRISK (Know your city, Reduce seISmic risK through non-structural elements) project took this opportunity and implemented a risk communication campaign for schools in Portugal, Italy, and Iceland. The idea was that suitably changes in people’s knowledge and attitude can trigger best practices. Crucial to reach such target is the raise of awareness on meaningful issues. The main challenge of the campaign was how to effectively address the mitigation of the vulnerability to earthquakes of non-structural elements, which is an issue considered to be of low priority even in the building regulations of many countries around the world. The campaign stood on a communication strategy that was systematized within a protocol, for 13- 15 years old students, that specifies goals, contents, learning strategy, support material, and relies on face-to-face intervention of scientists in the classroom. This protocol had training sessions bounded by assessment sessions, ex-ante and ex-post, that allowed to validate its efficacy. The training made large use of flipped learning and Episode of Situated Learning (EAS) strategy to raise student’s motivation and increase achievements. To ensure its replicability, the protocol was tested in zones matching a wide range of seismic hazard in Italy. The assessment showed the protocol be effective and ready for a wide dissemination.

Description: Published

Description: SE325

Description: 2TM. Divulgazione Scientifica

Description: JCR Journal

Description: In aree di vulcanismo attivo e recente, oltre all’emissione di vapore e gas dai crateri centrali, si possono verificare emissioni di gas dal suolo che vengono rilasciati in modo diffuso o in mofete, o ancora che si disciolgono in acquiferi superficiali. Generalmente il gas più abbondante (fino al 99 vol.%) è l’anidride carbonica (CO2), ma in alcuni casi può essere anche il metano (CH4). La CO2 è un gas incolore e inodore che tende ad accumularsi in depressioni o scantinati dove ristagna in assenza di vento. Respirare aria con una concentrazione di anidride carbonica maggiore di 8 vol.% può condurre all’incoscienza o alla morte. Un esempio di quello che potrebbe accadere, anche se si tratta di un caso estremo, è rappresentato dal tragico evento avvenuto presso il lago Nyos in Camerun (un lago ospitato in un cratere vulcanico). Durante la notte del 21 agosto 1986 le acque del lago, sature di CO2, si rovesciarono improvvisamente e per decompressione si liberò una enorme quantità di gas che scese lungo i fianchi del cratere fino a raggiungere la valle sottostante dove vi era un villaggio. La nube di CO2, silenziosa e inodore, colse nel sonno gli abitanti e uccise circa 1700 persone e circa 3000 capi di bestiame [Barberi et al., 1986]. Numerosi incidenti dovuti all’inalazione di gas vulcanici sono avvenuti in varie altre parti del mondo, in particolare in Italia, Giappone, Nuova Zelanda [Hansell and Oppenheimer, 2004; Durand and Wilson, 2005] e nelle Isole Azzorre (Portogallo) [Viveiros et al., 2015]. Anche in Italia, purtroppo sono avvenuti diversi incidenti letali dovuti ad inalazione di CO2; si ricorda ad esempio che alla fine degli anni ’80 due bambini persero la vita nell’isola di Vulcano [Baubron et al., 1990] e ancora nel complesso vulcanico dei Colli Albani due uomini persero la vita, il primo a Cava dei Selci (frazione di Marino) nel 2000 e il secondo a Lavinio nel 2011 [Carapezza et al., 2003; Barberi et al., 2019]. Sempre in provincia di Roma, numerosi casi di intossicazione da CO2, che hanno altresì comportato l’evacuazione temporanea di alcune abitazioni, sono avvenuti per blowout (emissione incontrollata) di gas da pozzi d’acqua [Barberi et al., 2007; Carapezza et al., 2020]. La Campania ospita due dei vulcani quiescenti considerati tra i più pericolosi al mondo proprio per l’alta densità di popolazione che vive nelle zone esposte al pericolo: il Vesuvio e i Campi Flegrei. Anche in queste aree vulcaniche si hanno emissioni di gas endogeni e falde d’acqua ricche in CO2 e in caso di riattivazione del vulcano c’è da aspettarsi anche un forte incremento del rilascio del gas endogeno [Barberi et al., 2005]. Al fine di far conoscere tale problematica alla popolazione, si è ritenuto opportuno di agire sui ragazzi e di farlo in modo stimolante e divertente attraverso un Videogioco che catturi la loro attenzione in modo da portarli a scoprire le soluzioni più adeguate da adottare per individuare/evitare/gestire i pericoli legati a quello che spesso viene definito anche “carburante delle eruzioni”, i gas vulcanici. Le attività che hanno portato alla realizzazione di questo lavoro (e nello specifico del videogioco) sono state svolte nell’ambito del Progetto Europeo RESPIRE – Radon rEal time monitoring System and proactive Indoor Remediation (LIFE16ENV/IT/000553) e con la collaborazione di un Tirocinante del Dipartimento di Ingegneria dell’Informazione ed Elettrica e Matematica Applicata dell’Università degli Studi di Salerno. Il lavoro è stato descritto e sintetizzato in questo Report attraverso varie sezioni. La prima in cui si descrive la problematica dei Gas Vulcanici e della loro pericolosità; l’importanza e i vantaggi derivati dall’utilizzo di un videogioco come strumento di apprendimento; l’obiettivo che il videogioco si prefigge di raggiungere. Una seconda sezione in cui, in prima istanza, si evidenzia l’importanza di sviluppare un videogioco a partire da un Motore Grafico che consente di tralasciare i dettagli hardware e software di basso livello e di concentrarsi maggiormente sull’interattività e sulle regole del gioco, e in seconda istanza si descrivono le caratteristiche principali del motore grafico alla base del gioco (RPG Maker MV).Una terza sezione in cui viene presentato il videogioco sviluppato denominato “GioGas”; nello specifico, la sua trama, l’interfaccia grafica che lo caratterizza e alcuni sui dettagli implementativi. Infine, una sezione in cui vengono descritti gli sviluppi futuri come ad esempio la divulgazione presso le scuole e in occasione di eventi, l’implementazione di una versione multiplayer del gioco al fine di aggiungere ulteriori elementi di stimolo e di coinvolgimento per lo studente.

Description: Published

Description: 6SR VULCANI – Servizi e ricerca per la società

Description: N/A or not JCR

Description: PGS1 is a new compact portable seismic station, designed at INGV OBS and Earth Lab, that is specifically intended for the deployment of dense arrays of seismographs on-shore. With its low cost, compact design, high data-quality and long battery life, PGS1 is a perfect solution for seismic monitoring networks. PGS1 design is based on a solid polypropylene suitcase, containing a complete data acquisition system, two battery packs and a photovoltaic panel. The new Earth Lab 5s medium-period seismic sensor is included. The whole system meets the IP67 standard requirements both in transport and in acquisition configuration. PGS1 is normally equipped with one battery pack, one more pack can be added inside the suitcase achieving 40 days of battery life. The station is equipped with a photovoltaic panel, useful to extend the deployment length. Inside the suitcase, there are compartments where to store the seismic sensor, the photovoltaic panel and all the cables. Therefore, the station is very easy to transport.

Description: Published

Description: SE105

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: JCR Journal

Description: Low field magnetic susceptibility and other rock magnetic analyses are applied to inspect the magnetic nature of solid residuals in snow samples collected in downtown Rome and in two Natural Parks in central Italy. Field emission scanning electron microscope and energy dispersive spectroscopy (FESEM-EDS) analyses are utilized to reveal the nature of Fe-rich particles and discriminate their anthropogenic origin. The results indicate that magnetite (Fe3O4) is the main magnetic carrier in almost all samples and that the variations in concentration are directly associated with local sources of particulate matter (PM) from anthropogenic pollution related to automotive circulation in both environments. Magnetic minerals of other provenance are found as accessories. The snow deposits revealed to be an efficient neutral tool for fine particle collections, also in environments characterized by different concentration and source of pollutants.

Description: Published

Description: GM215

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: JCR Journal

Description: The 1971 eruption represents a benchmark in the recent history of Etna volcano. From a volcanological point of view, this eruption was characterised by complex intrusive dynamics associated with significant ground deformation that induced the activation of the Moscarello seismogenic fault and the formation of a new summit crater: the Southeast Crater. At the same time, the 1971 event marks an important change in the eruptive style and composition of the magma towards products richer in K. It is no coincidence that, over the next fifty years, there would be an increase in the frequency of summit and flank eruptions and associated output rate. From an historical viewpoint, the eruptive event of 1971 was the first important flank eruption studied by the International Institute of Volcanology: the analysis of the scientific articles on this activity reveals a greater multidisciplinary content in the descriptions and explanations of volcanic activity. Particularly important were the collaborations of British and French research groups that, together with their Italian colleagues, succeeded in giving a complete picture of the eruption and describing the state of knowledge on the Sicilian volcano. The multidisciplinary methodology used to study this eruption is still valid today.

Description: Published

Description: VO543

Description: 1V. Storia eruttiva

Description: JCR Journal

Description: This study analyses the relationship between the pre- and protohistoric sites on the slopes of Etna and the volcanic products, as well as the diverse settlement strategies in the different periods of prehistory. New C14 dating from significant excavations, in addition to those known from other Etnean sites, were performed with the aim of validating the chronology of the sequence of the different phases. A substantial concordance of the archaeological data with the volcanological ones has been found. It has been observed that a consistent human presence on Etna appears from the Middle Neolithic (5500 BC), after the sequence of eruptive events that marked the end of the Ellittico volcano (13550 - 13050 BC) and the formation of the Valle del Bove, and the subsequent debris and alluvial events on the eastern flanks of the volcano (7250 - 3350 BC). Human presence intensifies between the Late-Final Copper Age and the Early Bronze Age (2800 - 1450 BC), due to improvement in subsistence techniques and to the large presence of soils on lava flows suitable for sheep farming. The most recent phases of the Bronze Age are poorly represented, probably because of the concentration of the population in larger agglomerations (Montevergine and S. Paolillo at Catania, the Historical Hill at Paternò). The explosive eruptions taking place in this period seem to have had less impact on the settlement choices and have not affected the development of the sites over time.

Description: Published

Description: VO542

Description: 1V. Storia eruttiva

Description: JCR Journal

Description: This special issue of Annals of Geophysics entitled: “When Volcanologists Meet Archaeologists and Other Disciplines: Relationships Between Eruptions and Human Communities” originates from a session (S13) of the Rittmann International Conference which took place in Catania on February 13th 2020, having as its main theme the history of volcanology and the impact of volcanic activity on humans. The twelve articles collected in this special issue reflect the aims and contents of the reports presented by some participants at this session of the Rittmann conference

Description: Published

Description: 6SR VULCANI – Servizi e ricerca per la società

Description: JCR Journal

Description: Published

Description: 6TM. Poli Museali

Description: The Western Ionian Sea is characterised by an active and diffuse seismicity, directly related to the convergence of the European and African Plates and by gravitational sinking and rollback of the oceanic lithosphere. In this area, the location of earthquakes is characterised by considerable uncertainties due to large azimuthal gaps, resulting in notable location errors. This problem was partially overcome with the use of data recorded by NEMO-SN1 seafloor observatory (October 2002 - February 2003; June 2012 - May 2013). We relocated 1130 crustal and sub-crustal earthquakes using land network and NEMO-SN1 data. As most events occurred on Mt. Etna, we focused on 358 earthquakes in the offshore area and near the coasts of Sicily and Calabria. The use of the combined land-marine networks has improved the earthquake locations in terms of azimuthal GAP, as well as in horizontal and vertical errors. The comparison between locations performed with and without NEMO-SN1 data shows that differences in latitude, longitude and depths are more evident in the Western Ionian Sea and in the coast of Sicily, where values of the differences over 5 km correspond to structural heterogeneities. The increased number of seismic stations deployed on land from 2003 to 2012 did not influence the location of events occurring offshore, where NEMO-SN1 continued to be the distinctive tool in the location process. Moreover, the new 73 focal mechanisms computed with P-wave polarities from NEMO-SN1 and land stations are in agreement with the regional structural model, showing a prevalent normal, normal/oblique, and strike-slip kinematics. The similarity of two new focal solutions with the mechanisms of the main shock and aftershock of the 1990 earthquake demonstrates that the seismic structures are still active and potentially dangerous. The P-wave travel time residual analysis confirms the activity along the main structural alignments. A single point of observation in the Ionian Sea can significantly improve the quality of locations, giving an opportunity to focus on the seismogenic structures responsible for the occurrence of medium-to-high magnitude earthquakes.

Description: Published

Description: Se655

Description: 1T. Struttura della Terra

Description: JCR Journal

Description: The 8 September 1905 Calabria earthquake is the seismic event for which the Italian Seismic Catalogue shows the highest instrumental magnitude of the whole dataset. However, the reported MS = 7.47 was calculated over only two stations, and leaves room for a revision. In this work I provide a new estimate of the surface-wave magnitude of the earthquake calculated over sixteen individual values of magnitude from seven different stations. The new estimate is MS = 7.10 ± 0.21, a value that is consistently lined up with other estimates provided by means of macroseismic or geological evidence. The novel estimate is stable despite alternative epicentral locations and different depths proposed for this event by several investigators. The net variation of almost half a unit magnitude implies a resizing of the seismogenic source of the event in the frame of the seismotectonics of the region, and highlights the strong need for a systematic revision of the instrumental magnitude estimates for several ‘historical’ earthquakes that occurred at the dawning of the instrumental seismology.

Description: Published

Description: SE658

Description: 4T. Sismicità dell'Italia

Description: JCR Journal

Description: Usually seismicity is intended as a natural phenomenon; yet the recording and interpretation of data are a human undertaking, historically conditioned. This research starts from the hypothesis that the decrease in Italian seismicity observed in the historical catalog [Rovida et al., 2021] for the central years of the twentieth century is due to the social and political conditioning that hindered its registration. This work, which focuses on the 1930s, with a brief excursion into previous years, presents part of the results obtained. In particular, the article deals with three earthquakes of which the data are substantially updated (Calabria, 7.03.1928; Alpi Noriche, 14.05.1930; Valli Giudicarie, 14.04.1931); then it presents an important replica of the strong Maiella earthquake, without macroseismic data in the catalog [Rovida et al., 2021], (Maiella, 23.11.1933); finally it considers a “forgotten” fifth earthquake (Southern Italy, 13.04.1938).

Description: Published

Description: 1-78

Description: 4T. Sismicità dell'Italia

Description: JCR Journal

Description: Le finalità del progetto sono quelle di realizzare un prototipo di ionosonda per sondaggi obliqui basato sul principio del radar ad onda continua modulata in frequenza, implementato tramite dispositivi programmabili innovativi che permettono di realizzare uno strumento più piccolo e trasportabile rispetto alle ionosonde classiche. La ionosonda SDR è un radar bistatico costituito da un trasmettitore, che può servire contemporaneamente diversi ricevitori situati in località differenti, e da uno o più ricevitori che possono sintonizzarsi su differenti trasmettitori che effettuano sondaggi ad orari differenti. I sondaggi obliqui permettono di mappare la ionosfera in varie parti del territorio per la verifica di modelli teorici della ionosfera e per studiare la possibilità di usare le variazioni locali del Contenuto Elettronico Totale (TEC) come segnale di possibili precursori di terremoti.

Description: Published

Description: 1-32

Description: 6IT. Osservatori non satellitari

Description: N/A or not JCR

Description: Muography represents a recent and innovative tool for investigating the interior of active volcanoes. However, when dealing with frequently erupting open-vent volcanoes such as Stromboli, any result should take into con- sideration the structural and morphology changes caused by the eruptive activity. This may cause either summit collapses by magma withdrawal, or morphology growth by the accumulations of a fallout from the explosive activity, or more often a combination of both. In this chapter, we present an integration of various techniques, comprising muography and digital elevation model reconstruction, together with GBInSAR ground deformation and volcano seismicity, to reconstruct the geometry of the shallow magma supply system of the volcano and its changes in time. We show how muography can display the interior of the volcano as well as its outer growth, being sensitive to all volume changes that occurred between the framed surface and the detector. This was discovered in Stromboli by comparing digital topography in the interval between 2010 and 2012, when the rapid growth of the volcano summit by the accumulation of ballistic products in the area between the crater zone and the muon detec- tor occurred. This deposit, together with the filling in of the graben-like depression, formed during the 2007 eruption, by fallout during the persistent explosive activity, contributed to generating a remarkable anomaly in the summit area of the volcano visualized by muography. In addition, the shallow feeding system of the volcano was surveyed by GBInSAR and seismicity, which allowed us to reconstruct its path up to a depth of a few hundred meters.

Description: Published

Description: 75-91

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

Description: The Istituto Nazionale di Geofisica e Vulcanologia (INGV) was born from the unification of public research institutions in the field of geophysics and volcanology. In the first twenty years from the foundation law of 1999, the INGV has seen a remarkable development, alternating moments of expansion, with significant increases in funding and number of employees, with long periods of stagnation. During these years the number of people hired with fixed-term contracts has grown, also to meet the needs of seismic and volcanic monitoring of the Italian territory, carried out on the basis of agreements with the Department of Civil Protection. After twenty years, it's time to outline a picture of the present situation and the evolutionary process that determined it. With this objective, the following analysis of the evolution of INGV was carried out in the period between its establishment and 2019, with reference to aspects such as the composition of the personnel, its distribution in the Sections, age, gender, role, career, with the aim of providing a tool for evaluating the progress made and planning future developments. The presence of a large number of precarious workers, distributed unevenly in territorial offices, for many years represented the main problem of the INGV, but not the only one. The contraction of the funding and the hiring freeze also slowed the development of the careers of researchers and other employers. The poor gender balance among the personnel, in particular among researchers, and the high average age represents further critical elements. The appropriate rebalancing of heterogeneities, aimed at maximum functionality and effective growth of the institute, should be the challenge for the next years. The future of INGV will depend on the choices that will be made today and the knowledge of the evolution of the institution until today is an essential element for proper programming.

Description: Published

Description: 1-92

Description: 3TM. Comunicazione

Description: JCR Journal

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 1-186

Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: 1TM. Formazione

Description: 2TM. Divulgazione Scientifica

Description: N/A or not JCR

Description: This contribution illustrates the state of the art on the development of the multiparametric network in Sicily in the last three years. This region is wellknown for the strong earthquakes (M〉6.5) which struck in historic time. However, the coverage of the seismic network developed in the last decades was not fully optimized to the need of the seismic surveillance. Since 2017, the group belonging to the National Earthquake Observatory (ONT) which operates in Sicily launched a developing plan of the preexisting seismic network in the framework of the project FISR “Sale Operative Integrate e Reti di Monitoraggio del futuro: l’INGV 2.0 (S.O.I.R.)”. Such update will end by the next years thanks to the project “GRINT Italian Research Infrastructure for Geosciences” in the framework of the “Programma Operativo Nazionale” (PON) of the Italian Ministry for the University and Research. This plan envisages both the upgrade of monitoring systems in the already existing nodes, and the integration of new nodes. The main objective is to build a multiparametric network which integrates the main seismic network, with the monitoring of other geophysical signals through the implementation of other sensors: accelerometers, geodetic GPS, radon detectors, and corner reflectors. We also illustrate the plan for the realization of a redundant network which could support the tasks of the main infrastructure in case of failure of the latter. Finally, we present some experimental urbanscale networks which in the future could support the main infrastructure.

Description: Published

Description: 1-40

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: JCR Journal

Description: The present paper describes the process of moving from a research study of most common vulnerable non-structural elements, to deliver solutions, tools and guidelines to improve understanding of and responsiveness to community concerns about seismic risk and non-structural elements. The observed damage to non-structural elements following recent earthquakes in Italy, Portugal and Iceland, were used for designing communication tools under the KnowRISK EU project for multi-stakeholders (students, business and citizens): the Practical Guide, the Students Short Guide, the KnowRISK Portfolio of Solutions, the Move, Protect and Secure video, the augmented reality apps, the maquettes, the students notebooks, videos, board games and hands-on tools. The philosophy behind these deliverables is that some risks, once identified, can be eliminated or reduced by informing people and suggesting preventive or emergency measures. These tools are devoted to improving the seismic performance of non-structural elements and to reduce the associated economic losses, loss of functionality, and potential threats to life safety. The rationale behind the selection of the information that people need to know for converting knowledge to more safety is discussed and a description of the transference of the findings of research to communication solutions is presented. The tools were planned following the engagement-model in risk communication to ensure that needs of communities and selected stakeholders were acknowledged, and that recipients are addressed in a way that appeals to them. Different media and communication channels such as print, television, online, face-to face communication and interviews were used for risk communication.

Description: This study was co-financed by the European Commission’s Humanitarian Aid and Civil Protection (Grant agreement ECHO/SUB/2015/718655/PREV28).

Description: Published

Description: SE322

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

Description: JCR Journal

Description: The lava platform and the three pyroclastic cones of Vulcanello constitute the northernmostvolcanic structure of the island of Vulcano (Aeolian Islands). The sandy isthmus connecting theplatform to the main island was definitively formed in the first half of the 1500s; before then,Vulcano and Vulcanello were two close but separate islands. For a long time, the interpretation ofthe sources of the II-I century BC, had considered the islet as built up about 2200 years ago. Thisbelief, which proliferated among naturalists from the 17th century, is not confirmed in the ancienttexts or even in the geographical documents of the time, which do not indicate the presence ofVulcanello as a new and stable island near Vulcano. The islet would only be mentioned at the dawnof the second millennium, and named in Arabic “Gabal’ al Burkān”, meaning Mount of Vulcano;shortly thereafter the toponym changed to the Latin “Insulam Vulcanelli” and then, towards the15th century, finally to Vulcanello.Since the creation of a volcanic island certainly occurred in the Aeolian Islands in the classical era,but traces of it were quickly lost, the most plausible hypothesis is that it was formed in the area ofthe current Vulcanello, to be subsequently erased by the sea. The shallow, flat seabed, likelyremaining as a result of sea abrasion, might have represented the morphological element on whichthe circular lava platform we know today was formed sometime between 950 and 1000 AD.

Description: Published

Description: VO548

Description: 1V. Storia eruttiva

Description: JCR Journal

Description: On November 20, 2019, an exercise was held at the National Institute of Geophysics and Volcanology (INGV) as part of the activities planned for preparing for seismic emergencies. The training was "tabletop" with the simulation of an earthquake with a magnitude greater than the threshold required for the activation of the intervention procedures, described in the "Protocol of the Authority for the management of seismic and tsunami emergencies and Establishment of the Crisis Unit”, the flow of actions that follow was verified. The exercise involved the entire INGV even if the Rome headquarters was the most involved, and it was the second of this type after that carried out in 2015 [Pondrelli et al., 2016]. Main motivation of this training was the analysis of the efficiency of the Organization Protocol, a document that for the first time at INGV codifies the actions of the Crisis Unit and of the Institute in general on the occurrence of seismic events and / or seismic sequences and / or tsunamis. The Protocol has been formalized on the basis of the numerous experiences that the Institute has supported over many years, to honour its vocation in the monitoring and seismic surveillance of the national territory [Margheriti et al., 2021].

Description: Published

Description: 1-50

Description: 2SR TERREMOTI - Gestione delle emergenze sismiche e da maremoto

Description: N/A or not JCR

Description: The influence of the Atlantic multidecadal variability (AMV) on the North Atlantic storm track and eddy-driven jet in the winter season is assessed via a coordinated analysis of idealized simulations with state-of-the-art coupled models. Data used are obtained from a multimodel ensemble of AMV± experiments conducted in the framework of the Decadal Climate Prediction Project component C. These experiments are performed by nudging the surface of the Atlantic Ocean to states defined by the superimposition of observed AMV± anomalies onto the model climatology. A robust extratropical response is found in the form of a wave train extending from the Pacific to the Nordic seas. In the warm phase of the AMV compared to the cold phase, the Atlantic storm track is typically contracted and less extended poleward and the low-level jet is shifted toward the equator in the eastern Atlantic. Despite some robust features, the picture of an uncertain and model-dependent response of the Atlantic jet emerges and we demonstrate a link between model bias and the character of the jet response.

Description: Published

Description: 347-360

Description: 4A. Oceanografia e clima

Description: JCR Journal

Description: Il mondo della Ricerca e dell ’Innovazione Tecnologica per sua natura è sempre in evoluzione, ed accompagnato da normative in materia di Sicurezza e Salute non sempre conosciute o applicate. La particolare enfasi data alla formazione nel quadro normativo riguardante la Sicurezza e Salute nei luoghi di lavoro, sia a livello nazionale che comunitario, dimostra e determina l’importanza attribuita a tale processo, non solo come mezzo elettivo per la diffusione della cultura della Sicurezza a tutti i livelli , ma anche, e soprattutto, come misura generale di tutela.

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 1-54

Description: 1TM. Formazione

Description: N/A or not JCR

Description: Within a fault governing model the characteristic scale length is one of the most relevant physical parameters because it accounts for the so–called fracture energy (density) of the system, its dynamics, the time during which the accumulated stress is released and the seismic waves are excited, the amount of slip developed during an instability event. Friction laboratory experiments reveal that it is not a material property, but that it changes with the sliding velocity. We propose two rather different analytical models to fit laboratory evidence and we incorporate them into a fault model able to simulate repeated earthquakes in the framework of various formulations of rate and state friction. We demonstrate that temporal variations of the scale length do not prevent the system to reach its limit cycle, but they systematically reduce the magnitude of the expected event (both in term of developed slip, and thus seismic moment, and released stress) and also reduce the inter–event time (recurrence interval). Depending on the friction model, the system can penetrate into the stable regime and can either continue the accelerating phase toward to failure or decelerate and abort instability.

Description: Published

Description: SE217

Description: 3T. Fisica dei terremoti e Sorgente Sismica

Description: JCR Journal

Description: The understanding of the ancient Earth’s Magnetic Field strength, or absolute paleointensity, is fundamental for several disciplines of Earth Sciences. Following the growing interest in this field in the last decades, the number of paleointensity studies has been increasing and the Paleomagnetic Laboratory of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome, Italy expanded the instrument park with a ASC TD48SC oven for paleomagnetic and paleointensity measurements. This manual represents an updated version of the original manual “Guida all’uso del forno ASC TD48SC per la stima della paleointensità assoluta con il metodo ThellierThellier modificato” [Di Chiara, 2014]. The aim is to provide a practical guide for paleointensity measurements, using the IZZIThellier experiment and the software Thellier_GUI for the processing of the geomagnetic field strength or paleointensity data.

Description: INGV

Description: Published

Description: 1-20

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: N/A or not JCR

Description: We describe the geochemical characteristics of groundwater samples collected in 23 water wells located on the northern margin of the Hyblean plateau (East Sicily). This area, mostly made of highly permeable carbonate rocks, is rich in low temperature (T 〈 50° C) hydrothermal groundwaters, distributed in an active sismogenetic zone, with several ENE-WSW-directed tectonic structures that drove magma to the surface during Upper Pliocene and Pleistocene. The chemical features suggest complex mixing between rainwater, CO2-rich groundwater, steam-heated groundwater and geothermal brines, as highlighted by Principal Component Analysis (PCA). Some parameters, however, indicate widespread pollution of the aquifers from human activities. Stable isotopes analysis confirms the meteoric origin of groundwater and supports the origin of dissolved CO2 mostly from mantle degassing through deep tectonic faults. Geothermometric estimates, mostly based on quartz and Saturation Indexes geothermometers, suggest minimum reservoir temperature between 100 and 120° C.

Description: Published

Description: HS438

Description: 1TR. Georisorse

Description: JCR Journal

Description: A ground magnetic study was performed on the northern upper flank of Mt. Etna to provide new insights into subsurface volcano-tectonic structures. The high resolution magnetic survey was focused on the main structures of Piano delle Concazze, a large flat area dominated by the North- East crater and bounded by the rim of the Valle del Leone depression and the extremity of the North-East Rift. More than 2,500 measurements were gathered with a sampling step of about 3 m covering an area of about 0.2 km2. The total-intensity anomaly field shows the presence of intense South-North aligned maxima related to shallow geological structures affecting this area. Filtering techniques and 2.5D modeling have been applied for the determination of the magnetic source parameters. In order to distinguish the near surface structure, filters of the vertical derivatives, Butterworth high-pass and the tilt derivative were used. The 3D Euler deconvolution has been applied to estimate the depth and the structural indices of the causative sources. The calculated structural indices, that express the geometrical nature of the source, are in agreement with forward modeling. They show that the area is mainly affected by subvertical normal fault and the estimated depth of magnetic sources ranges between 10 m and 40 m. Our total field magnetic survey shows that characteristic magnetic anomalies are related to fault zones in the Piano delle Concazze that are well consistent with the local tectonics. The subsurface structures that have been detected allowed to delineate the general structural framework of the area. In particular, it was possible to clarify that these structures seem to be not deep rooted and consequently they can hardly act as preferential pathways for magma ascent.

Description: Published

Description: PE108

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

Description: JCR Journal

Description: The traction evolution is a fundamental ingredient to model the dynamics of an earthquake rupture which ultimately controls, during the coseismic phase, the energy release, the stress redistribution and the consequent excitation of seismic waves. In the present paper we explore the use of the friction behavior derived from laboratory shear experiments performed on granular materials at low normal stress. We find that the rheological properties emerging from these laboratory experiments can not be described in terms of preexisting governing models already presented in literature; our results indicate that neither rate–and state–dependent friction laws nor nonlinear slip–dependent models, commonly adopted for modeling earthquake ruptures, are able to capture all the features of the experimental data. Then, by exploiting a novel numerical approach, we directly incorporate the laboratory data into a code to simulate the fully dynamic propagation of a 3–D slip failure. We demonstrate that the rheology of the granular material, imposed as fault boundary condition, is dynamically consistent. Indeed, it is able to reproduce the basic features of a crustal earthquake, spontaneously accelerating up to some terminal rupture speed, both sub– and supershear.

Description: Published

Description: SE441

Description: 3T. Fisica dei terremoti e Sorgente Sismica

Description: JCR Journal

Description: INGV

Description: Published

Description: 1-18

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: N/A or not JCR

Description: In the last decade, bottom-up strategies of risk education have raised importance, making seriousgames to become an alternative or complementary teaching tool for enhancing skills for acollaborative and adaptive response to social-ecological challenges. This study describes issues and challenges of serious games implemented within the framework oftwo European projects, namely UPStrat-MAFA (Urban Disaster Prevention Strategies usingMacroseismic Fields and FAult sources) and KnowRISK (Know your city, Reduce seISmic risKthrough non-structural elements); the goal is to instil in young people a proactive attitude towardsthe mitigation of seismic risk. The games were tested in some dissemination events focussed on fostering seismic riskpreparedness in students and improving good practices. We discuss the performance of our gameseven against more standard approaches to risk education. Our experience shows a rise of students’engagement compared to standard learning activities. The games were effective as students wereable to grasp the most relevant actions to reduce risk

Description: Published

Description: SE327

Description: 2TM. Divulgazione Scientifica

Description: JCR Journal

Description: A first combined absolute gravity and GNSS network of 5 stations distributed between Lazio, Umbria and Abruzzo regions, was realized in 2018 in order to lay the basics for a multidisciplinary approach to natural risk assessment in the area of Central Italy, affected by the 2009 and 2016 seismic activity. Up to now, two absolute gravity campaigns were carried out using the transportable Microg LaCoste FG5#238 and the portable A10#39 absolute gravimeters. The locations of gravimetric sites have been chosen indoor to allow optimal condition of measure; therefore, the heights of the indoor sites have been determined by joining the outdoor GNSS with classical topographic surveys. The good results obtained after the campaigns and data processing lay the foundations for a new multidisciplinary approach to study also seismogenetic areas. In this paper, we present the gravity and GNSS station monographs, together with the absolute gravity values and the coordinates resulting from the first field surveys.

Description: Published

Description: 1-26

Description: 4T. Sismicità dell'Italia

Description: JCR Journal

Description: Volcanic activity resumed during early Middle Ages times at Lipari following at least 6000 years of quiescence. This phenomenon occurred in a social context that had continuously developed from prehistoric times to the Roman age and was burdened by a demographic crisis that involved the archipelago between the 6th and 11th century AD. The rare archaeological records relating to the 6th - 11th centuries suggest abrupt changes in the population of the islands. The medieval sources are rich in religious and fantastic references to volcanic events linked to Lipari and Vulcano, testifying the uneasy condition for the human communities. This work concerns the resilience and adaptation of the communities to volcanic activity during the Late Middle Ages in Lipari. Starting from 1083 the Aeolian archipelago was involved in a repopulation program, implemented in 1095 by the Constitutum and organized by the Benedictine Monastery with the annexed S. Bartolomeo Cathedral on the castle. From the 13th century the volcanic phenomena, strictly limited to the northern sector of the island, did not interfere as previously with the anthropic activities. The Monastery will be enlarged in the Norman phase during the first half of the 12th century with the construction of the cloister. New historical documents relating to the 1264, report news of fires and land movements on Lipari. Recent age determinations obtained for the obsidian flow of Rocche Rosse at 1220 ± 30 AD (archaeomagnetic dating) and for an obsidian block of the Lami pyroclastic cone at 1243 ± 190 (fission-track dating) allow to define the age of the last phase of activity of the Monte Pilato-Lami-Rocche Rosse complex, and to associate it the events reported on 1264’s historical documents. This work makes in comparison volcanological, archaeological and historical dates and described an updated summary of one of the lesser known phases of the history of the archipelago. The main consequence of the medieval volcanic activity at Lipari caused a clear division of the territory with the population confined in the southeast quadrant, protected to the north by Serra and Monte Rosa which represented a natural orographic barrier.

Description: Published

Description: VO549

Description: 1V. Storia eruttiva

Description: JCR Journal

Description: Cenozoic climate changes have been linked to tectonic activity and variations in atmospheric CO2 concentrations. Here we present Miocene and Pliocene sensitivity experiments performed with the climate model COSMOS. The experiments contain changes with respect to paleogeography, ocean gateway configuration, and atmospheric CO2 concentrations, as well as a range of vertical mixing coefficients in the ocean. For the Mid-Miocene, we show that the impact of ocean mixing on surface temperature is comparable to the effect of the possible range in reconstructed CO2 concentrations. In combination with stronger vertical mixing, relatively moderate CO2-concentrations of 450 ppmv enable global mean surface, deep-water and meridional temperature characteristics representative of Mid-Miocene Climatic Optimum (MMCO) reconstructions. The Miocene climate shows a reduced meridional temperature gradient and reduced seasonality. In the case of enhanced mixing, surface and deep ocean temperatures show significant warming of up to 5-10°C and an Arctic temperature anomaly of more than 12°C. In the Pliocene simulations, the impact of vertical mixing and CO2 is less important for the deep ocean, which we interpret as a different sensitivity dependence on the background state and mixed layer dynamics. We find a significant reduction in surface albedo and effective emissivity for either a high level of atmospheric CO2 or increased vertical mixing. Our mixing sensitivity experiments provide a warm deep ocean via ocean heat uptake. We propose that the mixing hypothesis can be tested by reconstructions of the thermocline and seasonal paleoclimate data indicating a lower seasonality relative to today.

Description: As air temperatures rise and sea ice cover declines in the Arctic, permafrost coastal cliffs thaw more rapidly and wave energy rises. Thus, as the open water season continues to lengthen, climate change triggers a large part of the Arctic shoreline to become increasingly vulnerable to erosion. Arctic erosion supplies nutrient-laden and carbon-rich sediment into nearshore ecosystems. A retreating coastline also has consequences for residential, cultural, and industrial infrastructure. Despite its importance, erosion is currently neglected in global climate models, and existing physics-based numerical models of Arctic shoreline erosion are too complex and regionally-focused to be applied on a pan-Arctic scale. Here, we apply our simplified numerical erosion model, ArcticBeach v1.0, to the entire Arctic coastline. ArcticBeach v1.0 has previously been shown to simulate retreat rates at two sites that differ substantially in their main mechanisms of retreat (sub-aerial erosion/thaw slumping versus notch/block erosion). The model uses heat and sediment volume balances in order to predict horizontal cliff retreat and vertical erosion of a fronting beach. It contains an erosion module that uses empirical equations to estimate cross-shore sediment transport, coupled to a storm surge module forced by wind. We present Arctic maps of regional variation in trends in 2-meter air temperature, sea ice concentration, and wind speed.

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(2), (2020): e2019JC015400, doi:10.1029/2019JC015400.

Description: One of the foci of the Forum for Artic Modeling and Observational Synthesis (FAMOS) project is improving Arctic regional ice‐ocean models and understanding of physical processes regulating variability of Arctic environmental conditions based on synthesis of observations and model results. The Beaufort Gyre, centered in the Canada Basin of the Arctic Ocean, is an ideal phenomenon and natural laboratory for application of FAMOS modeling capabilities to resolve numerous scientific questions related to the origin and variability of this climatologic freshwater reservoir and flywheel of the Arctic Ocean. The unprecedented volume of data collected in this region is nearly optimal to describe the state and changes in the Beaufort Gyre environmental system at synoptic, seasonal, and interannual time scales. The in situ and remote sensing data characterizing ocean hydrography, sea surface heights, ice drift, concentration and thickness, ocean circulation, and biogeochemistry have been used for model calibration and validation or assimilated for historic reconstructions and establishing initial conditions for numerical predictions. This special collection of studies contributes time series of the Beaufort Gyre data; new methodologies in observing, modeling, and analysis; interpretation of measurements and model output; and discussions and findings that shed light on the mechanisms regulating Beaufort Gyre dynamics as it transitions to a new state under different climate forcing.

Description: We would like to thank all FAMOS participants (https://web.whoi.edu/famos/ and https://famosarctic.com/) and collaborators of the Beaufort Gyre Exploration project (https://www.whoi.edu/beaufortgyre) for their continued enthusiasm, creativity, and support during all stages of both projects. This research is supported by the National Science Foundation Office of Polar Programs (projects 1845877, 1719280, and 1604085). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Arctic dynamic topography/geostrophic currents data were provided by the Centre for Polar Observation and Modelling, University College London (www.cpom.ucl.ac.uk/dynamic_topography; Armitage et al. (2016, 2017). The other data used in this paper are available at the NCAR/NCEP (https://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.html), NSIDC (https://nsidc.org/), NSF's Arctic data center (https://arcticdata.io/; Keywords for data search are “Beaufort Gyre”, “Krishfield” or “Proshutinsky”), and WHOI Beaufort Gyre exploration website (www.whoi.edu/beaufortgyre).

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(4), (2020): e2019JC016006, doi:10.1029/2019JC016006.

Description: Equatorward flow of Middle Atlantic Bight (MAB) shelf waters meets poleward flowing South Atlantic Bight shelf waters over the continental shelf near Cape Hatteras, NC, leading to net export of shelf waters into the deep ocean. This export occurs in close proximity to the Gulf Stream, which separates from the continental margin near Cape Hatteras. Observations from sustained underwater glider surveys of the outer continental shelf and slope north of Cape Hatteras from spring 2017 to spring 2019 are used to examine the mean and variability of MAB shelf water export in the region. The 0.3 Sv (1 Sv = 106 m3 s−1) time‐mean export of MAB shelf water south of 37°N was dominated by discrete export events; 50% of export occurred during the 17% of the time during which transport was more than 1 standard deviation above the mean. These events typically occurred in late spring and summer of both years when equatorward flow into the region peaked. Export of MAB shelf water was correlated with equatorward flow into the region, which was itself correlated with the density gradient across the continental shelf break. Observations during specific time periods that capture extrema in MAB shelf water export are examined to highlight the variability in shelf‐deep ocean exchange scenarios in the Hatteras region. These include near‐surface export driven by hurricanes, subsurface export below the northern edge of the Gulf Stream, and a multi‐month near‐cessation of export.

Description: Patrick Deane at WHOI and the Instrument Development Group at the Scripps Institution of Oceanography were key to the success of the Spray glider operations. Mike Muglia, Trip Taylor, and Nick DeSimone at the East Carolina University Coastal Studies Institute (CSI) provided support for glider deployments and recoveries. WHOI Summer Student Fellow Devon Gaynes assisted with analysis related to 2017 hurricanes. Spray glider observations used here are available from http://spraydata.ucsd.edu and should be cited using the following DOIs: 10.21238/S8SPRAY2675 (Todd & Owens, 2016) and 10.21238/S8SPRAY0880 (Todd, 2020). Buoy winds are available from the National Data Buoy Center (https://www.ndbc.noaa.gov). SST imagery was obtained from the Mid‐Atlantic Regional Association Coastal Ocean Observing System (MARACOOS) THREDDS server (http://tds.maracoos.org/thredds/ARCHIVE-SST.html). Automated Tropical Cyclone Forecast System data are available online (https://ftp.nhc.noaa.gov/atcf/). PEACH was funded by the National Science Foundation (OCE‐1558521). Colormaps are from Thyng et al. (2016).

Description: 2020-09-17

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(5), (2020): e2020JC016123, doi:10.1029/2020JC016123.

Description: The processes underlying the strong Kuroshio encountering a cape at the southernmost tip of Taiwan are examined with satellite‐derived chlorophyll and temperature maps, a drifter trajectory, and realistic model simulations. The interaction spurs the formation of submesoscale cyclonic eddies that trap cold and high‐chlorophyll water and the formation of frontal waves between the free stream and the wake flow. An observed train of eddies, which have relative vorticity about one to four times the planetary vorticity (f), is shed from the recirculation that occurs in the immediate lee of the cape as a result of flow separation. These propagate downstream at a speed of 0.5–0.6 m s−1. Farther downstream, the corotation and merging of two or three adjacent eddies are common owing to the topography‐induced slowdown of eddy propagation farther downstream. It is found that the relative vorticity of a corotating system (1.2f) is 70% weaker than that of a single eddy due to the increase of eddy diameter from ~16 to ~33 km, in agreement with Kelvin's circulation theorem. The shedding period of the submesoscale eddies is strongly modulated by either diurnal or semidiurnal tidal flows, which typically reach 0.2–0.5 m s−1, whereas its intrinsic shedding period is insignificant. The frontal waves predominate in the horizontal free shear layer emitted from the cape, as well as a density front. Energetics analysis suggests that the wavy features result primarily from the growth of barotropic instability in the free shear layer, which may play a secondary process in the headland wake.

Description: Yu‐Hsin Cheng was supported by the CWB of Taiwan through Grant 1062076C. Ming‐Huei Chang was supported by the Ministry of Science and Technology of Taiwan (MOST) under Grants 103‐2611‐M‐002‐018, 105‐2611‐M‐002‐012, and 107‐2611‐M‐002‐015. Sen Jan was supported with MOST Grants 101‐2611‐M‐002‐018‐MY3, 103‐2611‐M‐002‐011, and 105‐2119‐M‐002‐042. Magdalena Andres was supported by the U.S. Office of Naval Research Grant N000141613069.

Description: 2020-10-23

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(6), (2020): e2020GC008957, doi:10.1029/2020GC008957.

Description: At the Galapagos triple junction in the equatorial Pacific Ocean, the Cocos‐Nazca spreading center does not meet the East Pacific Rise (EPR) but, instead, rifts into 0.4 Myr‐old lithosphere on the EPR flank. Westward propagation of Cocos‐Nazca spreading forms the V‐shaped Galapagos gore. Since ~1.4 Ma, opening at the active gore tip has been within the Cocos‐Galapagos microplate spreading regime. In this paper, bathymetry, magnetic, and gravity data collected over the first 400 km east of the gore tip are used to examine rifting of young lithosphere and transition to magmatic spreading segments. From inception, the axis shows structural segmentation consisting of rifted basins whose bounding faults eventually mark the gore edges. Rifting progresses to magmatic spreading over the first three segments (s1–s3), which open between Cocos‐Galapagos microplate at the presently slow rates of ~19–29 mm/year. Segments s4–s9 originated in the faster‐spreading (~48 mm/year) Cocos‐Nazca regime, and well‐defined magnetic anomalies and abyssal hill fabric close to the gore edges show the transition to full magmatic spreading was more rapid than at present time. Magnetic lineations show a 20% increase in the Cocos‐Nazca spreading rate after 1.1 Ma. The near‐axis Mantle Bouguer gravity anomaly decreases eastward and becomes more circular, suggesting mantle upwelling, increasing temperatures, and perhaps progression to a developed melt supply beneath segments. Westward propagation of individual Cocos‐Nazca segments is common with rates ranging between 12 and 54 mm/year. Segment lengths and lateral offsets between segments increase, in general, with distance from the tip of the gore.

Description: E. M. and H. S. are grateful to the National Science Foundation for funding this work and to InterRidge and the University of Leeds for providing support for a number of the international students and scholars who were able to participate on the cruise. We are also grateful for the extraordinary work of the Captain and crew of R/V Sally Ride , whose efficiency and good cheer made the cruise such a success. We thank M. Ligi and two anonymous reviewers for their comments which greatly improved the manuscript. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Description: 2020-11-11

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 22(3), (2021): e2020GC009472, https://doi.org/10.1029/2020GC009472.

Description: Carbonatite volcanism remains poorly understood compared to silicic volcanism due to the scarcity of carbonatite volcanoes worldwide and because volcanic H2O and CO2—major components in carbonatite volcanic systems—are not well preserved in the rock record. To further our understanding of carbonatite genesis, we utilize the non-traditional thallium (Tl) isotope system in Khanneshin carbonatites in Afghanistan. These carbonatites contain 250–30,000 ng/g Tl and have ε205Tl values (−4.6 to +4.6) that span much of the terrestrial igneous range. We observe that δ18OVSMOW (+8.6‰ to +23.5‰) correlates positively with δ13CVPDB (−4.6‰ to +3.5‰) and ε205Tl up to δ18O = 15‰. Rayleigh fractionation of calcite from an immiscible CO2-H2O fluid with a mantle-like starting composition can explain the δ18O and δ13C—but not ε205Tl—trends. Biotite fractionates Tl isotopes in other magmatic settings, so we hypothesize that a Tl-rich hydrous brine caused potassic metasomatism (i.e., biotite fenitization) of wall rock that increased the ε205Tl of the residual magma-fluid reservoir. Our results imply that, in carbonatitic volcanic systems, simultaneous igneous differentiation and potassic metasomatism increase ε205Tl, δ18O, δ13C, and light rare earth element concentrations in residual fluids. Our fractionation models suggest that the Tl isotopic compositions of the primary magmas were among the isotopically lightest (less than or equal to ε205Tl = −4.6) material derived from the mantle for which Tl isotopic constraints exist. If so, the ultimate source of Tl in Khanneshin lavas—and perhaps carbonatites elsewhere—may be recycled ocean crust.

Description: This project was supported by funding from Woods Hole Oceanographic Institution Independent Research & Development funds and the National Science Foundation (Award #1911699).

Description: 2021-07-27

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lattaud, J., Broder, L., Haghipour, N., Rickli, J., Giosan, L., & Eglinton, T., I. Influence of hydraulic connectivity on carbon burial efficiency in Mackenzie Delta lake sediments. Journal of Geophysical Research: Biogeosciences, 126(3), (2021): e2020JG006054, https://doi.org/10.1029/2020JG006054.

Description: The Arctic is undergoing accelerated changes in response to ongoing modifications to the climate system, and there is a need for local to regional scale records of past climate variability in order to put these changes into context. The Mackenzie Delta region in northern Canada is populated by numerous small shallow lakes. They are classified as no-, low-, and high-closure (NC, LC, and HC, respectively) lakes, reflecting varying degrees of connection to the river main stem, and have different sedimentation characteristics. This study examines sedimentological (mineral surface area, grain size), carbon isotopic (bulk and molecular-level) and inorganic isotopic (neodymium) characteristics of sediment cores from three lakes representing each class. We find that HC lake sediments exhibit strikingly different properties from the other lake sediments. Specifically, they are characterized by higher organic carbon loadings per unit mineral surface area and with relatively minor influence from allochthonous, petrogenic (rock-derived) organic carbon. In contrast, LC and NC lakes have the potential to record basin-scale climatic changes at a high resolution by virtue of enhanced detrital sedimentation. Overall the delta lakes have the capacity to bury about 2 MtC year−1, with little changes in the last 200 years. However, in the (near) future, an increased number of high closure lakes might change the carbon burial efficiency of the Mackenzie Delta as they seem to retain less carbon than NC and LC lakes.

Description: J. Lattaud was funded by a Rubicon grant (019.183EN.002) from NWO, Netherlands Organization for scientific research.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jackson, R. L., Gabric, A. J., Matrai, P. A., Woodhouse, M. T., Cropp, R., Jones, G. B., Deschaseaux, E. S. M., Omori, Y., McParland, E. L., Swan, H. B., & Tanimoto, H. Parameterizing the impact of seawater temperature and irradiance on dimethylsulfide (DMS) in the Great Barrier Reef and the contribution of coral reefs to the global sulfur cycle. Journal of Geophysical Research:Oceans, 126(3), (2021): e2020JC016783, https://doi.org/10.1029/2020JC016783.

Description: Biogenic emissions of dimethylsulfide (DMS) are an important source of sulfur to the atmosphere, with implications for aerosol formation and cloud albedo over the ocean. Natural aerosol sources constitute the largest uncertainty in estimates of aerosol radiative forcing and climate and thus, an improved understanding of DMS sources is needed. Coral reefs are strong point sources of DMS; however, this coral source of biogenic sulfur is not explicitly included in climatologies or in model simulations. Consequently, the role of coral reefs in local and regional climate remains uncertain. We aim to improve the representation of tropical coral reefs in DMS databases by calculating a climatology of seawater DMS concentration (DMSw) and sea-air flux in the Great Barrier Reef (GBR), Australia. DMSw is calculated from remotely sensed observations of sea surface temperature and photosynthetically active radiation using a multiple linear regression model derived from field observations of DMSw in the GBR. We estimate that coral reefs and lagoon waters in the GBR (∼347,000 km2) release 0.03–0.05 Tg yr−1 of DMS (0.02 Tg yr−1 of sulfur). Based on this estimate, global tropical coral reefs (∼600,000 km2) could emit 0.08 Tg yr−1 of DMS (0.04 Tg yr−1 of sulfur), with the potential to influence the local radiative balance.

Description: Australian Research Council. Grant Number: DP150101649 National Science Foundation (NSF). Grant Number: 1543450 Ministry of Education, Culture, Sports, Science and Technology Grants-in-Aid for Scientific Research. Grant Number: 23310016,16H02967,24241010,15H01732 Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid for Young Scientists. Grant Number: 17K12812

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(3), (2021): e2020JB021136, https://doi.org/10.1029/2020JB021136.

Description: The Geomagnetic Polarity Time Scale (GPTS) provides a basis for the geological timescale, quantifies geomagnetic field behavior, and gives a time framework for geologic studies. We build a revised Middle to Late Jurassic GPTS by using a new multiscale magnetic profile, combining sea surface, midwater, and autonomous underwater vehicle near-bottom magnetic anomaly data from the Hawaiian lineation set in the Pacific Jurassic Quiet Zone (JQZ). We correlate the new profile with a previously published contemporaneous magnetic sequence from the Japanese lineation set. We then establish geomagnetic polarity block models as a basis for our interpretation of the origin and nature of JQZ magnetic anomalies and a GPTS. A significant level of coherency between short-wavelength anomalies for both the Japanese and Hawaiian lineation magnetic anomaly sequences suggests the existence of a regionally coherent field during this period of rapid geomagnetic reversals. Our study implies the rapid onset of the Mesozoic Dipole Low from M42 through M39 and then a subsequent gradual recovery in field strength into the Cenozoic. The new GPTS, together with the Japanese sequence, extends the magnetic reversal history from M29 back in time to M44. We identify a zone of varying, difficult-to-correlate anomalies termed the Hawaiian Disturbed Zone, which is similar to the zone of low amplitude, difficult-to-correlate anomalies in the Japanese sequence termed the Low Amplitude Zone (LAZ). We suggest that the LAZ, bounded by M39–M41 isochrons, may in fact represent the core of what is more commonly known as the JQZ crust.

Description: This study is funded by National Science Foundation grants OCE-1029965 (Tominaga, Tivey, and Lizarralde) and OCE-1233000 (Tominaga and Tivey) and OCE-1029573 (Sager).

Description: 2021-07-21

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(1), (2020): e2019GL085455, doi:10.1029/2019GL085455.

Description: The meridional coherence, connectivity, and regional inhomogeneity in long‐term sea surface temperature (SST) variability over the Northwest Atlantic continental shelf and slope from 1982–2018 are investigated using observational data sets. A meridionally concurrent large SST warming trend is identified as the dominant signal over the length of the continental shelf and slope between Cape Hatteras in North Carolina and Cape Chidley, Newfoundland and Labrador, Canada. The linear trends are 0.37 ± 0.06 and 0.39 ± 0.06 °C/decade for the shelf and slope regions, respectively. These meridionally averaged SST time series over the shelf and slope are consistent with each other and across multiple longer observational data sets with records dating back to 1900. The coherence between the long‐term meridionally averaged time series over the shelf and slope and basin‐wide averaged SST in the North Atlantic implies approximately two thirds of the warming trend during 1982–2018 may be attributed to natural climate variability and the rest to externally forced change including anthropogenic warming.

Description: We are grateful to the Editor Dr. Kathleen Donohue and two anonymous reviewers. This work was supported by NOAA's Climate Program Office's Modeling, Analysis, Predictions, and Projections (MAPP) program (NA19OAR4320074). We acknowledge our participation in MAPP's Marine Prediction Task Force. The data of NOAA OISST used in this study are available at NOAA Earth System Research Laboratory (https://www.esrl.noaa.gov/psd/data/gridded/data.noaa.oisst.v2.highres.html). The HadISST data set is available at Met Office, Hadley Centre (https://www.metoffice.gov.uk/hadobs/hadisst/). The COBE SST and NOAA ERSST data sets are available at NOAA Earth System Research Laboratory's Physical Sciences Division (https://www.esrl.noaa.gov/psd/data/gridded/data.cobe.html; https://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.v5.html). The near‐surface air temperature is available at Global Historical Climatology Network‐Monthly Database (https://www.ncdc.noaa.gov/data‐access/land‐based‐station‐data/land‐based‐datasets/global‐historical‐climatology‐network‐monthly‐version‐4). The data of SSH are available at Copernicus Marine Environment Monitoring Service (http://marine.copernicus.eu/services‐portfolio/access‐to‐products/?option=com_csw&view=details&product_id=SEALEVEL_GLO_PHY_ L4_REP_OBSERVATIONS_008_047).

Description: 2020-07-06

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proshutinsky, A., Krishfield, R., Toole, J. M., Timmermans, M-L., Williams, W. J., Zimmermann, S., Yamamoto-Kawai, M., Armitage, T. W. K., Dukhovskoy, D., Golubeva, E., Manucharyan, G. E., Platov, G., Watanabe, E., Kikuchi, T., Nishino, S., Itoh, M., Kang, S-H., Cho, K-H., Tateyama, K., & Zhao, J. Analysis of the Beaufort Gyre freshwater content in 2003-2018. Journal of Geophysical Research-Oceans, 124(12), (2019): 9658-9689, doi:10.1029/2019JC015281.

Description: Hydrographic data collected from research cruises, bottom‐anchored moorings, drifting Ice‐Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997–2018) accompanied by sea ice melt, a wind‐forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year‐to‐year variability, or the more subtle interannual variations.

Description: National Science Foundation. Grant Numbers: PLR‐1302884,OPP‐1719280, and OPP‐1845877, PLR‐1303644 and OPP‐1756100, OPP‐1756100, PLR‐1303644, OPP‐1845877, OPP‐1719280, PLR‐1302884 Key Program of National Natural Science Foundation of China. Grant Number: 41330960 Global Change Research Program of China. Grant Number: 2015CB953900 Ministry of Education, Korea Japan Aerospace Exploration Agency (JAXA) /Earth Observation Research Center (EORC) Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) Stanback Postdoctoral Fellowship Russian Foundation for Basic Research. Grant Number: 17‐05‐00382 Presidium of Russian Academy of Sciences HYCOM NOPP. Grant Number: N00014‐15‐1‐2594 DOE. Grant Number: DE‐SC0014378 National Aeronautics and Space Administration Tokyo University of Marine Science and Technology Department of Fisheries and Oceans Canada Woods Hole Oceanographic Institution

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Catunda, M. C. A., Bahr, A., Kaboth-Bahr, S., Zhang, X., Foukal, N. P., & Friedrich, O. Subsurface heat channel drove sea surface warming in the high-latitude North Atlantic during the Mid-Pleistocene Transition. Geophysical Research Letters, 48(11), (2021): e2020GL091899, https://doi.org/10.1029/2020GL091899.

Description: The Mid-Pleistocene Transition (MPT, 1,200–600 ka) marks the rapid expansion of Northern Hemisphere (NH) continental ice sheets and stronger precession pacing of glacial/interglacial cyclicity. Here, we investigate the relationship between thermocline depth in the central North Atlantic, subsurface northward heat transport and the initiation of the 100-kyr cyclicity during the MPT. To reconstruct deep-thermocline temperatures, we generated a Mg/Ca-based temperature record of deep-dwelling (∼800 m) planktonic foraminifera from mid-latitude North Atlantic at Site U1313. This record shows phases of pronounced heat accumulation at subsurface levels during the mid-MPT glacial driven by increased outflow of the Mediterranean Sea. Concurrent warming of the subtropical thermocline and subpolar surface waters indicates enhanced (subsurface) inter-gyre transport of warm water to the subpolar North Atlantic, which provided moisture for ice-sheet growth. Precession-modulated variability in the northward transport of subtropical waters imprinted this orbital cyclicity into NH ice-sheets after Marine Isotope Stage 24.

Description: Catunda and A. Bahr were funded by DFG project BA 3809/8, O.F. by DFG project FR 2544/11. S. Kaboth-Bahr acknowledges an Open-Topic Post-Doc Grant from the University of Potsdam. X.Z. was funded via the Lanzhou University (project 225000–830006) and National Science Foundation of China (Grant 42075047). N.F. was funded by the NSF Grant 1756361. Open access funding enabled and organized by Projekt DEAL.

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 48(5), (2021): e2020GL091461, https://doi.org/10.1029/2020GL091461.

Description: We investigate how the near-surface chlorophyll (CHL)-a evolves in Gulf Stream (GS) warm-core rings (WCRs) and cold-core rings (CCRs) using multi-platform satellite observations. Averaged CHL anomaly (CHLA) within the rings exhibits both positive and negative linear trends during the evolution of the WCRs while negative trends dominate in CCRs. This difference is associated with a variety of physical processes occurring during the evolution process. Meanwhile, eddy-centric analysis reveals four spatial patterns of CHLA long-term trends, some of which highlights the importance of rings in shaping surface CHL. Short-term fluctuations of CHLA in WCRs and CCRs are closely correlated with mixed layer depth and sea surface temperature anomaly and highlight the complex interplay between multiple mechanisms. In addition, we find higher concentration CHL in some WCRs than that in CCRs during the same season, providing an alternative view of the characteristics of the surface ecosystem in Gulf Stream rings.

Description: This work was supported by the National Science Foundation Ocean Science Division under grant OCE-1558960. JN was supported by the Fundamental Research Funds for the Central Universities (Hohai University) under grant B200203005 and the China Scholarship Council.

Description: 2021-08-16

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(4), (2021): e2020JC016789, https://doi.org/10.1029/2020JC016789.

Description: Argo profiling floats and L-band passive microwave remote sensing have significantly improved the global sampling of sea surface salinity (SSS) in the past 15 years, allowing the study of the range of SSS seasonal variability using concurrent satellite and in situ platforms. Here, harmonic analysis was applied to four 0.25° satellite products and two 1° in situ products between 2016 and 2018 to determine seasonal harmonic patterns. The 0.25° World Ocean Atlas (WOA) version 2018 was referenced to help assess the harmonic patterns from a long-term perspective based on the 3-year period. The results show that annual harmonic is the most characteristic signal of the seasonal cycle, and semiannual harmonic is important in regions influenced by monsoon and major rivers. The percentage of the observed variance that can be explained by harmonic modes varies with products, with values ranging between 50% and 72% for annual harmonic and between 15% and 19% for semiannual harmonic. The large spread in the explained variance by the annual harmonic reflects the large disparity in nonseasonal variance (or noise) in the different products. Satellite products are capable of capturing sharp SSS features on meso- and frontal scales and the patterns agree well with the WOA 2018. These products are, however, subject to the impacts of radiometric noises and are algorithm dependent. The coarser-resolution in situ products may underrepresent the full range of high-frequency small scale SSS variability when data record is short, which may have enlarged the explained SSS variance by the annual harmonic.

Description: L. Yu was funded by NASA Ocean Salinity Science Team (OSST) activities through Grant 80NSSC18K1335. FMB was funded by the NASA OSST through Grant 80NSSC18K1322. E. P. Dinnat was funded by NASA through Grant 80NSSC18K1443. This research is carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Description: 2021-09-17

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schultz, C., Doney, S. C., Hauck, J., Kavanaugh, M. T., & Schofield, O. Modeling phytoplankton blooms and inorganic carbon responses to sea-ice variability in the West Antarctic Peninsula. Journal of Geophysical Research: Biogeosciences, 126(4), (2021): e2020JG006227, https://doi.org/10.1029/2020JG006227.

Description: The ocean coastal-shelf-slope ecosystem west of the Antarctic Peninsula (WAP) is a biologically productive region that could potentially act as a large sink of atmospheric carbon dioxide. The duration of the sea-ice season in the WAP shows large interannual variability. However, quantifying the mechanisms by which sea ice impacts biological productivity and surface dissolved inorganic carbon (DIC) remains a challenge due to the lack of data early in the phytoplankton growth season. In this study, we implemented a circulation, sea-ice, and biogeochemistry model (MITgcm-REcoM2) to study the effect of sea ice on phytoplankton blooms and surface DIC. Results were compared with satellite sea-ice and ocean color, and research ship surveys from the Palmer Long-Term Ecological Research (LTER) program. The simulations suggest that the annual sea-ice cycle has an important role in the seasonal DIC drawdown. In years of early sea-ice retreat, there is a longer growth season leading to larger seasonally integrated net primary production (NPP). Part of the biological uptake of DIC by phytoplankton, however, is counteracted by increased oceanic uptake of atmospheric CO2. Despite lower seasonal NPP, years of late sea-ice retreat show larger DIC drawdown, attributed to lower air-sea CO2 fluxes and increased dilution by sea-ice melt. The role of dissolved iron and iron limitation on WAP phytoplankton also remains a challenge due to the lack of data. The model results suggest sediments and glacial meltwater are the main sources in the coastal and shelf regions, with sediments being more influential in the northern coast.

Description: C. Schultz, S. C. Doney, M. T. Kavanaugh, and O. Schofield acknowledge support by the US National Science Foundation (Grant no. PLR-1440435), and C. Schultz and S. C. Doney acknowledge support from the University of Virginia. This research has also received funding from the Helmholtz Young Investigator Group Marine Carbon and Ecosystem Feedbacks in the Earth System (MarESys), Grant number VH-NG-1301.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Dzwonkowski, B., Fournier, S., Lockridge, G., Coogan, J., Liu, Z., & Park, K. Cascading weather events amplify the coastal thermal conditions prior to the shelf transit of Hurricane Sally (2020). Journal of Geophysical Research: Oceans, 126(12), (2021): e2021JC017957, https://doi.org/10.1029/2021JC017957.

Description: Changes in tropical cyclone intensity prior to landfall represent a significant risk to human life and coastal infrastructure. Such changes can be influenced by shelf water temperatures through their role in mediating heat exchange between the ocean and atmosphere. However, the evolution of shelf sea surface temperature during a storm is dependent on the initial thermal conditions of the water column, information that is often unavailable. Here, observational data from multiple monitoring stations and satellite sensors were used to identify the sequence of events that led to the development of storm-favorable thermal conditions in the Mississippi Bight prior to the transit of Hurricane Sally (2020), a storm that rapidly intensified over the shelf. The annual peak in depth-average temperature of 〉29°C that occurred prior to the arrival of Hurricane Sally was the result of two distinct warming periods caused by a cascade of weather events. The event sequence transitioned the system from below average to above average thermal conditions over a 25-day period. The transition was initiated with the passage of Hurricane Marco (2020), which mixed the upper water column, transferring heat downward and minimizing the cold bottom water reserved over the shelf. The subsequent reheating of the upper ocean by surface heat flux from the atmosphere, followed by downwelling winds, effectively elevated shelf-wide thermal conditions for the subsequent storm, Hurricane Sally. The coupling of climatological downwelling winds and warm sea surface temperature suggest regions with such characteristics are at an elevated risk for storm intensification over the shelf.

Description: his paper is a result of research funded by the National Oceanic and Atmospheric Administration's RESTORE Science Program under awards NA17NOS4510101 and NA19NOS4510194 to the University of South Alabama and Dauphin Island Sea Lab and by the NASA Physical Oceanography program under award 80NSSC21K0553 and WBS 281945.02.25.04.67 to the University of South Alabama and the Jet Propulsion Laboratory. A portion of this work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank the NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group for the Moderate-resolution Imaging Spectroradiometer (MODIS) Terra ocean color data; 2014 Reprocessing. NASA OB.DAAC, Greenbelt, MD, USA. 10.5067/AQUA/MODIS/MODIS_OC.2014.0.

Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 49, (2022): e2021GL096180, https://doi.org/10.1029/2021gl096180.

Description: In the subtropical gyres, phytoplankton rely on eddies for transporting nutrients from depth to the euphotic zone. But, what controls the rate of nutrient supply for new production? We show that vertical nutrient flux both depends on the vertical motion within the eddying flow and varies nonlinearly with the phytoplankton growth rate. Flux is maximized when the growth rate matches the inverse of the decorrelation timescale for vertical motion. Using a three-dimensional ocean model and a linear nutrient uptake model, we find that phytoplankton productivity is maximized for a growth rate of 1/3 day−1, which corresponds to the timescale of submesoscale dynamics. Variability in the frequency of vertical motion across different physical features of the flow favors phytoplankton production with different growth rates. Such a growth-transport feedback can generate diversity in the phytoplankton community structure at submesoscales and higher net productivity in the presence of community diversity.

Description: MAF and AM were funded by N00014-16-1-3130 (ONR) and MAF was also supported by the Martin Fellowship, MIT.

Description: 2022-07-20

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Grooms, I., Loose, N., Abernathey, R., Steinberg, J. M., Bachman, S. D., Marques, G., Guillaumin, A. P., & Yankovsky, E. Diffusion-Based smoothers for spatial filtering of gridded geophysical data. Journal of Advances in Modeling Earth Systems, 13(9), (2021): e2021MS002552, https://doi.org/10.1029/2021MS002552.

Description: We describe a new way to apply a spatial filter to gridded data from models or observations, focusing on low-pass filters. The new method is analogous to smoothing via diffusion, and its implementation requires only a discrete Laplacian operator appropriate to the data. The new method can approximate arbitrary filter shapes, including Gaussian filters, and can be extended to spatially varying and anisotropic filters. The new diffusion-based smoother's properties are illustrated with examples from ocean model data and ocean observational products. An open-source Python package implementing this algorithm, called gcm-filters, is currently under development.

Description: I.G. and N.L. are supported by NSF OCE 1912332. R.A. is supported by NSF OCE 1912325. J.S. is supported by NSF OCE 1912302. S.B. and G.M. are supported by NSF OCE 1912420. A.G. and E.Y. are supported by NSF GEO 1912357 and NOAA CVP NA19OAR4310364.

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(10),(2021): e2021JB022228, https://doi.org/10.1029/2021JB022228.

Description: Seafloor massive sulfide deposits form in remote environments, and the assessment of deposit size and composition through drilling is technically challenging and expensive. To aid the evaluation of the resource potential of seafloor massive sulfide deposits, three-dimensional inverse modeling of geophysical potential field data (magnetic and gravity) collected near the seafloor can be carried out to further enhance geologic models interpolated from sparse drilling. Here, we present inverse modeling results of magnetic and gravity data collected from the active mound at the Trans-Atlantic Geotraverse hydrothermal vent field, located at 26°08′N on the Mid-Atlantic Ridge, using autonomous underwater vehicle and submersible surveying. Both minimum-structure and surface geometry inverse modeling methods were utilized. Through deposit-scale magnetic modeling, the outer extent of a chloritized alteration zone within the basalt host rock below the mound was resolved, providing an indication of the angle of the rising hydrothermal fluid and the depth and volume of seawater/hydrothermal mixing zone. The thickness of the massive sulfide mound was determined by modeling the gravity data, enabling the tonnage of the mound to be estimated at 2.17 ± 0.44 Mt through this geophysics-based, noninvasive approach.

Description: The authors would like to thank the captain, crew, and scientific team from the 2016 R/V Meteor M127 and 1994 R/V Yokosuka MODE'94 cruises for all their work collecting the data modeled in this study. C. Galley is funded through an NSERC Discovery Grant and Memorial University's School of Graduate Studies Grant.

Description: 2022-03-29

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Beasley, C., Kender, S., Giosan, L., Bolton, C. T., Anand, P., Leng, M. J., Nilsson-Kerr, K., Ullmann, C. V., Hesselbo, S. P., & Littler, K. Evidence of a South Asian proto-monsoon during the Oligocene-Miocene transition. Paleoceanography and Paleoclimatology, 36(9), (2021): e2021PA004278, https://doi.org/10.1029/2021PA004278.

Description: The geological history of the South Asian monsoon (SAM) before the Pleistocene is not well-constrained, primarily due to a lack of available continuous sediment archives. Previous studies have noted an intensification of SAM precipitation and atmospheric circulation during the middle Miocene (∼14 Ma), but no records are available to test how the monsoon changed prior to this. In order to improve our understanding of monsoonal evolution, geochemical and sedimentological data were generated for the Oligocene-early Miocene (30–20 Ma) from Indian National Gas Hydrate Expedition 01 Site NGHP-01-01A in the eastern Arabian Sea, at 2,674 m water depth. We find the initial glaciation phase (23.7–23.0 Ma) of the Oligocene-Miocene transition (OMT) to be associated with an increase in water column ventilation and water mass mixing, suggesting an increase in winter monsoon type atmospheric circulation, possibly driven by a relative southward shift of the intertropical convergence zone. During the latter part of the OMT, or “deglaciation” phase (23.0–22.7 Ma), a long-term decrease in Mn (suggestive of deoxygenation), increase in Ti/Ca and dissolution of the biogenic carbonate fraction suggest an intensification of a proto-summer SAM system, characterized by the formation of an oxygen minimum zone in the eastern Arabian Sea and a relative increase of terrigenous material delivered by runoff to the site. With no evidence at this site for an active SAM prior to the OMT we suggest that changes in orbital parameters, as well as possibly changing Tethyan/Himalayan tectonics, caused this step change in the proto-monsoon system at this intermediate-depth site.

Description: This research forms part of a PhD study funded by the Natural Environment Research Council (NERC) Centre for Doctoral Training in Oil & Gas (grant number NE/M00578X/1) awarded to C. Beasley, and was also supported by a NERC National Environmental Isotope Facility Steering Committee grant (IP-1865-1118) awarded to S. Kender. L. Giosan acknowledges funding from USSP and WHOI and thanks colleagues from the NGHP-01 expedition. C. Ullmann acknowledges funding via NERC grant NE/N018508/1.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Goodkin, N. F., Samanta, D., Bolton, A., Ong, M. R., Hoang, P. K., Vo, S. T., Karnauskas, K. B., & Hughen, K. A. Natural and anthropogenic forcing of multi-decadal to centennial scale variability of sea surface temperature in the South China Sea. Paleoceanography and Paleoclimatology, 36(10), (2021): e2021PA004233, https://doi.org/10.1029/2021PA004233.

Description: Four hundred years of reconstructed sea surface temperatures (SSTs) from a coral located off the coast of Vietnam show significant multi-decadal to centennial-scale variability in wet and dry seasons. Wet and dry season SST co-vary significantly at multi-decadal timescales, and the Interdecadal Pacific Oscillation (IPO) explains the majority of variability in both seasons. A newly reconstructed wet season IPO index was compared to other IPO reconstructions, showing significant long-term agreement with varying amplitude of negative IPO signals based on geographic location. Dry season SST also correlates to sea level pressure anomalies and the East Asian Winter Monsoon, although with an inverse relationship from established interannual behavior, as previously seen with an ocean circulation proxy from the same coral. Centennial-scale variability in wet and dry season SST shows 300 years of near simultaneous changes, with an abrupt decoupling of the records around 1900, after which the dry season continues a long-term cooling trend while the wet season remains almost constant. Climate model simulations indicate greenhouse gases as the largest contributor to the decoupling of the wet and dry season SSTs and demonstrate increased heat advection to the western South China Sea in the wet season, potentially disrupting the covariance in seasonal SST.

Description: This research was supported by a Singapore National Research Fellowship to N.F. Goodkin (NRFF-2012-03) as administered by the Earth Observatory of Singapore and by a Singapore Ministry of Education Academic Research Fund Tier 2 award to N.F. Goodkin, K.A. Hughen, and K.B. Karnauskas (MOE-2016-T2-1-016). D. Samanta was partially supported by a Singapore Ministry of Education Tier 3 award (MOE2019-T3-1-004).

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 22(5), (2021): e2020GC009608, https://doi.org/10.1029/2020GC009608.

Description: Thallium (Tl) isotope ratios are an emerging tool that can be used to trace crustal recycling processes in arc lavas and ocean island basalts (OIBs). Thallium is a highly volatile metal that is enriched in volcanic fumaroles, but it is unknown whether degassing of Tl from subaerial lavas has a significant effect on their residual Tl isotope compositions. Here, we present Tl isotope and concentration data from degassing experiments that are best explained by Rayleigh kinetic isotope fractionation during Tl loss. Our data closely follow predicted isotope fractionation models in which TlCl is the primary degassed species and where Tl loss is controlled by diffusion and natural convection, consistent with the slow gas advection velocity utilized during our experiments. We calculate that degassing into air should be associated with a net Tl isotope fractionation factor of αnet = 0.99969 for diffusion and natural gas convection (low gas velocities) and αnet = 0.99955 for diffusion and forced gas convection (high gas velocities). We also show that lavas from three volcanoes in the Kamchatka arc exhibit Tl isotope and concentration patterns that plot in between the two different gas convection regimes, implying that degassing played an important role in controlling the observed Tl isotope compositions in these three volcanoes. Literature inspection of Tl isotope data for subaerial lavas reveals that the majority of these appear only minorly affected by degassing, although a few samples from both OIBs and arc volcanoes can be identified that likely experienced some Tl degassing.

Description: National Science Foundation (NSF). Grant Numbers: EAR 1829546

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 48(15), (2021): e2021GL092779, https://doi.org/10.1029/2021GL092779.

Description: Double diffusion refers to a variety of turbulent processes in which potential energy is released into kinetic energy, made possible in the ocean by the difference in molecular diffusivities between salinity and temperature. Here, we present a new method for estimating the kinetic energy dissipation rates forced by double-diffusive convection using temperature and salinity data alone. The method estimates the up-gradient diapycnal buoyancy flux associated with double diffusion, which is hypothesized to balance the dissipation rate. To calculate the temperature and salinity gradients on small scales we apply a canonical scaling for compensated thermohaline variance (or ‘spice’) on sub-measurement scales with a fixed buoyancy gradient. Our predicted dissipation rates compare favorably with microstructure measurements collected in the Chukchi Sea. Fine et al. (2018), https://doi.org/10.1175/jpo-d-18-0028.1, showed that dissipation rates provide good estimates for heat fluxes in this region. Finally, we show the method maintains predictive skill when applied to a sub-sampling of the Conductivity, Temperature, Depth (CTD) data.

Description: This work was supported by the Natural Environment Research Council (grant number NE/L002507/1).

Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(5), (2021): e2020JC017042, https://doi.org/10.1029/2020JC017042.

Description: In frontal zones, water masses that are tens of kilometers in extent with origins in the mixed layer can be identified in the pycnocline for days to months. Here, we explore the pathways and mechanisms of subduction, the process by which water from the surface mixed layer makes its way into the pycnocline, using a submesoscale-resolving numerical model of a mesoscale front. By identifying Lagrangian trajectories of water parcels that exit the mixed layer, we study the evolution of dynamical properties from a statistical standpoint. Velocity- and buoyancy-gradients increase as water parcels experience both mesoscale (geostrophic) and submesoscale (ageostrophic) frontogenesis and subduct beneath the mixed layer into the stratified pycnocline along isopycnals that outcrop in the mixed layer. Subduction is transient and occurs in coherent regions along the front, the spatial and temporal scales of which influence the scales of the subducted water masses in the pycnocline. An examination of specific subduction events reveals a range of submesoscale features that support subduction. Contrary to the forced submesoscale processes that sequester low potential vorticity (PV) anomalies in the interior, we find that PV can be elevated in subducting water masses. The rate of subduction is of similar magnitude to previous studies (∼100 m/year), but the Lagrangian evolution of properties on water parcels and pathways that are unraveled in this study emphasize the role of submesoscale dynamics coupled with mesoscale frontogenesis.

Description: This research was funded by the ONR CALYPSO DRI grant N00014-16-1-3130. MAF was partially funded by a Martin Fellowship from MIT.

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gawarkiewicz, G., Fratantoni, P., Bahr, F., & Ellertson, A. Increasing frequency of mid‐depth salinity maximum intrusions in the Middle Atlantic Bight. Journal of Geophysical Research: Oceans, 127(7), (2022): e2021JC018233, https://doi.org/10.1029./2021jc018233.

Description: Shelfbreak exchange processes have been studied extensively in the Middle Atlantic Bight. An important process occurring during stratified conditions is the Salinity Maximum Intrusion. These features are commonly observed at the depth of the seasonal pycnocline, and less frequently at the surface and bottom. Data collected from NOAA's National Marine Fisheries Service Ecosystem Monitoring program as well as data collected from the fishing industry in Rhode Island show that the middepth intrusions are now occurring much more frequently than was reported in a previous climatology of the intrusions (Lentz, 2003, https://doi.org/10.1029/2003JC001859). The intrusions have a greater salinity difference from ambient water and penetrate large distances shoreward of the shelf break relative to the earlier climatology. The longer term data from the Ecosystem Monitoring program indicates that the increase in frequency occurred in 2000, and thus may be linked to a recent regime shift in the annual formation rate of Warm Core Rings by the Gulf Stream. Given the increased frequency of these salty intrusions, it will be necessary to properly resolve this process in numerical simulations in order to account for salt budgets for the continental shelf and slope.

Description: Data collection for the Shelf Research Fleet and salary for G. Gawarkiewicz, F. Bahr, and A. Ellertson were provided by the van Beuren Charitable Foundation of Newport, RI. G. Gawarkiewicz, F. Bahr, and A. Ellertson were also supported in analysis of this data by NSF grant OCE-1851261.

Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, O., Lee, T., Piecuch, C., Fukumori, I., Fenty, I., Frederikse, T., Menemenlis, D., Ponte, R., & Zhang, H. Local and remote forcing of interannual sea‐level variability at Nantucket Island. Journal of Geophysical Research: Oceans, 127(6), (2022): e2021JC018275, https://doi.org/10.1029/2021jc018275.

Description: The relative contributions of local and remote wind stress and air-sea buoyancy forcing to sea-level variations along the East Coast of the United States are not well quantified, hindering the understanding of sea-level predictability there. Here, we use an adjoint sensitivity analysis together with an Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate to establish the causality of interannual variations in Nantucket dynamic sea level. Wind forcing explains 67% of the Nantucket interannual sea-level variance, while wind and buoyancy forcing together explain 97% of the variance. Wind stress contribution is near-local, primarily from the New England shelf northeast of Nantucket. We disprove a previous hypothesis about Labrador Sea wind stress being an important driver of Nantucket sea-level variations. Buoyancy forcing, as important as wind stress in some years, includes local contributions as well as remote contributions from the subpolar North Atlantic that influence Nantucket sea level a few years later. Our rigorous adjoint-based analysis corroborates previous correlation-based studies indicating that sea-level variations in the subpolar gyre and along the United States northeast coast can both be influenced by subpolar buoyancy forcing. Forward perturbation experiments further indicate remote buoyancy forcing affects Nantucket sea level mostly through slow advective processes, although coastally trapped waves can cause rapid Nantucket sea level response within a few weeks.

Description: This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). CGP was supported by NASA Sea Level Change Team awards 80NSSC20K1241 and 80NM0018D0004.

Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 46(16), (2019): 9851-9860, doi:10.1029/2019GL083726.

Description: Coral reef calcification is expected to decline due to climate change stressors such as ocean acidification and warming. Projections of future coral reef health are based on our understanding of the environmental drivers that affect calcification and dissolution. One such driver that may impact coral reef health is heterotrophy of oceanic‐sourced particulate organic matter, but its link to calcification has not been directly investigated in the field. In this study, we estimated net ecosystem calcification and oceanic particulate organic carbon (POCoc) uptake across the Kāne'ohe Bay barrier reef in Hawai'i. We show that higher rates of POCoc uptake correspond to greater net ecosystem calcification rates, even under low aragonite saturation states (Ωar). Hence, reductions in offshore productivity may negatively impact coral reefs by decreasing the food supply required to sustain calcification. Alternatively, coral reefs that receive ample inputs of POCoc may maintain higher calcification rates, despite a global decline in Ωar.

Description: Data needed for calculations are available in the supporting information. Additional data can be provided upon request directly from the corresponding author or accessed by links provided in the supporting information. The authors declare no competing financial interests. We thank Texas Sea Grant for providing partial funding for this project to A. Kealoha through the Grants‐In‐Aid of Graduate Research Program. We also thank the NOAA Nancy Foster Scholarship for PhD program funding to A. Kealoha and Texas A&M University for funds awarded to Shamberger that supported this work. This research was also supported by funding from National Science Foundation Grant OCE‐1538628 to Rappé. The Hawaii Institute of Marine Biology (particularly the Rappé Lab and Jason Jones), NOAA's Coral Reef Ecosystem Program, Connie Previti, Serena Smith, and Chris Maupin were instrumental in sample collection and data analysis.

Description: 2020-02-22

Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Atmospheres 124 (17-18), (2019): 9773-9795, doi: 10.1029/2018JD029933.

Description: National Aeronautics and Space Administration's Orbiting Carbon Observatory‐2 (OCO‐2) satellite provides observations of total column‐averaged CO2 mole fractions (XCO2 ) at high spatial resolution that may enable novel constraints on surface‐atmosphere carbon fluxes. Atmospheric inverse modeling provides an approach to optimize surface fluxes at regional scales, but the accuracy of the fluxes from inversion frameworks depends on key inputs, including spatially and temporally dense CO2 observations and reliable representations of atmospheric transport. Since XCO2 observations are sensitive to both synoptic and mesoscale variations within the free troposphere, horizontal atmospheric transport imparts substantial variations in these data and must be either resolved explicitly by the atmospheric transport model or accounted for within the error covariance budget provided to inverse frameworks. Here, we used geostatistical techniques to quantify the imprint of atmospheric transport in along‐track OCO‐2 soundings. We compare high‐pass‐filtered (〈250 km, spatial scales that primarily isolate mesoscale or finer‐scale variations) along‐track spatial variability in XCO2 and XH2O from OCO‐2 tracks to temporal synoptic and mesoscale variability from ground‐based XCO2 and XH2O observed by nearby Total Carbon Column Observing Network sites. Mesoscale atmospheric transport is found to be the primary driver of along‐track, high‐frequency variability for OCO‐2 XH2O. For XCO2 , both mesoscale transport variability and spatially coherent bias associated with other elements of the OCO‐2 retrieval state vector are important drivers of the along‐track variance budget.

Description: The authors thank the leadership and participants of the NASA OCO‐2 mission and acknowledge financial support from NASA Award NNX15AH13G. A.D. Torres also acknowledges support from the NASA Earth and Space Science Fellowship Award 80NSSC17K0382. We thank TCCON for providing observations. We thank A. Jacobson and the National Oceanographic and Atmospheric Administration Earth System Research Laboratory in Boulder, CO, for providing CarbonTracker CT2017 data, available online (http://carbontracker.noaa.gov). We thank S. Wofsy for providing HIPPO data, funded by the National Science Foundation and NOAA and available online (https://www.eol.ucar.edu/field_projects/hippo). The TCCON Principal Investigators acknowledge funding from their national funding organizations. TCCON data were obtained from the archive at the https://tccondata.org Web site. NARR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site (https://www.esrl.noaa.gov/psd/).

Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Planets 124, (2019): 3095-3118, doi: 10.1029/2019JE005937.

Description: We applied localized gravity/topography admittance and correlation analysis, as well as the Markov chain Monte Carlo method, to invert for loading and flexural parameters of 21 subregions on Mars with five distinct tectonic types. The loading styles of the five tectonic types are distinct: The surface and subsurface loading in the polar and plain regions can be assumed to be largely uncorrelated, in contrast to the correlated loading associated with the volcanic montes and Valles Marineris. For the impact basins, we consider the initial topographic depression and mantle plug before postimpact surface loading. Our analyses yield four main results: (1) The inverted effective lithospheric thickness (Te) is highly dependent on assumptions of loading type. (2) There is a trend of increasing Te from the Noachian southern highlands (20–60 km) to the Hesperian northern lowlands (〉90 km) and from the Hesperian Elysium Mons (〈55 km) to the Hesperian/Amazonian Olympus Mons (〉105 km). These Te estimates are consistent with the thermal states at the time of loading, corresponding to a global secular cooling history with decreasing heat flux. (3) Our analyses suggest high‐density basaltic surface loading at the volcanic montes and Isidis basin, in contrast to the low‐density sedimentary surface loading at the Utopia and Argyre basins. (4) We find some degree of correlation between the surface and subsurface loading for the northern polar cap and the northern plains, likely due to earlier, larger polar deposits and ancient buried features, respectively.

Description: The gravity model JGMRO120d and topography model MarsTopo719 used in this paper were retrieved from the Geosciences Node of NASA's Planetary Data System (http://pds‐geosciences.wustl.edu/mro/mro‐m‐rss‐5‐sdp‐v1/mrors_1xxx/data/shadr/) and from the SHTOOLS package (http://sourceforge.net/projects/shtools/), respectively. The MATLAB codes to reproduce the data analysis, parameter estimation, and key figures are available in a github repository (https://github.com/MinaDing/marslithosphere/tree/v1.0.0, DOI: 10.5281/zenodo.3530057). We are grateful to Mark Wieczorek and Frederik Simons for sharing relevant software online. We thank Ken Tanaka for providing a digital map of Mars chronographic ages. We thank Brandon Johnson for consultation on the loading processes of impact basins. We also thank Editor Laurent Montesi and Steven A. Hauck, as well as Patrick McGovern and anonymous reviewers for their invaluable feedbacks. This work was supported by National Natural Science Foundation of China (41806067, 41890813, 91628301 and U1606401), Key Laboratory of Ocean and Marginal Sea Geology, Chinese Academy of Sciences (OMG18‐02), Chinese Academy of Sciences (Y4SL021001, QYZDY‐SSW‐DQC005 and 133244KYSB20180029), Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0205), Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission (M.T.Z.), and National Science Foundation (EAR 1220280) and Henry Bigelow Chair for Excellence in Oceanography (J.L.).

Description: 2020-05-20

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spain, E. A., Johnson, S. C., Hutton, B., Whittaker, J. M., Lucieer, V., Watson, S. J., Fox, J. M., Lupton, J., Arculus, R., Bradney, A., & Coffin, M. F. Shallow seafloor gas emissions near Heard and McDonald Islands on the Kerguelen Plateau, Southern Indian Ocean. Earth and Space Science, 7(3), (2020): e2019EA000695, doi:10.1029/2019EA000695.

Description: Bubble emission mechanisms from submerged large igneous provinces remains enigmatic. The Kerguelen Plateau, a large igneous province in the southern Indian Ocean, has a long sustained history of active volcanism and glacial/interglacial cycles of sedimentation, both of which may cause seafloor bubble production. We present the results of hydroacoustic flare observations around the underexplored volcanically active Heard Island and McDonald Islands on the Central Kerguelen Plateau. Flares were observed with a split‐beam echosounder and characterized using multifrequency decibel differencing. Deep‐tow camera footage, water properties, water column δ3He, subbottom profile, and sediment δ13C and δ34S data were analyzed to consider flare mechanisms. Excess δ3He near McDonald Islands seeps, indicating mantle‐derived input, suggests proximal hydrothermal activity; McDonald Islands flares may thus indicate CO2, methane, and other minor gas bubbles associated with shallow diffuse hydrothermal venting. The Heard Island seep environment, with subbottom acoustic blanking in thick sediment, muted 3He signal, and δ13C and δ34S fractionation factors, suggest that Heard Island seeps may either be methane gas (possibly both shallow biogenic methane and deeper‐sourced thermogenic methane related to geothermal heat from onshore volcanism) or a combination of methane and CO2, such as seen in sediment‐hosted geothermal systems. These data provide the first evidence of submarine gas escape on the Central Kerguelen Plateau and expand our understanding of seafloor processes and carbon cycling in the data‐poor southern Indian Ocean. Extensive sedimentation of the Kerguelen Plateau and additional zones of submarine volcanic activity mean additional seeps or vents may lie outside the small survey area proximal to the islands.

Description: We thank the Australian Marine National Facility (MNF) for its support in the form of sea time on RV Investigator , support personnel, scientific equipment, and data management. We also thank the captain, crew, and fellow scientists of RV Investigator voyage IN2016_V01. We also thank specifically the following: T. Martin, F. Cooke, S. L. Sow, N. Bax, J. Ford, and F. Althaus, CSIRO (Commonwealth Scientific and Industrial Research Organisation); Echoview Software Pty. Ltd. (Hobart, Australia); C. Dietz and C. Cook, Central Science Laboratory, University of Tasmania; C. Wilkinson and T. Baumberger, National Oceanic and Atmospheric Administration; R. Carey, University of Tasmania; T. Holmes, Institute for Marine and Antarctic Studies, University of Tasmania; N. Polmear; and A. Post, Geoscience Australia. The overall science of the project is supported by Australian Antarctic Science Program (AASP) grant 4338. E.S.' PhD research is supported by the Australian Research Council's Special Research Initiative Antarctic Gateway Partnership (Project ID SR140300001) and by an Australian Government Research Training Program Scholarship. S.C.J. is supported by iCRAG under SFI, European Regional Development Fund, and industry partners, as well as ANZIC‐IODP. J.M.W. is supported by ARC grant DE140100376 and DP180102280. This is PMEL publication number 4910. All IN2016_V01 data and samples acquired on IN2016_V01 are made publicly available in accordance with MNF policy.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, J., Ma, Q., Wang, F., Lu, Y., & Pratt, L. J. Seasonal variation of the deep limb of the Pacific Meridional Overturning circulation at Yap-Mariana junction. Journal of Geophysical Research: Oceans, 125(7), (2020): e2019JC016017, doi:10.1029/2019JC016017.

Description: This study reveals the seasonal variability of the lower and upper deep branches of the Pacific Meridional Overturning Circulation (L‐PMOC and U‐PMOC) in the Yap‐Mariana Junction (YMJ) channel, a major gateway for deep flow into the western Pacific. On the western side of the YMJ channel, mooring observations in 2017 and in 1997 show the seasonal phase of the L‐PMOC at depths of 3,800–4,400 m: strong northward flow with speed exceeding 20 cm s−1 and lasting from December to next May and weak flow during the following 6 months. On the eastern side of the channel, mooring observations during 2014–2017 show two southward deep flows with broadly seasonal phases, one being the return flow of L‐PMOC below ~4,000 m and with the same phase of L‐PMOC but reduced magnitude. The second, shallower, southward deep flow corresponds to the U‐PMOC observed within 3,000–3,800 m and with opposite phase of L‐PMOC, that is, strong (weak) southward flow appearing during June–November (December–May). Seasonal variations of the L‐PMOC and U‐PMOC are accompanied by the seasonal intrusions of the Lower and Upper Circumpolar Waters (LCPW and UCPW) in lower and upper deep layers, which change the isopycnal structure and the deep currents in a way consistent with geostrophic balance.

Description: This study is supported by the National Natural Science Foundation of China (grants 91958204 and 41776022), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant XDA22000000), the Key Research Program of Frontier Sciences, CAS (grant QYZDB‐SSW‐SYS034). F. Wang thanks the support from the Scientific and Technological Innovation Project by Qingdao National Laboratory for Marine Science and Technology (grant 2016ASKJ12), the National Program on Global Change and Air‐Sea Interaction (grant GASI‐IPOVAI‐01‐01), and the National Natural Science Foundation of China (grants 41730534 and 41421005). L. Pratt gratefully acknowledges the support by NSF (grant OCE‐1657870). Jianing Wang and Qiang Ma contributed equally to this work.

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Black, E. E., Kienast, S. S., Lemaitre, N., Lam, P. J., Anderson, R. F., Planquette, H., Planchon, F., & Buesseler, K. O. Ironing out Fe residence time in the dynamic upper ocean. Global Biogeochemical Cycles, 34(9), (2020): e2020GB006592, doi:10.1029/2020GB006592.

Description: Although iron availability has been shown to limit ocean productivity and influence marine carbon cycling, the rates of processes driving iron's removal and retention in the upper ocean are poorly constrained. Using 234Th‐ and sediment‐trap data, most of which were collected through international GEOTRACES efforts, we perform an unprecedented observation‐based assessment of iron export from and residence time in the upper ocean. The majority of these new residence time estimates for total iron in the surface ocean (0–250 m) fall between 10 and 100 days. The upper ocean residence time of dissolved iron, on the other hand, varies and cycles on sub‐annual to annual timescales. Collectively, these residence times are shorter than previously thought, and the rates and timescales presented here will contribute to ongoing efforts to integrate iron into global biogeochemical models predicting climate and carbon dioxide sequestration in the ocean in the 21st century and beyond.

Description: We would like to thank S. Albani for providing the dust model results (Community Atmosphere Model, C4fn) and the three anonymous reviewers for their constructive comments. The U.S. GEOTRACES work was supported by the National Science Foundation (OCE‐1232669 and OCE‐1518110) and E. Black was also funded by a NASA Earth and Space Science Graduate Fellowship (NNX13AP31H) and the Ocean Frontier Institute. The GEOVIDE work was funded by the Flanders Research Foundation (G071512N), the Vrije Universiteit Brussel (SRP‐2), the French ANR Blanc GEOVIDE (ANR‐13‐BS06‐0014), ANR RPDOC BITMAP (ANR‐12‐PDOC‐0025‐01), IFREMER, CNRS‐INSU (programme LEFE), INSU OPTIMISP, and Labex‐Mer (ANR‐10‐LABX‐19).

Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Planets 125(9), (2020): e2019JE006209, doi:10.1029/2019JE006209

Description: Saturn's moon Enceladus has a global subsurface ocean and a porous rocky core in which water‐rock reactions likely occur; it is thus regarded as a potentially habitable environment. For icy moons like Enceladus, tidal heating is considered to be the main heating mechanism, which has generally been modeled using viscoelastic solid rheologies in existing studies. Here we provide a new framework for calculating tidal heating based on a poroviscoelastic model in which the porous solid and interstitial fluid deformation are coupled. We show that the total heating rate predicted for a poroviscoelastic core is significantly larger than that predicted using a classical viscoelastic model for intermediate to large (〉1014 Pa·s) rock viscosities. The periodic deformation of the porous rock matrix is accompanied by interstitial pore fluid flow, and the combined effects through viscous dissipation result in high heat fluxes particularly at the poles. The heat generated in the rock matrix is also enhanced due to the high compressibility of the porous matrix structure. For a sufficiently compressible core and high permeability, the total heat production can exceed 10 GW—a large fraction of the moon's total heat budget—without requiring unrealistically low solid viscosities. The partitioning of heating between rock and fluid constituents depends most sensitively on the viscosity of the rock matrix. As the core of Enceladus warms and weakens over time, pore fluid motion likely shifts from pressure‐driven local oscillations to buoyancy‐driven global hydrothermal convection, and the core transitions from fluid‐dominated to rock‐dominated heating.

Description: 2021-01-28

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Forsyth, J., Andres, M., & Gawarkiewicz, G. . Shelfreak jet structure and variability off New Jersey using ship of opportunity data from the CMV Oleander. Journal of Geophysical Research: Oceans, 125(9), (2020): e2020JC016455. doi:10.1029/2020JC016455.

Description: Repeat measurements of velocity and temperature profiles from the Container Motor Vessel (CMV) Oleander provide an unprecedented look into the variability on the New Jersey Shelf and upper continental slope. Here 1362 acoustic Doppler current profiler (ADCP) velocity sections collected between 1994 and 2018 are analyzed in both Eulerian and stream coordinate reference frames to characterize the mean structure of the Shelfbreak Jet, as well as its seasonal to decadal variability. The Eulerian mean Shelfbreak Jet has a maximum jet velocity of 0.12 m s−1. The maximum jet velocity peaks in April and May and reaches its minimum in July and August. In a stream coordinate framework, the jet is only identified in 61% of transects, and the mean stream coordinate Shelfbreak Jet has a maximum jet velocity of 0.32 m s−1. Evidence is found that Warm Core Rings, originating from the Gulf Stream arriving in the Slope Sea adjacent to the New Jersey Shelf, shift the Shelfbreak Jet onshore of its mean position or entirely shutdown the Shelfbreak Jet's flow. At interannual timescales, variability in the Shelfbreak Jet velocity is correlated with the temperature on the New Jersey Shelf 2 months later. When considered in a stream coordinate framework, Shelfbreak Jet have decreased over the time period considered in the study.

Description: J. F. and M. A. were supported by NSF OCE‐1634094 and OCE‐1924041. G. G was supported by NSF OCE‐1851261.