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  • Springer Nature  (17,698)
  • American Meteorological Society  (2,285)
  • AGU
  • Institut für Meereskunde
  • 2020-2023  (169)
  • 1935-1939  (19,852)
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  • 1
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    Thermokarst primes subsea permafrost degradation and coastal change (2020)
    AGU
    In:  EPIC3AGU Fall Meeting 2020, Virtual/Online, 2020-12-01-2020-12-17AGU
    Details
    Publication Date: 2022-03-11
    Description: Subsea permafrost forms when sea level rise from deglaciation or coastal erosion results in inundation of terrestrial permafrost. The response of permafrost to flooding in these settings will be determined by both ice-rich Pleistocene deposits and the thermokarst basins that thawed out during the Holocene. Thermokarst processes lower ground ice content, create partially drained and refrozen depressions (Alases) and thaw bulbs (taliks) beneath them, warm the ground, and can thaw the ground below sea level. We hypothesize that inundated Alases offshore with relatively lower ice content and higher porewater salinities in their sediments (possibly resulting from lagoon interaction) thaw faster than Yedoma terrain. To test this hypothesis, we estimated permafrost thaw rates offshore of the Bykovsky Peninsula in Tiksi Bay, northeastern Siberia using geoelectric surveys with floating electrodes. The surveys traversed a former undrained lagoon, drained and refrozen Alas deposits, and undisturbed Yedoma terrain at varying distances from shore. A continuous Yedoma-Alas-beach-lagoon survey was also carried out to obtain an indication of pre-inundation subsurface electrical resistivity. While the estimated degradation rates of the submerged Yedoma lies in the range of similar sites, and slows with increasing distance offshore, the Alas rates were more diverse and at least twice as fast within 125 m of the coastline. The latter is possibly due to saline lagoon water that infiltrated the Alas while it was still unfrozen. The ice-bearing permafrost depths of the former lagoon were generally the deepest of the terrain units, but displayed poor correlation with distance offshore. We attribute this to heterogeneous talik thickness upon the lagoon to sea transition, as well as permafrost aggradation processes beneath the spit. Given the prevalence of thermokarst basins and lakes along parts of the Arctic coastline, their effect on subsea permafrost degradation must be similarly prevalent. Remote sensing analyses suggest that 40% of lagoons wider than 500 m originated in thermokarst basins along the pan-Arctic coast. The more rapid degradation rates shown here suggest that low-ice content conduits for fluid flow may be more common than currently thought based on thermal modelling of subsea permafrost distribution.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
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    Thermokarst Landscape Evolution Recorded by n-Alkanes in a Deep Sediment Core from Bykovsky Peninsula, Northeast Siberia (2020)
    AGU
    In:  EPIC3AGU Fall Meeting 2020, Virtual/Online, 2020-12-01-2020-12-17AGU
    Details
    Publication Date: 2022-03-11
    Description: Warming of the Arctic triggers deep permafrost thaw, which has a strong impact on permafrost organic carbon (OC) storage. To identify the sedimentation history and organic matter (OM) characteristics of thermokarst-affected permafrost landscapes, we carried out an expedition in spring 2017 to the Bykovsky Peninsula. This is a remnant of a late Pleistocene accumulation plain on the Laptev Sea coast, northeastern Siberia. We retrieved a 31-m-long sediment core from underneath a thermokarst lake (water depth: 5.1 m) and analyzed the sediments for n-alkanes, total organic carbon content (TOC) and grain size. From the bottom upwards, the core contained 3 m of frozen sediments from underneath the thaw bulb (Unit I: 36.6-33 m), 25 m of unfrozen Yedoma (taberal) sediments (Unit II: 33-18 m, Unit III: 18-10 m) and 4 m of unfrozen lake sediments (Unit IV: 10-5.1 m). Unit I contained coarsest sediments and rounded pebbles, which point to a strong fluvial influence. Here, we found the highest TOC values (17.8 wt%) and drift wood (organic remains up to 4 cm in size). The dominant mid-chains n-alkanes n-C23 and n-C25 and a high aquatic plant n-alkane proxy Paq (median: 0.65) suggest the growth of submerged/floating macrophytes. With a value of 2.2, the odd-over-even predominance (OEP) is lowest in Unit I. Unit II has a lower relative distribution of the midchain n-alkanes, which suggests the vegetation was likely emergent rather than submerged (median Paq: 0.44). This indicates the onset of Yedoma formation and low-centered polygon development. In the finer sediments of Unit III, the Paq further decreases (median: 0.32) and n-C31 becomes more important, indicating the transition to a drier, grass dominated environment. The thermokarst lake (Unit IV) formed about 8 cal ka BP, indicated by a peat layer. The OM in Unit IV is fresh (median OEP: 8.4) and has the highest n-alkane concentration (20.8 µg g-1 sediment). In this study, we show that thermokarst formation has a potential of mobilizing a large OC pool to tens of meters deep: even though the OM in the sediments below the thaw bulb is furthest degraded, still a substantial amount of OC is stored here. The study of n-alkanes is very useful in identifying OM source and degradability and will help to improve OM mobilization estimates in thawing permafrost by investigating the molecular lipid structure.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Latitudinal structure of the meridional overturning circulation variability on interannual to decadal time scales in the North Atlantic Ocean (2020)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(9), (2020): 3845-3862, doi:10.1175/JCLI-D-19-0215.1.
    Description: The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.
    Description: The authors gratefully acknowledge support from the Physical Oceanography Program of the U.S. National Science Foundation (Awards OCE-1756143 and OCE-1537136) and the Climate Program Office of the National Oceanic and Atmospheric Administration (Award NA15OAR4310088). Gratitude is extended to Claus Böning and Arne Biastoch who shared ORCA025 output. S. Zou thanks F. Li, M. Buckley, and L. Li for helpful discussions. We also thank three anonymous reviewers for helpful suggestions.
    Keywords: Deep convection ; Ocean circulation ; Thermocline circulation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Resource partitioning of phytoplankton metabolites that support bacterial heterotrophy (2020)
    Springer Nature
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ferrer-González, F. X., Widner, B., Holderman, N. R., Glushka, J., Edison, A. S., Kujawinski, E. B., & Moran, M. A. Resource partitioning of phytoplankton metabolites that support bacterial heterotrophy. ISME Journal, (2020), doi:10.1038/s41396-020-00811-y.
    Description: The communities of bacteria that assemble around marine microphytoplankton are predictably dominated by Rhodobacterales, Flavobacteriales, and families within the Gammaproteobacteria. Yet whether this consistent ecological pattern reflects the result of resource-based niche partitioning or resource competition requires better knowledge of the metabolites linking microbial autotrophs and heterotrophs in the surface ocean. We characterized molecules targeted for uptake by three heterotrophic bacteria individually co-cultured with a marine diatom using two strategies that vetted the exometabolite pool for biological relevance by means of bacterial activity assays: expression of diagnostic genes and net drawdown of exometabolites, the latter detected with mass spectrometry and nuclear magnetic resonance using novel sample preparation approaches. Of the more than 36 organic molecules with evidence of bacterial uptake, 53% contained nitrogen (including nucleosides and amino acids), 11% were organic sulfur compounds (including dihydroxypropanesulfonate and dimethysulfoniopropionate), and 28% were components of polysaccharides (including chrysolaminarin, chitin, and alginate). Overlap in phytoplankton-derived metabolite use by bacteria in the absence of competition was low, and only guanosine, proline, and N-acetyl-d-glucosamine were predicted to be used by all three. Exometabolite uptake pattern points to a key role for ecological resource partitioning in the assembly marine bacterial communities transforming recent photosynthate.
    Description: This work was supported by grants from the Gordon and Betty Moore Foundation (5503) and the National Science Foundation (IOS-1656311) to MAM, ASE, and EBK, and by the Simons Foundation grant 542391 to MAM within the Principles of Microbial Ecosystems (PriME) Collaborative.
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Importance of Orography for Greenland cloud and melt response to atmospheric blocking (2020)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Hahn, L. C., Storelvmo, T., Hofer, S., Parfitt, R., & Ummenhofer, C. C. Importance of Orography for Greenland cloud and melt response to atmospheric blocking. Journal of Climate, 33(10), (2020): 4187-4206, doi:10.1175/JCLI-D-19-0527.1.
    Description: More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet.
    Description: This research was supported by the Woods Hole Oceanographic Institution Summer Student Fellow program, by the U.S. National Science Foundation under AGS-1355339 to C.C.U., and by the European Research Council through Grant 758005.
    Keywords: Ice sheets ; Blocking ; Cloud cover ; Topographic effects ; Climate change ; Climate variability
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Exploring Employee Perceptions towards Smart Working during the COVID-19 Pandemic: a Comparative Analysis of Two Italian Public Research Organizations (2021)
    Springer Nature
    Details
    Publication Date: 2022-03-16
    Description: Of all the socio-economic changes caused by the Covid-19 pandemic, the disruption to workforce organizations will probably leave the largest indelible mark. The way work will be organized in the future will be closely linked to the experience of work-ing under the same institution’s response to the pandemic. This paper aims to fill the gap in knowledge about smart working (SW) in public organizations, with a focus on the experience of the employees of two Italian research organizations, CNR and INGV. Analysing primary data, it explored and assessed how SW had been experi-enced following the implementation of governmental measures aimed at limiting the spread of COVID-19
    Description: Published
    Description: 815–833
    Description: 2TM. Divulgazione Scientifica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Combining audio and visual displays to highlight temporal and spatial seismic patterns (2021)
    Springer Nature
    Details
    Publication Date: 2022-03-16
    Description: Data visualization, and to a lesser extent data sonification, are classic tools to the scientific community. However, these two approaches are very rarely combined, although they are highly complementary: our visual system is good at recognizing spatial patterns, whereas our auditory system is better tuned for temporal patterns. In this article, data representation methods are proposed that combine visualization, sonification, and spatial audio techniques, in order to optimize the user’s perception of spatial and temporal patterns in a single display, to increase the feeling of immersion, and to take advantage of multimodal integration mechanisms. Three seismic data sets are used to illustrate the methods, covering different physical phenomena, time scales, spatial distributions, and spatio-temporal dynamics. The methods are adapted to the specificities of each data set, and to the amount of information that the designer wants to display. This leads to further developments, namely the use of audification with two time scales, the switch from pure audification to time-modulated noise, and the switch from pure audification to sonic icons. First user feedback from live demonstrations indicates that the methods presented in this article seem to enhance the perception of spatio-temporal patterns, which is a key parameter to the understanding of seismically active systems, and a step towards apprehending the processes that drive this activity.
    Description: Published
    Description: 125–142
    Description: 7T. Variazioni delle caratteristiche crostali e "precursori"
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Impacts of Arctic Sea Ice on Cold Season Atmospheric Variability and Trends Estimated from Observations and a Multi-model Large Ensemble (2022)
    American Meteorological Society
    Details
    Publication Date: 2022-03-01
    Description: To examine the atmospheric responses to Arctic sea ice variability in the Northern Hemisphere cold season (from October to the following March), this study uses a coordinated set of large-ensemble experiments of nine atmospheric general circulation models (AGCMs) forced with observed daily varying sea ice, sea surface temperature, and radiative forcings prescribed during the 1979–2014 period, together with a parallel set of experiments where Arctic sea ice is substituted by its climatology. The simulations of the former set reproduce the near-surface temperature trends in reanalysis data, with similar amplitude, and their multimodel ensemble mean (MMEM) shows decreasing sea level pressure over much of the polar cap and Eurasia in boreal autumn. The MMEM difference between the two experiments allows isolating the effects of Arctic sea ice loss, which explain a large portion of the Arctic warming trends in the lower troposphere and drive a small but statistically significant weakening of the wintertime Arctic Oscillation. The observed interannual covariability between sea ice extent in the Barents–Kara Seas and lagged atmospheric circulation is distinguished from the effects of confounding factors based on multiple regression, and quantitatively compared to the covariability in MMEMs. The interannual sea ice decline followed by a negative North Atlantic Oscillation–like anomaly found in observations is also seen in the MMEM differences, with consistent spatial structure but much smaller amplitude. This result suggests that the sea ice impacts on trends and interannual atmospheric variability simulated by AGCMs could be underestimated, but caution is needed because internal atmospheric variability may have affected the observed relationship.
    Description: Published
    Description: 8419–8443
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Arctic ; Sea ice ; Atmospheric circulation ; Climate models ; 01.01. Atmosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Structure of the upper mantle under the Antarctic Plate from surface wave tomography (2021)
    AGU
    Details
    Publication Date: 2021-12-06
    Description: We have analyzed surface wave data for 245 events occurring in Antarctica and surrounding oceans during years 1991-1999. We first apply dispersion analysis to the fundamental mode of Rayleigh waves for periods ranging from 20 to 150 sec. We then invert path-averaged dispersion curves to obtain 2D maps of group velocity for different periods, represented by splines on a grid with 250 km spacing, with considerably more detail than that achieved by global models. We finally use group velocity maps in a nonlinear inversion for the regional 3D υSV structure of the upper mantle. The resulting model shows thick continental roots under East Antarctica, reaching depths below 200 km; low velocities under oceanic ridges, mostly confined to the upper 150 km; and a slow area under the Ross Sea volcanic centres, extending all the way down to 200 km, beyond which our data loose resolving power.
    Description: Published
    Description: 4395-4398
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Looking inside mt. vesuvius (2021)
    AGU
    Details
    Publication Date: 2021-12-15
    Description: Italy's Mt.Vesuvius has been slumbering for a long time, but its silence could preface an eruption with potentially disastrous ef­fects for 600,000 people living on the vol­cano's slopes. To assess the scenario of the next eruption, the National Group of Vol-canology (GNV) of the Italian National Coun­cil of Researches (CNR) has fostered research aimed at mitigating eruption risk to the densely populated area. In this framework, researchers have gathered high-resolution seismic tomography data to better under­stand the internal structure of Mt. Vesuvius. The experiments were carried out during the last 4 years. The data will be used in three-dimen­sional modeling of the structure of Mt. Vesu­vius and underlying upper crust. Seismic velocities and attenuation and density con­trasts will be calculated, with special empha­sis on the delineation of significant magma reservoirs of more than 1 km in diameter. In modeling Mt. Vesuvius, tools are being devel­oped for using seismogram information to ob­tain high-quality seismic imaging of heterogeneous structures such as volcanoes
    Description: Published
    Description: 229-230, 232
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: N/A or not JCR
    Keywords: Tomography
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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