Angot, H., Magand, O., Helmig, D., Ricaud, P., Quennehen, B., Gallée, H., Del Guasta, M., Sprovieri, F., Pirrone, N., Savarino, J., Dommergue, A.. (2016). New insights into the atmospheric mercury cycling in central Antarctica and implications on a continental scale. Atmospheric chemistry and physics, 16(13), 8249–8264.
Abstract: Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75°06′ S, 123°20′ E, 3220 m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique data set shows evidence of an intense oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere in this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air–snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30 % decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24 h darkness). This phenomenon has not been reported elsewhere and possibly results from the dry deposition of Hg(0) onto the snowpack. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury on a continental scale.
Programme: 1028
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A. Haned, E. Stutzmann, M. Schimmel, S. Kiselev, A. Davaille and A. Yelles-Chaouche. (2016). Global tomography using seismic hum. Geophysical journal international, 204(2).
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Blanchard P., Lauzeral C., Chamaillé-Jammes S., Yoccoz N.G., Pontier D. . (2016). Analyzing the proximity to cover in a landscape of fear: a new approach applied to fine-scale habitat use by rabbits facing feral cat predation on Kerguelen archipelago. Peerj, 4, e1769.
Abstract: Although proximity to cover has been routinely considered as an explanatory variable in studies investigating prey behavioral adjustments to predation pressure, the way it shapes risk perception still remains equivocal. This paradox arises from both the ambivalent nature of cover as potentially both obstructive and protective, making its impact on risk perception complex and context-dependent, and from the choice of the proxy used to measure proximity to cover in the field, which leads to an incomplete picture of the landscape of fear experienced by the prey. Here, we study a simple predator-prey-habitat system, i.e., rabbits Oryctolagus cuniculus facing feral cat Felis catus predation on Kerguelen archipelago. We assess how cover shapes risk perception in prey and develop an easily implementable field method to improve the estimation of proximity to cover. In contrast to protocols considering the “distance to nearest cover”, we focus on the overall “area to cover”. We show that fine-scale habitat use by rabbits is clearly related to our measure, in accordance with our hypothesis of higher risk in patches with smaller area to cover in this predator-prey-habitat system. In contrast, classical measures of proximity to cover are not retained in the best predictive models of habitat use. The use of this new approach, together with a more in-depth consideration of contrasting properties of cover, could help to better understand the role of this complex yet decisive parameter for predator-prey ecology.
Programme: 279
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Bourriquen M., Baltzer A., Mercier D., Fournier J., Pérez L., Haquin S., Bernard E., Jensen M.. (2016). Coastal evolution and sedimentary mobility of Brøgger Peninsula, north-west Spitsbergen. Polar biology, .
Abstract: Since the end of the Little Ice Age (LIA), Svalbard glaciers have undergone a net retreat in response to changing meteorological conditions. Located between 76°N and 80°N, western Spitsbergen has seen a climatic transition from a glacial to a paraglacial system. On the northern shore of the Brøgger Peninsula (northwest Spitsbergen), the average temperature increased by 3 °C between 1965 and 2015, and cold-based valley glaciers have retreated more than 1 km from their LIA limits. This rapid deglaciation has exposed large areas of glacigenic sediments being easily reworked by runoff. This has led to the formation of extensive glacier-river delta systems and coastal progradation. Post-LIA coastal progradation and formation of new landforms in Kongsfjorden have been controlled predominantly by substantial availability of glacial sediment. A combination of aerial photographic and field data has been employed to estimate the post-LIA evolution of coastal sandur deltas and their submarine parts (named here “prodeltas”). The data set reveals that delta shoreline advance could have reached around 5 m/year. between 1966 and 1990 for the most energetic delta of Austre Lovenbreen, and around 4 m/year between 2011 and 2014 for the most energetic delta of Midtre Lovenbreen. The prodeltas registered a net growth from 2009 to 2012: the biggest, located in the prolongation of deltas of Austre Lovenbreen, measured 1033 m in length in 2009 and 1180 m in length in 2012. This substantial amount of sediment supplied in the fjord has an impact on the fjord ecology, especially on the benthic ecosystem.
Programme: 1172
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Cristofari Robin, Bertorelle Giorgio, Ancel André, Benazzo Andrea, Le Maho Yvon, Ponganis Paul J., Stenseth Nils Christian, Trathan Phil N., Whittington Jason D., Zanetti Enrico, Zitterbart Daniel P., Trucchi Emiliano & Le Bohec Céline. (2016). Full circumpolar migration ensures evolutionary unity in the Emperor penguin. Nature communications, 7, 11842.
Abstract: Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species’ response to global environmental change is likely to follow a shared evolutionary trajectory.
Programme: 137
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C. Genthon, D. Six, C. Scarchilli, V. Ciardini and M. Frezzotti. (2016). Meteorological and snow accumulation gradients across Dome C, East Antarctic plateau . International journal of climatology, 36(1).
Abstract: In situ observations show that snow accumulation is ∼10% larger 25 km north than south of the summit of Dome C on the east antarctic plateau. The mean wind direction is southerly. Although a slight slope-related diverging katabatic flow component is detectable, the area is an essentially flat (∼10 m elevation change or less) homogeneous snow surface. The European Center for Medium-range Weather Forecasts meteorological analyses data reproduce a significant accumulationgradient and suggest that 90% of the the mean accumulation results from the 25% largest precipitation events. During these events, air masses originate from coastal areas in the north rather than from inland in the south. Radiative cooling condensation occurs on the way across the dome and as the moisture reservoir is depleted less snow is dumped 25 km south than north, withlittle direct impact from the local (50-km scale) topography. Air masses are warmer on average, and warmer north than south, when originating from the coast. This marginally affects the mean temperature gradients. The moisture gradients are more affected because moisture is nonlinearly related to temperature: the mean atmospheric moisture is larger north than south.Significant meteorological and hydrological gradients over such relatively small distances (50 km) over locally flat region may be an issue when interpreting ice cores: although cores are drilled at the top of domes and ridges where the slopes andelevation gradients are minimal, they sample small surfaces in areas affected by significant eteorological and hydrologicalspatial gradients.
Programme: 411
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C. Larose, A. Morris, T. M. Vogel. (2016). Carbon and temperature effects on microbial communities living in the snow.
Abstract: This is a presentation given at the ISME meeting in Montreal, August 2016
Programme: 399
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Camille Moreau, Thomas Saucède, Quentin Jossart, Antonio Agüera, Arnaud Brayard & Bruno Danis. (2016). Reproductive strategy as a piece of the biogeographic puzzle: a case study using Antarctic sea stars (Echinodermata, Asteroidea). J. Biogeogr., 44(4), 848–860.
Abstract: Aim To describe and analyse asteroid biogeographic patterns in the Southern Ocean (SO) and test whether reproductive strategy (brooder versus broadcaster) can explain distribution patterns at the scale of the entire class. We hypothesize that brooding and broadcasting species display different biogeographic patterns. Location Southern Ocean, south of 45 °S. Methods Over 14,000 asteroid occurrences are analysed using bootstrapped spanning network (BSN), non-metrical multidimensional scaling (nMDS) and clustering to uncover the spatial structure of faunal similarities among 25 bioregions. Results Main biogeographic patterns are congruent with previous works based on other taxa and highlight the isolation of New Zealand, the high richness in the Scotia Arc area particularly of brooding species, an East/West Antarctic differentiation, and the faunal affinities between South America and sub-Antarctic Islands. Asteroids show lower endemism levels than previously reported with 29% of species occurring in Antarctica only. In particular, asteroids from Tierra del Fuego showed affinities with those of West Antarctica at the species level, suggesting a recent mixing of assemblages. Biogeographic patterns are highly linked to reproductive strategy. Patterns also differ according to the taxonomic level, revealing the underlying role of historical factors. Main conclusions Patterns of sea star biogeography are consistent with results obtained for other marine groups and are strongly linked to reproductive strategy.
Programme: 1044
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Della Penna, A., Koubbi, P., Cotte, C., Bon, C., Bost, C.A., d'Ovidio, F. . (2016). Lagrangian analysis of multi-satellite data in support of open ocean Marine Protected Area design. Deep Sea Res. Part II Top. Stud. Oceanogr., .
Abstract: Compared to ecosystem conservation in territorial seas, protecting the open ocean has peculiar geopolitical, economic and scientific challenges. One of the major obstacle is defining the boundary of an open ocean Marine Protected Area (MPA). In contrast to coastal ecosystems, which are mostly constrained by topographic structures fixed in time, the life of marine organisms in the open ocean is entrained by fluid dynamical structures like eddies and fronts, whose lifetime occurs on ecologically-relevant timescales. The position of these highly dynamical structures can vary interannually by hundreds of km, and so too will regions identified as ecologically relevant such as the foraging areas of marine predators. Thus, the expected foraging locations suggested from tracking data cannot be directly extrapolated beyond the year in which the data were collected. Here we explore the potential of Lagrangian methods applied to multisatellite data as a support tool for a MPA proposal by focusing on the Crozet archipelago oceanic area (Indian Sector of the Southern Ocean). By combining remote sensing with biologging information from a key marine top predator (Eudyptes chrysolophus, or Macaroni penguin) of the Southern Ocean foodweb, we identify a highly dynamic branch of the Subantarctic front as a foraging hotspot. By tracking this feature in historical satellite data (1993–2012) we are able to extrapolate the position of this foraging ground beyond the years in which tracking data are available and study its spatial variability.
Programme: 394
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Duputel, Z., J. Vergne, L. Rivera, G. Wittlinger, V. Farra, and G. Hetényi. (2016). The 2015 Gorkha earthquake: A large event illuminating the Main Himalayan Thrust fault. Geophysical research letters, 43(6), 2016GL068083.
Abstract: The 2015 Gorkha earthquake sequence provides an outstanding opportunity to better characterize the geometry of the Main Himalayan Thrust (MHT). To overcome limitations due to unaccounted lateral heterogeneities, we perform Centroid Moment Tensor inversions in a 3-D Earth model for the main shock and largest aftershocks. In parallel, we recompute S-to-P and P-to-S receiver functions from the Hi-CLIMB data set. Inverted centroid locations fall within a low-velocity zone at 10–15 km depth and corresponding to the subhorizontal portion of the MHT that ruptured during the Gorkha earthquake. North of the main shock hypocenter, receiver functions indicate a north dipping feature that likely corresponds to the midcrustal ramp connecting the flat portion to the deep part of the MHT. Our analysis of the main shock indicates that long-period energy emanated updip of high-frequency radiation sources previously inferred. This frequency-dependent rupture process might be explained by different factors such as fault geometry and the presence of fluids.
Programme: 133
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