Boulinier, T., Betoulle, S., Caza, F., St Pierre, Y., Tornos, J., Gamble, A. &Amp; Tasiemski, A. (2020). Panorama des recherches et des derniers résultats sur les pathogènes en milieu polaire. Bachelor's thesis, , .
Abstract: Approches complémentaires des interactions hôte-parasite en zones polaire: de la détection de parasites et agents infectieux à l'étude fonctionnelle, écologique et évolutive de leurs interactions avec leurs hôtes.
Programme: 333,1151
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Brigitte Van Vliet-Lanoë, Oskar Knudsen, Agust Guðmundsson, Hervé Guillou, Gilles Chazot, Jessica Langlade, Céline Liorzou, Philippe Nonnotte. (2020). Volcanoes and climate: the triggering of preboreal Jökulhlaups in Iceland (Vol. 109).
Abstract: The Early Holocene (12–8.2 cal ka) deglaciation and pulsed warming was associated in Iceland with two major generations of jökulhlaups around the Vatna ice-cap (Vatnajökull), at ca 11.4–11.2 cal ka and ca 10.4–9.9 cal ka, and major tephra emissions from the Grímsvötn and Bárðarbunga subglacial volcanoes. The earliest flood events were recorded inland during the Middle Younger Dryas and their deposits were overlain by the Early Preboreal Vedde Ash (11.8 cal ka). The first Holocene flood events (ca 11.4–11.2 cal ka) are issued from a glacial advance. The second, and major, set of floods was partly driven by the Erdalen cold events and advances (10.1–9.7 10Be ka) initially issued from the Bárðarbunga (10.4, 10.1–9.9 ka) and Grímsvötn volcanoes (Saksunarvatn tephra complex, ca. 10.2–9.9 cal ka). These floods were also fed by the residual glacio-isostatic depressions below the Vatnajökull that enabled the storage of meltwaters in large subglacial lakes or aquifers until ca. 9.3 cal ka. This storage was enhanced by ice-damming and permafrost, especially during the twinned Erdalen events. Due to the glacio-isostatic rebound, the general slope was nearly flat, and the valley was partly filled with sediments until ca 10.8 cal ka. Temporary lacustrine deposits in this valley resulted from the very broad splay of waters as for the ca 11.2 cal ka and ca 10.1–9.9 cal ka flood, due to regional permafrost. These floods had a potential duration of several months as they were mostly fed by climate-driven meltwater. The maximal volume evacuated by these events did not greatly exceed 1 × 106 m3 s−1 from the flood-affected transverse profile of the valleys that remain partly filled with sediments.
Programme: 316
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C Engrand, E Charon, H Le- Roux, M Marinova, J Duprat, E Dartois, B Guérin, J Rojas, L Delauche, M Godard, D Troadec. (2020). Evidence of irradiation in interplanetary space in minerals from an ultracarbonaceous Antarctic micrometeorites (UCAMM).
Abstract: Introduction: Ultracarbonaceous Antarctic Micrometeorites (UCAMMs) are dominated by N-rich polyaromatic organic matter exhibiting large D enrichments [1-5]. The high abundance of organic matter exhibiting large D enrichment suggests a cometary origin for UCAMMs [1-3]. Three kinds of organic matter are identified in UCAMMs, with different nitrogen abundances and highly variable concentrations of small (typically 30-500 nanometer) mineral aggregates embedded in the organic matter [5-8]. We focus here on a mineral assemblage embedded in one UCAMM that exhibits evidence of ion irradiation, to get insight on the formation and evolution of this cometary particle. Sample and methods: A fragment of UCAMM DC06-06-43 (hereafter DC06-43) was carbon coated, observed by SEM/EDX, and a 100 nm thick FIB section of this fragment was made at IEMN Lille. The size of the initial UCAMM before fragmentation was ~ 25 x 30 µm. After STXM-XANES analysis, the mineralogy of the sample was investigated by TEM at UMET Lille using a FEI Tecnai G2 20 at 200 kV and FEI TITAN Themis at 300 kV [9]. Results : TEM examination reveals a large assemblage of crystalline minerals at the center of the DC06-43 UCAMM fragment, surrounded by organic matter (Figure 1) [9]. The assemblage consists of µm-to subµm sized Mg-rich pyroxenes, a large “triskell”-shaped Fe-sulfide, a few Mg-rich olivines, and minor Si-Al-Carich amorphous pockets and Fe-Ni metal. About 28 crystalline pyroxenes are identified whereas only 5 olivine crystals are observed in the section. GEMS are present embedded in the organic matter, close to the crystalline assemblage. We identified irradiation features (rims and tracks) in pyroxene grains. No rims or tracks were found in olivine. We observed irradiated rims around six pyroxenes at the top of the section (Figure 1, light blue labels). One pyroxene shows a continuous irradiated rim (Figure 2 top). Rim thicknesses range from 20 to 100 nm, with an average of 60 ± 20 nm (1σ) (Figure 2 bottom). Fe-rich deposits are occasionally found on top of irradiated rims. EDX mappings and profiles show that the rims are strongly depleted in Mg (Figure 3). The average track density in pyroxene grains measured over an area of 4.5 x 10-8 cm 2 is 1.3 x 10 10 cm-2 with one value at 3.8 x 10 9 cm-2 , the other values ranging from 9.5 x 10 9 to 3.2 x 10 10 cm-2 (Figure 4). Irradiation track lengths
Programme: 1120
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C. A. González-Wevar, N. I. Segovia, S. Rosenfeld, D. Noll, C. S. Maturana, M. Hüne, J. Naretto, K. Gérard, A. Díaz, H. G. Spencer, T. Saucède, J. -P. Féral, S. A. Morley, P. Brickle, N. G. Wilson, E. Poulin. (2020). Contrasting biogeographical patterns in Margarella (Gastropoda: Calliostomatidae: Margarellinae) across the Antarctic Polar Front (Vol. 156).
Abstract: Members of the trochoidean genus Margarella (Calliostomatidae) are broadly distributed across Antarctic and sub-Antarctic ecosystems. Here we used novel mitochondrial and nuclear gene sequences to clarify species boundaries and phylogenetic relationships among seven nominal species distributed on either side of the Antarctic Polar Front (APF). Molecular reconstructions and species-delimitation analyses recognized only four species: M. antarctica (the Antarctic Peninsula), M. achilles (endemic to South Georgia), M. steineni (South Georgia and Crozet Island) and the morphologically variable M. violacea (=M. expansa, M. porcellana and M. pruinosa), with populations in southern South America, the Falkland/Malvinas, Crozet and Kerguelen Islands. Margarella violacea and M. achilles are sister species, closely related to M. steineni, with M. antarctica sister to all these. This taxonomy reflects contrasting biogeographic patterns on either side of the APF in the Southern Ocean. Populations of Margarella north of the APF (M. violacea) showed significant genetic variation but with many shared haplotypes between geographically distant populations. By contrast, populations south of the APF (M. antarctica, M. steineni and M. achilles) exhibited fewer haplotypes and comprised three distinct species, each occurring across a separate geographical range. We hypothesize that the biogeographical differences may be the consequence of the presence north of the APF of buoyant kelps – potential long-distance dispersal vectors for these vetigastropods with benthic-protected development – and their near-absence to the south. Finally, we suggest that the low levels of genetic diversity within higher-latitude Margarella reflect the impact of Quaternary glacial cycles that exterminated local populations during their maxima.
Keywords: Antarctic Polar Front Benthic-protected development Long-distance dispersal Rafting Southern Ocean
Programme: 1044
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C. Michelot, A. Kato, T. Raclot, K. Shiomi, P. Goulet, P. Bustamante, Y. Ropert-Coudert. (2020). Sea-ice edge is more important than closer open water access for foraging Adélie penguins: evidence from two colonies (Vol. 640).
Abstract: Sentinel species, like Adélie penguins, have been used to assess the impact of environmental changes, and their link with sea ice has received considerable attention. Here, we tested if foraging Adélie penguins from 2 colonies in East Antarctica target the distant sea-ice edge or take advantage of closer open waters that are readily available near their colony. We examined the foraging behaviour of penguins during the incubation trips of females in 2016 and males in 2017, using GPS tracking and diet data in view of daily sea-ice data and bathymetry. In 2016-2017, sea-ice cover was extensive during females’ trips but flaw leads and polynyas were close to both study sites. Sea ice receded rapidly during males’ trips in 2017-2018. Despite close open water near both colonies in both years, females and males preferentially targeted the continental slope and the sea-ice edge to forage. In addition, there was no difference in the diet of penguins from both colonies: all penguins fed mostly on Antarctic krill and males also foraged on Antarctic silverfish. Our results highlight the importance of the sea-ice edge for penguins, an area where food abundance is predictable. It is likely that resource availability was not sufficient in closer open water areas at such an early stage in the breeding season. The behaviours displayed by the penguins from both colonies were similar, suggesting a common behaviour across colonies in Terre Adélie, although additional sites would be necessary to confirm this hypothesis.
Keywords: Colony Diet GPS Incubation trip Pygoscelis adeliae Sea-ice edge Stable isotopes
Programme: 1091
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Calas A. (2020). Image analysis of settlement plates for monitoring marine benthic communities of the Kerguelen Islands.
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Casado M., Leroy-Dos C., Fourre E., Favier V., Agosta C., Arnaud L., Prié F., Akers P., Janssen L., Savarino J., Landais A. (2020). Water vapor isotopic signature along the EAIIST traverse.
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Catalina Morales-Yáñez, Zacharie Duputel, Luis Rivera. (2020). Impact of 3-D Earth structure on W-phase CMT parameters (Vol. 223).
Abstract: We investigate the impact of unmodelled 3-D structural heterogeneity on inverted W-phase source parameters. We generate a large data set of synthetic seismograms accounting for the Earths 3-D structure for 250 earthquakes globally distributed. The W-phase algorithm is then used to invert for earthquake CMT parameters, assuming a spherical Earth model. The impact of lateral heterogeneity is assessed by comparing inverted source parameters with those used to compute the 3-D synthetics. Results show that the 3-D structure mainly affects centroid location while the effect on the other source parameters remains small. Centroid mislocations present clear geographical patterns. In particular, W-phase solutions for earthquakes in South America are on average biased 17 km to the east of the actual centroid locations. This effect is significantly reduced using an azimuthally well balanced distribution of seismological stations. Source parameters are generally more impacted by mantle heterogeneity while the scalar moment of shallow earthquakes seems to be mainly impacted by the crustal structure. Shallow earthquakes present a variability of Mrθ and Mrϕ moment tensor elements, resulting both from the small amplitude and a larger uncertainty of the associated Green’s functions.
Programme: 133
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Charles Amory. (2020). Drifting-snow statistics from multiple-year autonomous measurements in Adélie Land, East Antarctica (Vol. 14).
Abstract: Drifting snow is a widespread feature over the Antarctic ice sheet, whose climatological and hydrological significance at the continental scale have been consequently investigated through modelling and satellite approaches. While field measurements are needed to evaluate and interpret model and satellite products, most drifting-snow observation campaigns in Antarctica involved data collected at a single location and over short time periods. With the aim of acquiring new data relevant to the observation and modelling of drifting snow in Antarctic conditions, two remote locations in coastal Adélie Land (East Antarctica) that are 100 km apart were instrumented in January 2010 with meteorological and second-generation IAV Engineering acoustic FlowCapt™ sensors. The data, provided nearly continuously so far, constitute the longest dataset of autonomous near-surface (i.e. within 2 m) measurements of drifting snow currently available over the Antarctic continent. This paper presents an assessment of drifting-snow occurrences and snow mass transport from up to 9 years (2010–2018) of half-hourly observational records collected in one of the Antarctic regions most prone to snow transport by wind. The dataset is freely available to the scientific community and can be used to complement satellite products and evaluate snow-transport models close to the surface and at high temporal frequency.
Programme: 1013
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Charlotte Groult. (2020). Effet des marées sur la cryo-sismicité côtière en Antarctique. Bachelor's thesis, , .
Abstract: L’étude sismologique de la glace permet de mieux comprendre la déformation des systèmes glaciaires et leur stabilité́ dans un contexte de réchauffement climatique global. La cryosphère est très active sismiquement. De nombreux évènements comme des icequakes, des trémors glaciaires ou des évènements à l’interface glace/terre solide émanent de la base des glaciers, des marges de cisaillement, des vêlages au front des glaciers ou encore des chenaux d’eau sous- glaciaire. Nous avons observé les signaux d’une dizaine de stations sismologiques sur les côtes de l’antarctique et parmi tous les évènements visibles, un signal de quelques heures présente une forte répétabilité́ dans le temps et dans l’espace. Pour l’étudier nous avons extrait des séries temporelles d’énergie sismique sur trois stations : drv, thur, vna1 et nous avons montré sa modulation avec les forçages de marée d’abord sur l’année 2018 puis sur 8 ans à thur, 10 ans à vna1 et 20 ans à drv. Le signal d’énergie sismique présente toutes les périodicités des forçages de marée avec cependant quelques décalages temporels, indicateurs de délais de réponse du système glaciaire et d’un comportement rhéologique viscoélastique de la glace.
Programme: 133
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