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Eymar-Dauphin Pauline. (2020). Réponses des plantes aquatiques des Iles Kerguelen à l’intensification des contraintes thermiques de leur habitat. Approche par les hypervolumes. Master 2 ECOMONT, Université de Savoie Mont-Blanc (encadrement : A.-K. Bittebiere).
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F. Pitout, A. Marchaudon, K. J. Trattner, J. Berchem, H. Laakso, C. P. Escoubet. (2020). Simultaneous Polar and Cluster Observations in the Northern and Southern Middle-Altitude Polar Cusps Around Equinox (Vol. 125).
Abstract: We present an event of simultaneous observations of the northern and southern middle-altitude polar cusps by the Polar spacecraft and Cluster fleet that occurred on 23 September 2004. We examine the possible asymmetries in the fields and plasma parameters, although the proximity of the equinox should limit these asymmetries. Ion sensors reveal two dispersions in both cusps, and data analysis leads to the conclusion that those dispersions are due to pulsed reconnection at a single X-line, which runs along the subsolar magnetopause. While the electromagnetic and particle energy fluxes injected in both cusp are globally very similar, we report significant differences in ion dispersions, width of the low-latitude boundary layer, and peak convection velocities. We ascribe these differences to the dipole tilt that introduces an asymmetry in the magnetosheath flow at the exterior cusps.
Keywords: dayside magnetosphere hemispheric asymmetry polar cusp
Programme: 312
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Fabienne Joliet, Véronique Van Tilbeurgh, Anne Atlan. (2020). La valeur d’existence du monde vivant selon les Inuits du Nunavik et les Occidentaux aux Kerguelen (Vol. 732).
Abstract: Dans le contexte actuel de transition socio-écologique internationale, l’objectif de cet article est d’interroger la relation entre les humains et les autres vivants et choses naturelles dans les derniers espaces de vaste naturalité aux pôles. C’est à travers la notion de valeur d’existence que cette relation sera analysée dans ses retranchements chez les Inuits qui habitent le Nunavik en subarctique et les Occidentaux qui veillent sur les Kerguelen en subantarctique. Plus particulièrement, c’est la nature du lien qu’ils entretiennent avec les vivants non-humains et autres choses naturelles, et ses registres de valeurs qui sont étudiées.Ces enquêtes boréales et australes en zone protégée ou bien à ses abords montrent ainsi que ce qui prédomine, c’est le fait qu’il est attribué aux éléments naturels une valeur d’existence en fonction d’un esprit commun spirituel ou bien d’une enveloppe commune charnelle d’« être vivant ». Selon ces principes, les modalités prises par l’attribution de la valeur d’existence changent : les humains se concevant soit, comme une partie d’un ensemble au même titre que les autres vivants et choses naturelles ayant un esprit ou conscience, soit comme maîtres et protecteurs des autres vivants et choses naturelles, en tant qu’ayant une fonction dominante au sein d’« êtres vivants ». Dans cette perspective, le territoire joue un rôle spécifique favorisant l’existence même de cette valeur au-delà de ses fonctions de régulation couramment retenues.
Programme: 136
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Fabrizio Magrini, Dario Jozinović, Fabio Cammarano, Alberto Michelini, Lapo Boschi. (2020). Local earthquakes detection: A benchmark dataset of 3-component seismograms built on a global scale (Vol. 1).
Abstract: Machine learning is becoming increasingly important in scientific and technological progress, due to its ability to create models that describe complex data and generalize well. The wealth of publicly-available seismic data nowadays requires automated, fast, and reliable tools to carry out a multitude of tasks, such as the detection of small, local earthquakes in areas characterized by sparsity of receivers. A similar application of machine learning, however, should be built on a large amount of labeled seismograms, which is neither immediate to obtain nor to compile. In this study we present a large dataset of seismograms recorded along the vertical, north, and east components of 1487 broad-band or very broad-band receivers distributed worldwide; this includes 629,095 3-component seismograms generated by 304,878 local earthquakes and labeled as EQ, and 615,847 ones labeled as noise (AN). Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings, even if applied in regions not represented in the training set. Achieving an accuracy of 96.7, 95.3, and 93.2% on training, validation, and test set, respectively, we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm, and makes it applicable to real-time detection of local events. We make the database publicly available, intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.
Keywords: Benchmark dataset Earthquake detection algorithm Seismology Supervised machine learning
Programme: 133
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Fort, J., Grémillet, D., Helgason, H.H., Albert, C., Amélineau, F., Anker-Nilssen, T., Angelier, F., Bråthen, V.S., Bringsvor, I.S., Carlsen, T.H., Chastel, O., Cherenkov, A., Christensen-Dalsgaard, S., Danielsen, J., Daunt, F., Descamps, S., Dietz, R., Elliott, K., Erikstad, K.E., Eulaers, I., Ezhov, A., Fauchald, P., Fifield, D., Frederiksen, M., Gabrielsen, G.W., Gavrilo, M., Gilchrist, G., Gilg, O., Giraudeau, M., Gíslason, S., Golubova, E., Hallgrimsson, G.T., Hansen, E.S., S.A., H., Hatch, S., Helberg, M., Huffeldt, N.P., Jónsson, J.E., Kitaysky, A., Kolbeinsson, Y., Krasnov, Y., Langset, M., Latty, C., Leclaire, S., Lorentsen, S.H., Lorentzen, E., Love, O., Mallory, M., Merkel, B., Merkel, F., Moe, B., Montevecchi, W.A., Mosbech, A., Newell, M., Olsen, B., Orben, R., Parkinson, K., Patterson, A., Pratte, I., Provencher, J., Ragnarsdottir, S.B., Reiertsen, T.K., Renner, H., Robertson, G.J., Rojek, N., M, R., Sagerup, K., Semashko, V., Sepp, T., Sonne, C., Systad, G.H., Takahashi, A., Tarroux, A., Tertitski, G., Thompson, P., Tolmacheva, E., Will, A., Wojczulanis-Jakubas, K., Tórarinsson, T.L., Bustamante, P. & Strøm, H. (2020). Mercury contamination of Arctic seabirds : spatio-temporal trends and impacts.
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Franz Slemr, Lynwill Martin, Casper Labuschagne, Thumeka Mkololo, Hélène Angot, Olivier Magand, Aurélien Dommergue, Philippe Garat, Michel Ramonet, Johannes Bieser. (2020). Atmospheric mercury in the Southern Hemisphere – Part 1: Trend and inter-annual variations in atmospheric mercury at Cape Point, South Africa, in 2007–2017, and on Amsterdam Island in 2012–2017 (Vol. 20). Bachelor's thesis, , .
Abstract: The Minamata Convention On Mercury (Hg) Entered Into Force In 2017, Committing Its 116 Parties (As Of January 2019) To Curb Anthropogenic Emissions. Monitoring Of Atmospheric Concentrations And Trends Is An Important Part Of The Effectiveness Evaluation Of The Convention. A Few Years Ago (In 2017) We Reported An Increasing Trend In Atmospheric Hg Concentrations At The Cape Point Global Atmosphere Watch (Gaw) Station In South Africa (34.3535∘ S, 18.4897∘ E) For The 2007–2015 Period. With 2 More Years Of Measurements At Cape Point And The 2012–2017 Data From Amsterdam Island (37.7983∘ S, 77.5378∘ E) In The Remote Southern Indian Ocean, A More Complex Picture Emerges: At Cape Point The Upward Trend For The 2007–2017 Period Is Still Significant, But No Trend Or A Slightly Downward Trend Was Detected For The Period 2012–2017 At Both Cape Point And Amsterdam Island. The Upward Trend At Cape Point Is Driven Mainly By The Hg Concentration Minimum In 2009 And Maxima In 2014 And 2012. Using Ancillary Data On 222rn, Co, O3, Co2, And Ch4 From Cape Point And Amsterdam Island, The Possible Reasons For The Trend And Its Change Are Investigated. In A Companion Paper This Analysis Is Extended For The Cape Point Station By Calculations Of Source And Sink Regions Using Backward-trajectory Analysis.
Programme: 416,1028
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Frédéric Angelier, Olivier Chastel, Adam Z. Lendvai, Charline Parenteau, Henri Weimerskirch, John C. Wingfield. (2020). When do older birds better resist stress? A study of the corticosterone stress response in snow petrels (Vol. 16). Bachelor's thesis, Royal Society, .
Abstract: Life-history theory predicts that, to optimize their fitness, individuals should increase their reproductive effort as their residual reproductive value decreases. Accordingly, several studies have shown that individuals downregulate their glucocorticoid stress response (a proxy of reproductive investment in vertebrates) as they age, and as the subsequent reproductive value decreases. However, and surprisingly, results appear inconsistent, suggesting that the environmental context or the individual state may affect the relationship between age and reproductive effort. Here, we tested for the first time this hypothesis, and more specifically, whether this attenuation of the corticosterone stress response with advancing age depends on the energetic status of individuals. We compared the influence of age on the corticosterone stress response between fasting and non-fasting breeding snow petrels (Pagodroma nivea), an extremely long-lived bird. As expected, we found that the corticosterone stress response was attenuated in old petrels, but only when they were not fasting. Interestingly, this pattern was not apparent in fasting petrels, suggesting that old birds downregulate their corticosterone stress response and increase their parental investment only when they are in good body condition. At the ultimate level, old individuals may maintain a strong corticosterone stress response when fasting because the survival costs of increased stress resistance and parental effort might then outweigh their reproductive benefits.
Programme: 109
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G. Hubert, S. Aubry. (2020). Study of the Impact of Past Extreme Solar Events on the Modern Air Traffic (Vol. 19).
Abstract: The ancient solar energetic particle (SEP) events of 774/775 CE and 993/994 CE were characterized thanks to radionuclide productions stored in environmental archives as ice cores or tree rings. Primary cosmic ray spectra deduced from these cosmogenic isotope data indicate that the impact of these extreme SEP events would have been much more significant than any of the ones observed during the modern era. However, the impact of these should be studied more accurately in the framework of the ambient dose equivalent impacting aircrew and passengers in the air traffic context by considering physical parameters such as time profile or anisotropy properties. In this study, the impact that 774/775 CE and 993/994 CE past extreme SEP events could have had on modern air traffic is discussed. Possible event spectra for these ancient events are derived from the spectra ground-level enhancement (GLE) 5 and GLE 69, which have been observed during the modern era and have been widely studied/characterized using measurements. The investigations include the impact of the SEP activity on ambient dose equivalent, including detailed analyses considering route, airplane characteristics (departure, arrival, continent, airplane type), and the time occurrence of the SEP event. Statistical analyses show that additional dose levels can reach values on the order of 70 mSv, which is absolutely significant considering the current air traffic recommendations. The orders of magnitude of the ambient dose equivalent induced during past extreme SEP events raises a number of issues, both for aircrews and for avionics hardware. This study demonstrates that simulations can be useful for the evaluation of risks in case of extreme SEP events.
Programme: 1112
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Guillaumot Charlène, Danis Bruno, Saucède Thomas. (2020). Selecting environmental descriptors is critical for modelling the distribution of Antarctic benthic species (Vol. 43). Bachelor's thesis, , .
Abstract: Species distribution models (SDMs) are increasingly used in ecological and biogeographic studies by Antarctic biologists, including for conservation and management purposes. During the modelling process, model calibration is a critical step to ensure model reliability and robustness, especially in the case of SDMs, for which the number of selected environmental descriptors and their collinearity is a recurring issue. Boosted regression trees (BRT) was previously considered as one of the best modelling approach to correct for this type of bias. In the present study, we test the performance of BRT in modelling the distribution of Southern Ocean species using different numbers of environmental descriptors, either collinear or not. Models are generated for six sea star species with contrasting ecological niches and wide distribution ranges over the entire Southern Ocean. For the six studied species, overall modelling performance is not affected by the number of environmental descriptors used to generate models, BRT using the most informative descriptors and minimizing model overfitting. However, removing collinear descriptors also helps reduce model overfitting. Our results confirm that BRTs may perform well and are relevant to deal with complex and redundant environmental information for Antarctic biodiversity distribution studies. Selecting a limited number of non-collinear descriptors before modelling may generate simpler models and facilitate their interpretation. The modelled distributions do not differ noticeably between the different species despite contrasting species ecological niches. This unexpected result stresses important limitations in using SDMs for broad scale spatial studies, based on limited, spatially aggregated data, and low-resolution descriptors.
Programme: 1044,1124
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Guillot T. (2020). Discovering Exoplanets from Antarctica with ASTEP. Bachelor's thesis, , .
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