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Jan Jansen, Piers K. Dunstan, Nicole A. Hill, Philippe Koubbi, Jessica Melbourne-Thomas, Romain Causse, Craig R. Johnson. (2020). Integrated assessment of the spatial distribution and structural dynamics of deep benthic marine communities (Vol. 30).
Abstract: Characterizing the spatial distribution and variation of species communities and validating these characteristics with data from the field are key elements for an ecosystem-based approach to management. However, models of species distributions that yield community structure are usually not linked to models of community dynamics, constraining understanding and management of the ecosystem, particularly in data-poor regions. Here we use a qualitative network model to predict changes in Antarctic benthic community structure between major marine habitats characterized largely by seafloor depth and slope, and use multivariate mixture models of species distributions to validate the community dynamics. We then assess how future increases in primary production associated with anticipated loss of sea-ice may affect the ecosystem. Our study shows how both spatial and structural features of ecosystems in data-poor regions can be analyzed and possible futures assessed, with direct relevance for ecosystem-based management.
Keywords: Antarctica continental shelf deep sea ecosystem dynamic ecosystem structure qualitative network model Southern Ocean spatial model species archetype model upper slope
Programme: 281
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. (2020). Antarctic krill (Euphausia superba) in a warming ocean: thermotolerance and deciphering Hsp70 responses (Vol. 25).
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. (2020). Low fitness at low latitudes: Wintering in the tropics increases migratory delays and mortality rates in an Arctic breeding shorebird (Vol. 89).
Keywords: demography fitness migration nutrient storage strategies site fidelity solar geolocation survival timing
Programme: 1036
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Jouanneau W, Léandri-Breton DJ, Moe B, Parenteau C, Herzke D, Elliott K, Gabrielsen GW, Chastel O. (2020). Transfert maternel de contaminants et perturbation endocrine chez un oiseau marin Arctique.
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. (2020). Genome-wide analyses reveal drivers of penguin diversification (Vol. 117). Bachelor's thesis, , .
Abstract: Penguins are the only extant family of flightless diving birds. They currently comprise at least 18 species, distributed from polar to tropical environments in the Southern Hemisphere. The history of their diversification and adaptation to these diverse environments remains controversial. We used 22 new genomes from 18 penguin species to reconstruct the order, timing, and location of their diversification, to track changes in their thermal niches through time, and to test for associated adaptation across the genome. Our results indicate that the penguin crown-group originated during the Miocene in New Zealand and Australia, not in Antarctica as previously thought, and that Aptenodytes is the sister group to all other extant penguin species. We show that lineage diversification in penguins was largely driven by changing climatic conditions and by the opening of the Drake Passage and associated intensification of the Antarctic Circumpolar Current (ACC). Penguin species have introgressed throughout much of their evolutionary history, following the direction of the ACC, which might have promoted dispersal and admixture. Changes in thermal niches were accompanied by adaptations in genes that govern thermoregulation and oxygen metabolism. Estimates of ancestral effective population sizes (Ne) confirm that penguins are sensitive to climate shifts, as represented by three different demographic trajectories in deeper time, the most common (in 11 of 18 penguin species) being an increased Ne between 40 and 70 kya, followed by a precipitous decline during the Last Glacial Maximum. The latter effect is most likely a consequence of the overall decline in marine productivity following the last glaciation.
Keywords: ancestral distribution ancestral niche Antarctica genome penguin
Programme: 137,354
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. (2020). Decadal changes in blood ?13C values, at-sea distribution, and weaning mass of southern elephant seals from Kerguelen Islands (Vol. 287). Bachelor's thesis, , .
Keywords: bio-logging decadal change foraging habitat Indian sector of the Southern Ocean population strategies stable isotopes
Programme: 109,1201
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. (2020). An update on Inuit perceptions of their changing environment, Qikiqtaaluk (Baffin Island, Nunavut) (Vol. 8).
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Julien Collet, Henri Weimerskirch. (2020). Albatrosses can memorize locations of predictable fishing boats but favour natural foraging (Vol. 287).
Keywords: albatrosses anthropogenic food cognition in the wild fisheries individual consistency resource predictability
Programme: 109
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. (2020). A Micro-Mechanical Model for the Transformation of Dry Polar Firn Into Ice Using the Level-Set Method (Vol. 8).
Abstract: Interpretation of greenhouse gas records in polar ice cores requires a good understanding of the mechanisms controlling gas trapping in polar ice, and therefore of the processes of densification and pore closure in firn (compacted snow). Current firn densification models are based on a macroscopic description of the firn and rely on empirical laws and/or idealized geometries to obtain the equations governing the densification and pore closure. Here, we propose a physically-based methodology explicitly representing the porous structure and its evolution over time. In order to handle the complex geometry and topological changes that occur during firn densification, we rely on a Level-Set representation of the interface between the ice and the pores. Two mechanisms are considered for the displacement of the interface: (i) mass surface diffusion driven by local pore curvature and (ii) ice dislocation creep. For the latter, ice is modeled as a viscous material and the flow velocities are solutions of the Stokes equations. First applications show that the model is able to densify firn and split pores. Using the model in cold and arid conditions of the Antarctic plateau, we show that gas trapping models do not have to consider the reduced compressibility of closed pores compared to open pores in the deepest part of firns. Our results also suggest that the mechanism of curvature-driven surface diffusion does not result in pore splitting, and that ice creep has to be taken into account for pores to close. Future applications of this type of model could help quantify the evolution and closure of firn porous networks for various accumulation and temperature conditions.
Programme: 1153
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Korbinian Sager, Christian Boehm, Laura Ermert, Lion Krischer, Andreas Fichtner. (2020). Global-Scale Full-Waveform Ambient Noise Inversion (Vol. 125).
Abstract: We present the first application of full-waveform ambient noise inversion to observed correlation functions that jointly constrains 3-D Earth structure and heterogeneous noise sources. For this, we model and interpret ambient noise correlations as recordings of correlation wavefields, which completely eliminates the limiting assumptions of Green's function retrieval, such as equipartitioning and homogeneous random noise sources. Our method accounts for seismic wave propagation physics in 3-D heterogeneous and attenuating media and also for the heterogeneous and nonstationary nature of the ambient noise field. Designed as a proof of concept, the study considers long periods from 100 to 300 s, thus focusing on the Earth's hum. Treating correlations as self-consistent observables allows us to make separate measurements on the causal and acausal branches of correlation functions, without any need to choose one of them or form the average. We validate our approach by assessing the quality of the obtained models and by comparing them to previous studies. This work is a step toward the establishment of full-waveform ambient noise inversion as a tomographic technique with the goal to go beyond ambient noise tomography based on Green's function retrieval.
Keywords: computational seismology full-waveform inversion global tomography interferometry seismic noise
Programme: 133
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