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Author |
Kévin Fourteau, Fabien Gillet-Chaulet, Patricia Martinerie, Xavier Faïn |
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Title |
A Micro-Mechanical Model for the Transformation of Dry Polar Firn Into Ice Using the Level-Set Method |
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2020 |
Publication |
Frontiers in Earth Science |
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8 |
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Pages |
101 |
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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. |
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1153 |
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2296-6463 |
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yes |
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8268 |
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Author |
Alexandra Lavrillier |
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Title |
“Spirit-Charged” Humans in Siberia: Interrelations between the Notions of the Individual (“Spirit Charge” and “Active Imprint”) and (Ritual) Action |
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Year |
2020 |
Publication |
Arctic Anthropology |
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Volume |
57 |
Issue |
1 |
Pages |
72-99 |
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This paper shows how a society imagines human individuals and their power to act upon spirits both ritually and materially. Based on the author’s fieldwork (from 1994 to 2019), it analyzes the emic concept onnir, which is omnipresent in the daily activities and the past and present collective/individual rituals of Siberian Evenki and Even. Each human owns a specific fluctuating “charge made of spirits” and an “active imprint” that empowers the human to act, perform rituals, develop talents, and create. Even after death, this “imprint” affects everything and everyone a human ever touched. Onnir defines the interrelations between the individual, the spirits of his or her own “charge,” and the spirits of the universe in an “active agent”-“patient” relationship. This paper contributes to studies of the notions of the individual, “playing” as a ritual means, the acceptance/rejection of neoshamans, neorituals, and the (ritual) agency of ordinary individuals. |
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1127 |
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0066-6939, 1933-8139 |
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8079 |
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C. Michelot, A. Kato, T. Raclot, K. Shiomi, P. Goulet, P. Bustamante, Y. Ropert-Coudert |
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Title |
Sea-ice edge is more important than closer open water access for foraging Adélie penguins: evidence from two colonies |
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Year |
2020 |
Publication |
Marine Ecology Progress Series |
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Volume |
640 |
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215-230 |
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Keywords |
Colony Diet GPS Incubation trip Pygoscelis adeliae Sea-ice edge Stable isotopes |
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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. |
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1091 |
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0171-8630, 1616-1599 |
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0171-8630, 1616-1599 |
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yes |
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7680 |
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Author |
Hochstrasser-Petit Ch., Romanova L., Duchesne S., Melnichuk O., Gérard P. |
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Title |
Yakut clothes of the 17th and 18th centuries, archaeology and restitution. |
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Journal |
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Year |
2020 |
Publication |
Vest. archeol. anthropol. i etnogr |
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4 |
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Pages |
131-147 |
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40 Frozen Yakutian Graves, From The 17th To The 19th Century Allow The Reconstitution Of Clothes. At The End Of the 17th Century, New Fashions Are Emerging With The Ostentatious Use Of Imported Goods And The Influences Of russian Noble Circles And Chinese And/or Mongol And/or Buriat Fashions. The Garment Does Not Only Seem To Be any More An Element Of Protection Against The Cold And A Utilitarian Object But Becomes A Way To Marking The Socialization of The Individual. |
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1038 |
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yes |
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8058 |
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Sylvie Duchesne, R Bravina, V POPOV, S Kolodeznikov, P Gérard, V Myglan, Ch Hochstrasser-Petit, L Romanova, M Petit, N Kirianov, A Alexeev, L Alekseeva, A Riberon, E Crubézy |
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Title |
Frozen graves of Yakutia, a chronological sequence |
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Year |
2020 |
Publication |
VESTNIK ARHEOLOGII, ANTROPOLOGII I ETNOGRAFII |
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Volume |
4 |
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Pages |
120-130 |
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Keywords |
artefacts Christianization chronology funeral practices modern period soil burial Yakutia Yakuts |
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Distribution, cultural and chronological attribution of frozen graves of Yakutia between the beginning of 17th and end of 19th century. The funerary rites and the artefacts allow to differentiate four chrono-cultural periods (before 1700 AD, from 1700 to 1750 AD, from 1750 to 1800 AD and after 1800 AD) which could be associated with historical events: opening of the trading post of Nertchinsk, expansion of the Kangalasky clan, economic collapse, generalization of Christianization. |
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1038 |
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yes |
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Serial |
8012 |
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Author |
Helle A. Pedersen, Nicolas Leroy, Dimitri Zigone, Martin Vallée, Adam T. Ringler, David C. Wilson |
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Title |
Using Component Ratios to Detect Metadata and Instrument Problems of Seismic Stations: Examples from 18 Yr of GEOSCOPE Data |
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Year |
2020 |
Publication |
Seismological research letters |
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Volume |
91 |
Issue |
1 |
Pages |
272-286 |
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Abstract |
Replacement or deterioration of seismic instruments and the evolution of the installation conditions and sites can alter the seismic signal in very subtle ways; therefore, it is notoriously difficult to monitor the signal quality of permanent seismic stations. We present a simple way to characterize and monitor signal quality, using energy ratios between each pair of the three components, as a complement to existing methods. To calculate stable daily energy ratios over a large frequency range (0.01–5 Hz), we use the daily median energy ratio over all 5 min windows within the day. The method is applied to all GEOSCOPE stations, for continuous BH channel data collected since 2001. We show applications to identify past gain problems (stations ROCAM and CRZF), to provide feedback after field interventions at remote sites (Antarctic station DRV), and to shed light on complex instrument problems (stations ECH and KIP). Our results show that component energy ratios have excellent time resolution and that they are visually simple for identification of problems. They can be used both for ongoing continuous monitoring of the signal quality, or as a tool to identify past problems. The Python code to produce the results in this work and the Python code for daily monitoring used by GEOSCOPE are available (see Data and Resources). |
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133 |
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yes |
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7672 |
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Author |
Isabelle Badenhausser, Lise Chambrin, Marc Lebouvier |
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Title |
Guide d'identification des plantes des îles sub-Antarctiques Crozet et Kerguelen |
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Book |
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Year |
2020 |
Publication |
1e édition, imprimerie nouvelle biard |
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Pages |
151 p |
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136 |
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978-2-7380-1440-5 |
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7975 |
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Mathieu Ardyna, C. J. Mundy, Matthew M. Mills, Laurent Oziel, Pierre-Luc Grondin, Léo Lacour, Gauthier Verin, Gert van Dijken, Joséphine Ras, Eva Alou-Font, Marcel Babin, Michel Gosselin, Jean-Éric Tremblay, Patrick Raimbault, Philipp Assmy, Marcel Nicolaus, Hervé Claustre, Kevin R. Arrigo |
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Title |
Environmental drivers of under-ice phytoplankton bloom dynamics in the Arctic Ocean |
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Year |
2020 |
Publication |
Elementa: Science of the Anthropocene |
Abbreviated Journal |
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Volume |
8 |
Issue |
30 |
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Abstract |
The decline of sea-ice thickness, area, and volume due to the transition from multi-year to first-year sea ice has improved the under-ice light environment for pelagic Arctic ecosystems. One unexpected and direct consequence of this transition, the proliferation of under-ice phytoplankton blooms (UIBs), challenges the paradigm that waters beneath the ice pack harbor little planktonic life. Little is known about the diversity and spatial distribution of UIBs in the Arctic Ocean, or the environmental drivers behind their timing, magnitude, and taxonomic composition. Here, we compiled a unique and comprehensive dataset from seven major research projects in the Arctic Ocean (11 expeditions, covering the spring sea-ice-covered period to summer ice-free conditions) to identify the environmental drivers responsible for initiating and shaping the magnitude and assemblage structure of UIBs. The temporal dynamics behind UIB formation are related to the ways that snow and sea-ice conditions impact the under-ice light field. In particular, the onset of snowmelt significantly increased under-ice light availability (>0.1–0.2 mol photons m–2 d–1), marking the concomitant termination of the sea-ice algal bloom and initiation of UIBs. At the pan-Arctic scale, bloom magnitude (expressed as maximum chlorophyll a concentration) was predicted best by winter water Si(OH)4 and PO43– concentrations, as well as Si(OH)4:NO3– and PO43–:NO3– drawdown ratios, but not NO3– concentration. Two main phytoplankton assemblages dominated UIBs (diatoms or Phaeocystis), driven primarily by the winter nitrate:silicate (NO3–:Si(OH)4) ratio and the under-ice light climate. Phaeocystis co-dominated in low Si(OH)4 (i.e., NO3:Si(OH)4 molar ratios >1) waters, while diatoms contributed the bulk of UIB biomass when Si(OH)4 was high (i.e., NO3:Si(OH)4 molar ratios <1). The implications of such differences in UIB composition could have important ramifications for Arctic biogeochemical cycles, and ultimately impact carbon flow to higher trophic levels and the deep ocean. |
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1164 |
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2325-1026 |
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yes |
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8115 |
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Blanche Saint-Béat, Brian D. Fath, Cyril Aubry, Jonathan Colombet, Julie Dinasquet, Louis Fortier, Virginie Galindo, Pierre-Luc Grondin, Fabien Joux, Catherine Lalande, Mathieu LeBlanc, Patrick Raimbault, Télesphore Sime-Ngando, Jean-Eric Tremblay, Daniel Vaulot, Frédéric Maps, Marcel Babin |
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Title |
Contrasting pelagic ecosystem functioning in eastern and western Baffin Bay revealed by trophic network modeling |
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Year |
2020 |
Publication |
Elementa: science of the anthropocene |
Abbreviated Journal |
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Volume |
8 |
Issue |
1 |
Pages |
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Baffin Bay, located at the Arctic Ocean’s ‘doorstep’, is a heterogeneous environment where a warm and salty eastern current flows northwards in the opposite direction of a cold and relatively fresh Arctic current flowing along the west coast of the bay. This circulation affects the physical and biogeochemical environment on both sides of the bay. The phytoplanktonic species composition is driven by its environment and, in turn, shapes carbon transfer through the planktonic food web. This study aims at determining the effects of such contrasting environments on ecosystem structure and functioning and the consequences for the carbon cycle. Ecological indices calculated from food web flow values provide ecosystem properties that are not accessible by direct in situ measurement. From new biological data gathered during the Green Edge project, we built a planktonic food web model for each side of Baffin Bay, considering several biological processes involved in the carbon cycle, notably in the gravitational, lipid, and microbial carbon pumps. Missing flow values were estimated by linear inverse modeling. Calculated ecological network analysis indices revealed significant differences in the functioning of each ecosystem. The eastern Baffin Bay food web presents a more specialized food web that constrains carbon through specific and efficient pathways, leading to segregation of the microbial loop from the classical grazing chain. In contrast, the western food web showed redundant and shorter pathways that caused a higher carbon export, especially via lipid and microbial pumps, and thus promoted carbon sequestration. Moreover, indirect effects resulting from bottom-up and top-down control impacted pairwise relations between species differently and led to the dominance of mutualism in the eastern food web. These differences in pairwise relations affect the dynamics and evolution of each food web and thus might lead to contrasting responses to ongoing climate change. |
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1164 |
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2325-1026 |
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yes |
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8113 |
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Gustavo Yunda-Guarin, Thomas A. Brown, Loïc N. Michel, Blanche Saint-Béat, Rémi Amiraux, Christian Nozais, Philippe Archambault |
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Reliance of deep-sea benthic macrofauna on ice-derived organic matter highlighted by multiple trophic markers during spring in Baffin Bay, Canadian Arctic |
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2020 |
Publication |
Elementa: Science of the Anthropocene |
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8 |
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1 |
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Benthic organisms depend primarily on seasonal pulses of organic matter from primary producers. In the Arctic, declines in sea ice due to warming climate could lead to changes in this food supply with as yet unknown effects on benthic trophic dynamics. Benthic consumer diets and food web structure were studied in a seasonally ice-covered region of Baffin Bay during spring 2016 at stations ranging in depth from 199 to 2,111 m. We used a novel combination of highly branched isoprenoid (HBI) lipid biomarkers and stable isotope ratios (δ13C, δ15N) to better understand the relationship between the availability of carbon sources in spring on the seafloor and their assimilation and transfer within the benthic food web. Organic carbon from sea ice (sympagic carbon [SC]) was an important food source for benthic consumers. The lipid biomarker analyses revealed a high relative contribution of SC in sediments (mean SC% ± standard deviation [SD] = 86% ± 16.0, n = 17) and in benthic consumer tissues (mean SC% ± SD = 78% ± 19.7, n = 159). We also detected an effect of sea-ice concentration on the relative contribution of SC in sediment and in benthic consumers. Cluster analysis separated the study region into three different zones according to the relative proportions of SC assimilated by benthic macrofauna. We observed variation of the benthic food web between zones, with increases in the width of the ecological niche in zones with less sea-ice concentration, indicating greater diversity of carbon sources assimilated by consumers. In zones with greater sea-ice concentration, the higher availability of SC increased the ecological role that primary consumers play in driving a stronger transfer of nutrients to higher trophic levels. Based on our results, SC is an important energy source for Arctic deep-sea benthos in Baffin Bay, such that changes in spring sea-ice phenology could alter benthic food-web structure. |
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1164 |
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2325-1026 |
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yes |
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8119 |
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