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Author |
Y. Quesnel, W. Zylberman, P. Rochette, M. Uehara, J. Gattacceca, G. R. Osinski, P. Dussouillez, C. Lepaulard, C. Champollion |
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Title |
Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada |
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Journal |
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Year |
2020 |
Publication |
Meteoritics & Planetary Science |
Abbreviated Journal |
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Volume |
55 |
Issue |
3 |
Pages |
480-495 |
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Abstract |
In 2011, the discovery of shatter cones confirmed the 28 km diameter Tunnunik complex impact structure, Northwest Territories, Canada. This study presents the first results of ground-based electromagnetic, gravimetric, and magnetic surveys over this impact structure. Its central area is characterized by a 10 km wide negative gravity anomaly of about 3 mGal amplitude, roughly corresponding to the area of shatter cones, and associated with a positive magnetic field anomaly of 120 nT amplitude and 3 km wavelength. The latter correlates well with the location of the deepest uplifted strata, an impact-tilted Proterozoic dolomite layer of the Shaler Supergroup exposed near the center of the structure and intruded by dolerite dykes. Locally, electromagnetic field data unveil a conductive superficial formation which corresponds to an 80–100 m thick sand layer covering the impact structure. Based on the measurements of magnetic properties of rock samples, we model the source of the magnetic anomaly as the magnetic sediments of the Shaler Supergroup combined with a core of uplifted crystalline basement with enhanced magnetization. More classically, the low gravity signature is attributed to a reduction in density measured on the brecciated target rocks and to the isolated sand formations. However, the present-day fractured zone does not extend deeper than 1 km in our model, indicating a possible 1.5 km of erosion since the time of impact, about 430 Ma ago. |
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1139 |
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ISSN |
1945-5100 |
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yes |
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8266 |
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Author |
Alice Gadea, Mathieu Fanuel, Anne-Cécile Le Lamer, Joël Boustie, Hélène Rogniaux, Maryvonne Charrier, Françoise Lohézic-Le Devehat |
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Title |
Mass Spectrometry Imaging of Specialized Metabolites for Predicting Lichen Fitness and Snail Foraging |
Type |
Journal |
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Year |
2020 |
Publication |
Plants |
Abbreviated Journal |
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Volume |
9 |
Issue |
1 |
Pages |
70 |
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Keywords |
Notodiscus hookeri Pseudocyphellaria crocata Chemical Ecology Lichens Lobariaceae Mass Spectrometry Imaging Optimal Defense Theory Specialized Metabolites |
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Abstract |
Lichens are slow-growing organisms supposed to synthetize specialized metabolites to protect themselves against diverse grazers. As predicted by the optimal defense theory (ODT), lichens are expected to invest specialized metabolites in higher levels in reproductive tissues compared to thallus. We investigated whether Laser Desorption Ionization coupled to Mass Spectrometry Imaging (LDI-MSI) could be a relevant tool for chemical ecology issues such as ODT. In the present study, this method was applied to cross-sections of thalli and reproductive tissues of the lichen Pseudocyphellaria crocata. Spatial mapping revealed phenolic families of metabolites. A quantification of these metabolites was carried out in addition to spatial imaging. By this method, accumulation of specialized metabolites was observed in both reproductive parts (apothecia and soralia) of P. crocata, but their nature depended on the lichen organs: apothecia concentrated norstictic acid, tenuiorin, and pulvinic acid derivatives, whereas soralia mainly contained tenuiorin and pulvinic acid. Stictic acid, tenuiorin and calycin, tested in no-choices feeding experiments, were deterrent for N. hookeri while entire thalli were consumed by the snail. To improve better knowledge in relationships between grazed and grazing organisms, LDI-MSI appears to be a complementary tool in ecological studies |
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136 |
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yes |
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Serial |
8265 |
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Author |
Lia Siegelman, Patrice Klein, Pascal Rivière, Andrew F. Thompson, Hector S. Torres, Mar Flexas, Dimitris Menemenlis |
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Title |
Enhanced upward heat transport at deep submesoscale ocean fronts |
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Journal |
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Year |
2020 |
Publication |
Nature Geoscience |
Abbreviated Journal |
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Volume |
13 |
Issue |
1 |
Pages |
50-55 |
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Keywords |
Physical oceanography |
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Abstract |
The ocean is the largest solar energy collector on Earth. The amount of heat it can store is modulated by its complex circulation, which spans a broad range of spatial scales, from metres to thousands of kilometres. In the classical paradigm, fine oceanic scales, less than 20 km in size, are thought to drive a significant downward heat transport from the surface to the ocean interior, which increases oceanic heat uptake. Here we use a combination of satellite and in situ observations in the Antarctic Circumpolar Current to diagnose oceanic vertical heat transport. The results explicitly demonstrate how deep-reaching submesoscale fronts, with a size smaller than 20 km, are generated by mesoscale eddies of size 50–300 km. In contrast to the classical paradigm, these submesoscale fronts are shown to drive an anomalous upward heat transport from the ocean interior back to the surface that is larger than other contributions to vertical heat transport and of comparable magnitude to air–sea fluxes. This effect can remarkably alter the oceanic heat uptake and will be strongest in eddy-rich regions, such as the Antarctic Circumpolar Current, the Kuroshio Extension and the Gulf Stream, all of which are key players in the climate system. |
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Programme |
109,1201 |
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Thesis |
Bachelor's thesis |
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ISSN |
1752-0908 |
ISBN |
1752-0908 |
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yes |
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Call Number |
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Serial |
8264 |
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Author |
Jan Jansen, Piers K. Dunstan, Nicole A. Hill, Philippe Koubbi, Jessica Melbourne-Thomas, Romain Causse, Craig R. Johnson |
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Title |
Integrated assessment of the spatial distribution and structural dynamics of deep benthic marine communities |
Type |
Journal |
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Year |
2020 |
Publication |
Ecological Applications |
Abbreviated Journal |
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Volume |
30 |
Issue |
3 |
Pages |
e02065 |
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Keywords |
Antarctica continental shelf deep sea ecosystem dynamic ecosystem structure qualitative network model Southern Ocean spatial model species archetype model upper slope |
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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. |
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281 |
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ISSN |
1939-5582 |
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yes |
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Call Number |
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Serial |
8263 |
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Author |
Renac Christophe, Moine Bertrand, Goudour Jean-Pierre, LeRomancer Marc, Perrache Chantal |
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Title |
Stable isotope study of rainfall, river drainage and hot springs of the kerguelen archipelago, SW Indian Ocean |
Type |
Journal |
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Year |
2020 |
Publication |
Geothermics |
Abbreviated Journal |
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Volume |
83 |
Issue |
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Pages |
101726 |
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Keywords |
Geothermal springs Kerguelen archipelago Stable isotope composition Water-Rock interaction |
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Abstract |
This study is the first synthesis of chemical composition and stable isotopes values for the Kerguelen archipelago waters. The stable isotope values for rainfall and river waters in the Kerguelen archipelago allow a calculation of the Local Meteoric Water Line (δD rainfall = 8.43 x δ18O rainfall + 11) and a summer runoff line (δD river drainage = 7.45 x δ18O river drainage + 6). Surface waters with low- ion concentrations, chlorine facies and stable isotope values infiltrate through fractures and lava flows recharging deeper groundwaters. Thermal groundwater with low- (7 to 50 °C) and high- (50 to 100 °C) temperatures emerges in different localities in the volcanic archipelago. The low-temperature thermal waters might represent a mixture of high-temperature water with rainfall, thermal gradient changes or shallower infiltration compared to that for high-temperature thermal waters. The Rallier du Baty and Val Travers areas contain geothermal fluids with high-temperature springs, fumaroles and a large water flow. In the Rallier du Baty, the major ion chemistry and O, H, C and S stable isotope ratio of low (7 to 50 °C) temperature spring waters in Rallier du Baty area demonstrate a geothermal-system recharged by meteoric water (δD H2O liquid = 7.0 x δ18O H2O liquid + 0.5) rather than sea water. The chemical and isotopic compositions of elevated temperature spring waters (50 to 100 °C) have a long and complex history of meteoric water interacting with cooling magmas (δD H2O liquid = 1.78 x δ18O H2O liquid – 23). Surficial precipitation of aragonite, kaolinite, pyrite, native sulfur attest to a long livied geothermal system. A temperature of the geothermal reservoir has been estimated between 193 and 259 °C by cation geothermometry. The combination of minerals observed, major ion composition of water with thermodynamic modeling and stable isotope data suggest a geothermal system with a series of water/rock interactions from 50 to 250 °C. The conductive cooling of rising of H2O−CO2-rich fluids have produced a H2O−CO2 phase separation with the precipitation of secondary minerals. |
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Programme |
408,444 |
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Thesis |
Bachelor's thesis |
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ISSN |
0375-6505 |
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yes |
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Call Number |
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Serial |
8262 |
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Author |
Samuel Veilleux, Najat Bhiry, Armelle Decaulne |
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Title |
Talus slope characterization in Tasiapik Valley (subarctic Québec): Evidence of past and present slope processes |
Type |
Journal |
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Year |
2020 |
Publication |
Geomorphology |
Abbreviated Journal |
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Volume |
349 |
Issue |
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Pages |
106911 |
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Keywords |
Morphometry Nunavik Periglacial Slope dynamics Snow avalanches |
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Abstract |
Topographic, granulometric, morphometric, petrographic and vegetation surveys were conducted on the slopes of Tasiapik Valley, near Umiujaq (Nunavik), to document mass wasting processes and their geomorphological impact. Talus slopes, widespread at the foot of the steep rockwalls of Tasiapik Valley, are an important landscape feature in the area. The lithology of the slope deposits attest their local origin, namely the result of rockfalls coming from the adjacent wall. Locally, poor vegetation covering the clasts exhibits recently fallen debris; elsewhere, dense shrub cover has colonized the slopes demonstrating the low activity nowadays. On-going periglacial processes have led to extensive dismantling of the rockface, enabling for debris supply. Following the last deglaciation, paraglacial processes have potentially favoured slope instabilities. The use of automatic cameras during the winter 2017–2018 resulted in the observation of many snow-avalanche events; however few rockfall events have been observed. Spring snow avalanches have carried rock debris to the talus at the foot of the slope; snow also enabled debris redistribution on the slopes. |
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Programme |
1148 |
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Edition |
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ISSN |
0169-555X |
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Approved |
yes |
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Call Number |
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Serial |
8261 |
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Author |
Patrick Pomerleau, Alain Royer, Alexandre Langlois, Patrick Cliche, Bruno Courtemanche, Jean-Benoît Madore, Ghislain Picard, Éric Lefebvre |
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Title |
Low Cost and Compact FMCW 24 GHz Radar Applications for Snowpack and Ice Thickness Measurements |
Type |
Journal |
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Year |
2020 |
Publication |
Sensors |
Abbreviated Journal |
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Volume |
20 |
Issue |
14 |
Pages |
3909 |
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Keywords |
Antarctica Arctic snow tundra Frequency-Modulated Continuous-Wave (FMCW) radar lake ice thickness snow boreal forest snow density snow monitoring snow water equivalent snow wetness subarctic snow taiga |
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Abstract |
Monitoring the evolution of snow on the ground and lake ice—two of the most important components of the changing northern environment—is essential. In this paper, we describe a lightweight, compact and autonomous 24 GHz frequency-modulated continuous-wave (FMCW) radar system for freshwater ice thickness and snow mass (snow water equivalent, SWE) measurements. Although FMCW radars have a long-established history, the novelty of this research lies in that we take advantage the availability of a new generation of low cost and low power requirement units that facilitates the monitoring of snow and ice at remote locations. Test performance (accuracy and limitations) is presented for five different applications, all using an automatic operating mode with improved signal processing: (1) In situ lake ice thickness measurements giving 2 cm accuracy up to ≈1 m ice thickness and a radar resolution of 4 cm; (2) remotely piloted aircraft-based lake ice thickness from low-altitude flight at 5 m; (3) in situ dry SWE measurements based on known snow depth, giving 13% accuracy (RMSE 20%) over boreal forest, subarctic taiga and Arctic tundra, with a measurement capability of up to 3 m in snowpack thickness; (4) continuous monitoring of surface snow density under particular Antarctic conditions; (5) continuous SWE monitoring through the winter with a synchronized and collocated snow depth sensor (ultrasonic or LiDAR sensor), giving 13.5% bias and 25 mm root mean square difference (RMSD) (10%) for dry snow. The need for detection processing for wet snow, which strongly absorbs radar signals, is discussed. An appendix provides 24 GHz simulated effective refractive index and penetration depth as a function of a wide range of density, temperature and wetness for ice and snow. |
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Programme |
1110 |
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yes |
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Call Number |
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Serial |
8232 |
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Author |
Héloïse Barbel, Dominique Todisco, Najat Bhiry |
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Title |
A geochemical investigation of an Early Inuit semi-subterranean winter dwelling in a periglacial context |
Type |
Journal |
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Year |
2020 |
Publication |
Journal of archaeological science: reports |
Abbreviated Journal |
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Volume |
33 |
Issue |
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Pages |
102552 |
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Keywords |
C-N analysis Cryosolic soils geochemistry FTIR ICP-AES Inuit archaeology Nunavik Semi-subterranean house |
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Abstract |
Geochemical investigations using FTIR, ICP-AES and C-N analyses were carried out on a single-family semi-subterranean Inuit house in order to assess the contribution of Inuit domestic activities in the formation of cryosolic soils in a periglacial archaeological context (Kuuvik Bay, Nunavik, Canada). The geochemical elements data were analyzed using box plots and enrichment factors. The information was also summarized and visualized through principal component analysis (PCA). These complementary statistical approaches provided evidence of a moderate but identifiable and significant imprint of Inuit domestic activities on soil geochemistry. The box plots indicate moderate Ca, Mn, Cu and P enrichments and more noticeable Mg, Fe and S enrichments. These enrichment factors and the ICP-AES data show that samples from the peripheral wall and the tunnel entrance of the house and its vicinity are significantly enriched. While FTIR analysis highlighted the main soil element contents (e.g., organic and mineral components), ICP-AES analysis was used to further document variations in the background elements throughout the site. However, the obtained results do not allow us to undertake a spatial analysis of Inuit activities or to describe them in detail. In addition, the data highlight the difficulty of documenting the natural variability of element contents in cryosolic soils, especially in archaeological contexts. Cryo-pedological processes in the active layer as well as house cleaning and nutrient inputs resulting from Inuit occupations may have attenuated chemical signatures of previous Inuit domestic activities. |
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Programme |
1080 |
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Campaign |
LOTECHAIN |
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Address |
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Corporate Author |
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Thesis |
Bachelor's thesis |
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Edition |
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ISSN |
2352-409X |
ISBN |
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Notes |
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Approved |
yes |
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Call Number |
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Serial |
8206 |
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| Permanent link to this record |
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Author |
Chuxian Li, Jeroen E. Sonke, Gaël Le Roux, Nathalie Van der Putten, Natalia Piotrowska, Catherine Jeandel, Nadine Mattielli, Mathieu Benoit, Giles F. S. Wiggs, François De Vleeschouwer |
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Title |
Holocene dynamics of the southern westerly winds over the Indian Ocean inferred from a peat dust deposition record |
Type |
Journal |
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Year |
2020 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
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Volume |
231 |
Issue |
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Pages |
106169 |
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Keywords |
Amsterdam Island Anthropogenic activities Dust sources Peat Southern westerly winds |
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Abstract |
The southern westerly winds (SWW) play a major role in climate variability in Southern Hemisphere mid- and high-latitudes, regulating rainfall, ocean circulation, and the Southern Ocean carbon sink. Despite their importance, little is known about millennial scale changes in the SWW and how they have influenced the climate system in the past and interacted with the Earth’s surface elements, such as dust, nutrients and carbon. Here we present a dust record from a 6.6 kyr old peat core in Amsterdam Island (AMS) situated at the northern edge of the SWW (37°S) in the Southern Indian Ocean. Mineral dust flux was used to track atmospheric dust production, long-distance transport and subsequent deposition. Dust provenance was determined from rare earth element (REE) and Nd isotopic signatures (εNd) in the peat core, compared with a reference dataset of Southern Hemisphere dust sources. Using a multi-proxy mixing model, the εNd and REE ratios show a relatively uniform mixture of ca. 40% local, 15% Southern African and 45% Southern South American dust sources since 6.6 cal kyr BP. However, from 1910 AD onwards, there is a doubling in the contribution from Southern Africa (32%). Two mineral dust flux minima occur at 6.2–4.9 cal kyr BP and 3.9–2.7 cal kyr BP, interpreted as periods with equatorward-shifted and/or strengthened SWW at the northern edge of the wind belt. Conversely, periods of higher dust flux at 6.6–6.2 cal kyr BP, 4.9–3.9 cal kyr BP, and 1.4 cal kyr BP onwards are interpreted as poleward-shifted and/or weakened SWW. These interpretations are based on the findings that higher (lower) wind speeds lead to enhanced (less) removal of distal dust on the way to AMS, by wet deposition and turbulence. Published Holocene SWW records at the northern edge of the wind belt (33–41°S) covering South-America, Southern-Africa and Australia, show much variability over the last 6.6 kyr. We suggest this reflects complex regional climate variability in the different SH longitudinal sectors, indicating that SWW are not zonally homogeneous at the northern edge of the wind belt. The recent shift in dust provenance is not accompanied by enhanced total dust deposition at AMS. We therefore suggest that human impact (e.g., land use changes) and drier climate conditions in Southern Africa have led to enhanced dust mobilization. |
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Programme |
1065,1133 |
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Thesis |
Bachelor's thesis |
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Edition |
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ISSN |
0277-3791 |
ISBN |
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yes |
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Call Number |
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Serial |
8193 |
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| Permanent link to this record |
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Author |
Guillaumot Charlène, Danis Bruno, Saucède Thomas |
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Title |
Selecting environmental descriptors is critical for modelling the distribution of Antarctic benthic species |
Type |
Journal |
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Year |
2020 |
Publication |
Polar Biology |
Abbreviated Journal |
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Volume |
43 |
Issue |
9 |
Pages |
1363-1381 |
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Keywords |
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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. |
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1044,1124 |
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Bachelor's thesis |
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1432-2056 |
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yes |
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8184 |
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