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Author |
Winton V.H.L., Ming A., Caillon N., Hauge L. Jones A.E., Savarino J., Yang X., Frey M.M. |
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Year |
2020 |
Publication |
Atmospheric Chemistry and Physics |
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Volume |
20 |
Issue  |
9 |
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Programme |
1177 |
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Bachelor's thesis |
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ISSN |
1680-7316 |
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yes |
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Serial |
7855 |
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Author |
Weisen Shen, Douglas A. Wiens, Sridhar Anandakrishnan, Richard C. Aster, Peter Gerstoft, Peter D. Bromirski, Samantha E. Hansen, Ian W. D. Dalziel, David S. Heeszel, Audrey D. Huerta, Andrew A. Nyblade, Ralph Stephen, Terry J. Wilson, J. Paul Winberry |
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Title |
The Crust and Upper Mantle Structure of Central and West Antarctica From Bayesian Inversion of Rayleigh Wave and Receiver Functions |
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Year |
2018 |
Publication |
Journal of Geophysical Research: Solid Earth |
Abbreviated Journal |
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Volume |
123 |
Issue |
9 |
Pages |
7824-7849 |
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Keywords |
ambient noise tomography Antarctica crust and uppermost mantle Gamburtsev Mountains seismology Transantarctic Mountains |
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Abstract |
We construct a new seismic model for central and West Antarctica by jointly inverting Rayleigh wave phase and group velocities along with P wave receiver functions. Ambient noise tomography exploiting data from more than 200 seismic stations deployed over the past 18 years is used to construct Rayleigh wave phase and group velocity dispersion maps. Comparison between the ambient noise phase velocity maps with those constructed using teleseismic earthquakes confirms the accuracy of both results. These maps, together with P receiver function waveforms, are used to construct a new 3-D shear velocity (Vs) model for the crust and uppermost mantle using a Bayesian Monte Carlo algorithm. The new 3-D seismic model shows the dichotomy of the tectonically active West Antarctica (WANT) and the stable and ancient East Antarctica (EANT). In WANT, the model exhibits a slow uppermost mantle along the Transantarctic Mountains (TAMs) front, interpreted as the thermal effect from Cenozoic rifting. Beneath the southern TAMs, the slow uppermost mantle extends horizontally beneath the traditionally recognized EANT, hypothesized to be associated with lithospheric delamination. Thin crust and lithosphere observed along the Amundsen Sea coast and extending into the interior suggest involvement of these areas in Cenozoic rifting. EANT, with its relatively thick and cold crust and lithosphere marked by high Vs, displays a slower Vs anomaly beneath the Gamburtsev Subglacial Mountains in the uppermost mantle, which we hypothesize may be the signature of a compositionally anomalous body, perhaps remnant from a continental collision. |
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133 |
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ISSN |
2169-9356 |
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yes |
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Call Number |
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Serial |
7878 |
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Title |
Mineralogy and oxygen isotope systematics of magnetite grains and a magnetite-dolomite assemblage in hydrated fine-grained Antarctic micrometeorites |
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Journal |
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Year |
2019 |
Publication |
Meteoritics & Planetary Science |
Abbreviated Journal |
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Volume |
54 |
Issue |
9 |
Pages |
1973-1989 |
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1120 |
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ISSN |
1945-5100 |
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yes |
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Serial |
7898 |
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Title |
Snow microbiome functional analyses reveal novel aspects of microbial metabolism of complex organic compounds |
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Journal |
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Year |
2020 |
Publication |
MicrobiologyOpen |
Abbreviated Journal |
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Volume |
9 |
Issue |
9 |
Pages |
e1100 |
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Keywords |
metagenome metatranscriptome mi-faser snow microbiome |
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Abstract |
Microbes active in extreme cold are not as well explored as those of other extreme environments. Studies have revealed a substantial microbial diversity and identified cold-specific microbiome molecular functions. We analyzed the metagenomes and metatranscriptomes of 20 snow samples collected in early and late spring in Svalbard, Norway using mi-faser, our read-based computational microbiome function annotation tool. Our results reveal a more diverse microbiome functional capacity and activity in the early- vs. late-spring samples. We also find that functional dissimilarity between the same-sample metagenomes and metatranscriptomes is significantly higher in early than late spring samples. These findings suggest that early spring samples may contain a larger fraction of DNA of dormant (or dead) organisms, while late spring samples reflect a new, metabolically active community. We further show that the abundance of sequencing reads mapping to the fatty acid synthesis-related microbial pathways in late spring metagenomes and metatranscriptomes is significantly correlated with the organic acid levels measured in these samples. Similarly, the organic acid levels correlate with the pathway read abundances of geraniol degradation and inversely correlate with those of styrene degradation, suggesting a possible nutrient change. Our study thus highlights the activity of microbial degradation pathways of complex organic compounds previously unreported at low temperatures. |
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1192 |
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ISSN |
2045-8827 |
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yes |
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Call Number |
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Serial |
7964 |
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Author |
O. I. Berngardt, J.-P. St- Maurice, J. M. Ruohoniemi, A. Marchaudon |
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Journal |
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Year |
2022 |
Publication |
Radio Science |
Abbreviated Journal |
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Volume |
57 |
Issue |
9 |
Pages |
e2021RS007338 |
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Keywords |
HF radars ionospheric absorption noise quiet-day curve radiowave propagation |
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Abstract |
Based on ray tracing in a smooth ionosphere described by the IRI-2012 model we have inferred the seasonal-diurnal dynamics of radio noise observed by four mid-latitude high-frequency (HF) radars. In the calculations, noise is assumed to be homogeneous and stationary, but the main contribution comes from the radar skip zone boundary due to focusing radiowaves effect. Noise absorption along the ray path is simulated from the IRI-2012 electron density, and from the molecular nitrogen density and electron temperatures obtained from the NRLMSISE-00 model. Earth magnetic field is not taken into account both in the absorption and ray-tracing calculations due to insufficient accuracy of the ionospheric model. The model results are compared with experimental radar data, and good agreement between the two is demonstrated. It is shown that experimentally observed seasonal and diurnal dynamics of the noise correlates well with model predictions. We demonstrated saturation effect at low noise levels. The model makes it possible to estimate the amount of absorption in D- and E-layers using noise observations at SuperDARN and SuperDARN-like poleward-oriented radars, especially at mid-latitudes. This is important for the retrieval of long term variations in the electron density in the lower ionosphere, by using wide coverage provided by these radars' network. The model also makes it feasible to interpret vertical absorption by experimental noise observations, thereby significantly expanding the capability of HF radars to monitor the lower ionosphere, and to provide data for joint analysis with other data, obtained by these radars at E- and F-layer heights. |
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312 |
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ISSN |
1944-799X |
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yes |
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Call Number |
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Serial |
8075 |
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Title |
What is the menu today in a subantarctic kelp food web from the Kerguelen Islands? Phytodetritus, phytoplankton and phytobenthos; not living kelp |
Type |
Journal |
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Year |
2022 |
Publication |
Marine Biology |
Abbreviated Journal |
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Volume |
169 |
Issue |
9 |
Pages |
118 |
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Keywords |
Benthic communities Food web Kelp forests Mixing models Stable isotopes |
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Abstract |
Kelp forests dominated by Macrocystis pyrifera are widely distributed in coastal waters from boreal, temperate and subantarctic regions. This widespread distribution may result in regional differences in food web structure and functioning. In temperate northern regions, where most studies on kelp forest benthic food webs have been conducted, kelp grazing is a well-documented phenomenon and can lead to the overgrazing of M. pyrifera by sea urchins when their predators (e.g., sea otters) are absent. In contrast, little is known about their counterparts in subantarctic areas. The present study aimed to reconstruct the benthic food web of a kelp forest dominated by M. pyrifera in a subantarctic environment using stable isotope analysis. Stable carbon (?13C), nitrogen (?15N) and sulfur (?34S) isotope ratios were measured from food sources (macrophytobenthos, suspended particulate organic matter SPOM, and sediment) and consumers (sponges, bivalves, gastropods, sedentary and mobile polychaetes, arthropods and echinoderms) which were sampled in a kelp forest of the Kerguelen archipelago. Mixing models highlighted two interconnected trophic pathways which were either supported by SPOM and resuspended macrophytobenthos detritus (bentho-pelagic), or by live micro/macrophytobenthos (phytobenthos-based). No major prey were highlighted for several consumers, indicating the existence of potential supplementary trophic pathways. No consumer relying primarily on living M. pyrifera was highlighted by the mixing models. The investigated kelp forest is hence a complex ecosystem supporting multiple trophic pathways, and direct consumption of M. pyrifera is limited. Nonetheless, M. pyrifera and other macrophytobenthos species may constitute a pool of detritus supporting several trophic pathways. |
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Programme |
1044 |
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ISSN |
1432-1793 |
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yes |
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Call Number |
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Serial |
8474 |
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Title |
Selecting environmental descriptors is critical for modelling the distribution of Antarctic benthic species |
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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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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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Programme |
1044,1124 |
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Bachelor's thesis |
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ISSN |
1432-2056 |
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yes |
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Call Number |
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Serial |
8184 |
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Title |
Regional modeling of surface mass balance on the Cook Ice Cap, Kerguelen Islands (49?S, 69?E) |
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Journal |
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Year |
2019 |
Publication |
Climate Dynamics |
Abbreviated Journal |
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Volume |
53 |
Issue |
9 |
Pages |
5909-5925 |
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Abstract |
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Programme |
1048 |
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ISSN |
1432-0894 |
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yes |
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Serial |
8185 |
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Title |
Theoretical and Experimental Analysis for Cleaning Ice Cores from EstisolTM 140 Drill Liquid |
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Year |
2021 |
Publication |
Applied Sciences |
Abbreviated Journal |
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Volume |
11 |
Issue |
9 |
Pages |
3830 |
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Keywords |
Beyond EPICA drilling Estisol ice cores |
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Programme |
1202 |
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yes |
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8247 |
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Title |
Global maps of soil temperature |
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Journal |
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Year |
2022 |
Publication |
Global Change Biology |
Abbreviated Journal |
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Volume |
28 |
Issue |
9 |
Pages |
3110-3144 |
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Keywords |
bioclimatic variables global maps microclimate near-surface temperatures soil temperature soil-dwelling organisms temperature offset weather stations |
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Abstract |
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Programme |
136 |
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ISSN |
1365-2486 |
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yes |
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Call Number |
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Serial |
8368 |
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