|
L A Ermert, K Sager, T Nissen-Meyer, A Fichtner. (2021). Multifrequency inversion of global ambient seismic sources (Vol. 225).
|
|
|
Jun Xie, Risheng Chu, Sidao Ni. (2021). Evaluating Global Tomography Models With Antipodal Ambient Noise Cross-Correlation Functions (Vol. 126).
Keywords: ambient noise cross-correlation functions antipodal surface waves mantle heterogeneity tomography model evaluation
Programme: 133
|
|
|
A. Baranov, R. Tenzer, A. Morelli. (2021). Updated Antarctic crustal model (Vol. 89).
Keywords: Antarctica Crustal structure Gondwana Sediments
Programme: 133
|
|
|
R. Olmi, M. Bittelli, G. Picard, L. Arnaud, A. Mialon, S. Priori. (2021). Investigating the influence of the grain size and distribution on the macroscopic dielectric properties of Antarctic firn (Vol. 185).
Keywords: Antarctica Close?off Dielectric measurements Dielectric model Firn Full wave EM simulations Ice cores
Programme: 1110
|
|
|
. (2021). Radar altimeter waveform simulations in Antarctica with the Snow Microwave Radiative Transfer Model (SMRT) (Vol. 263).
Abstract: Radar altimeters are important tools to monitor the volume of the ice sheets. The penetration of radar waves in the snowpack is a major source of uncertainty to retrieve surface elevation. To correct this effect, a better understanding of the sensitivity of the radar waveforms to snow properties is needed. Here, we present an extension of the Snow Model Radiative Transfer (SMRT) to compute radar waveforms and conduct a series of simulations on the Antarctic ice sheet. SMRT is driven by snow and surface roughness properties measured over a large latitudinal range during two field campaigns on the Antarctic Plateau. These measurements show that the snowpack is rougher, denser, less stratified, warmer, and has smaller snow grains near the coast than on the central Plateau. These simulations are compared to satellite observations in the Ka, Ku, and S bands. SMRT reproduces the observed waveforms well. For all sites and all sensors, the main contribution comes from the surface echo. The echo from snow grains (volume scattering) represents up to 40% of the amplitude of the total waveform power in the Ka band, and less at the lower frequencies. The highest amplitude is observed on the central Plateau due to the combination of higher reflection from the surface, higher scattering by snow grains in the Ka and Ku bands, and higher inter-layer reflections in the S band. In the Ka band, the wave penetrates in the snowpack less deeply on the central Plateau than near the coast because of the strong scattering caused by the larger snow grains. The opposite is observed in the S band, the wave penetrates deeper on the central Plateau because of the lower absorption due to the lower snow temperatures. The elevation bias caused by wave penetration into the snowpack show a constant bias of 10 cm for all sites in the Ka band, and a bias of 11 cm, and 21 cm in the Ku band for sites close to the coast and the central Plateau, respectively. Now that SMRT is performing waveform simulations, further work will address how the snowpack properties affect the parameters retrieved by more advanced retracking algorithms such as ICE-2 for different snow cover surfaces.
Keywords: Antarctic ice sheet Field measurements Modeling Radar altimetry Remote sensing SMRT Waveform
Programme: 1110
|
|
|
Pierre-Yves Pascal, Yann Reynaud, Elie Poulin, Chantal De Ridder, Thomas Saucede. (2021). Feeding in spatangoids: the case of Abatus Cordatus in the Kerguelen Islands (Southern Ocean) (Vol. 44).
Abstract: Irregular urchins exclusively live in marine soft bottom habitats, dwelling either upon or inside sediments and selectively picking up sediment grains and organic particles, or swallowing bulk sediment to feed on the associated organic matter. The exact food source and dietary requirements of most irregular echinoids, however, remain incompletely understood. The schizasterid species Abatus cordatus (Verrill, 1876) is a sub-Antarctic spatangoid that is endemic to the Kerguelen. The feeding behaviour of A. cordatus was investigated using simultaneously metabarcoding and stable isotope approaches. Comparison of ingested and surrounding sediments by metabarcoding revealed a limited selective ingestion of prokaryotes and eukaryotes by the urchin. Compared to surrounding sediments, the gut content had (i) higher carbon and nitrogen concentrations potentially due to selective ingestion of organic matter and/or the sea urchin mucus secretion and (ii) ?15N enrichment due to the selective assimilation of lighter isotope in the gut. Feeding experiments were performed using 13C and 15 N-enriched sediments in aquariums. The progression of stable isotope enrichment in proximal and distal parts of the digestive track of A. cordatus revealed that all particles are not similarly transported likely due to siphon functioning. Ingestion of water with associated dissolved and particulate organic matter should play an important role in urchin nutrition. A. cordatus had a gut resident time fluctuating between 76 and 101 h and an ingestion rate of 36 mg dry sediment h?1 suggesting that dense populations of the species may play a key ecological role through bioturbation in soft bottom shallow-water habitats of the Kerguelen Islands.
Programme: 1044
|
|
|
. (2021). Individual-based model of population dynamics in a sea urchin of the Kerguelen Plateau (Southern Ocean), Abatus cordatus, under changing environmental conditions (Vol. 440).
Keywords: Climate change Dynamic energy budget Ecological modelling Endemic echinoderm Individual-based model Kerguelen Model sensitivity
Programme: 1044
|
|
|
. (2021). Recent Climate Variability around the Kerguelen Islands (Southern Ocean) Seen through Weather Regimes (Vol. 60). Bachelor's thesis, , .
|
|
|
. (2021). Divergence time and species delimitation of microbivalves in the Southern Ocean: the case of Kidderia species (Vol. 44).
Abstract: The systematics of Subantarctic and Antarctic near-shore marine benthic invertebrates requires major revision and highlights the necessity to incorporate additional sources of information in the specimen identification chart in the Southern Ocean (SO). In this study, we aim to improve our understanding of the biodiversity of Kidderia (Dall 1876) through molecular and morphological comparisons of Antarctic and Subantarctic taxa. The microbivalves of the genus Kidderia are small brooding organisms that inhabit intertidal and shallow subtidal rocky ecosystems. This genus represents an interesting model to test the vicariance and dispersal hypothesis in the biogeography of the SO. However, the description of Kidderia species relies on a few morphological characters and biogeographic records that raise questions about the true diversity in the group. Here we will define the specimens collected with genetic tools, delimiting their respective boundaries across provinces of the SO, validating the presence of two species of Kidderia. Through the revision of taxonomic issues and species delimitation, it was possible to report that the Antarctic species is Kidderia subquadrata and the species recorded in the Subantarctic islands Diego Ramirez, South Georgia and the Kerguelen Archipelago is Kidderia minuta. The divergence time estimation suggests the origin and diversification of Kidderia lineages are related to historical vicariant processes probably associated with the separation of the continental landmasses close to the late Eocene.
Programme: 1044
|
|
|
. (2021). Is the southern crab Halicarcinus planatus (Fabricius, 1775) the next invader of Antarctica? (Vol. 27).
Keywords: climate change establishment niche modelling non-native species reptant crab Southern Ocean survival thermotolerance
Programme: 1044
|
|