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Title |
Radar altimeter waveform simulations in Antarctica with the Snow Microwave Radiative Transfer Model (SMRT) |
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Journal |
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Year |
2021 |
Publication |
Remote Sensing of Environment |
Abbreviated Journal |
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Volume |
263 |
Issue |
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Pages |
112534 |
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Keywords  |
Antarctic ice sheet Field measurements Modeling Radar altimetry Remote sensing SMRT Waveform |
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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. |
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1110 |
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0034-4257 |
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yes |
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7997 |
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Year |
2021 |
Publication |
Antarctic Science |
Abbreviated Journal |
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Volume |
33 |
Issue |
1 |
Pages |
103-115 |
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Keywords |
Antarctic Cold Reversal glacier fluctuations Holocene in situ cosmogenic chlorine-36 dating palaeoclimate sub-Antarctic |
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1048 |
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0954-1020, 1365-2079 |
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yes |
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8186 |
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Title |
Untangling local and remote influences in two major petrel habitats in the oligotrophic Southern Ocean |
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Journal |
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Year |
2021 |
Publication |
Global Change Biology |
Abbreviated Journal |
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Volume |
27 |
Issue |
22 |
Pages |
5773-5785 |
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Keywords |
Antarctic Circumpolar Current (ACC) biogeography conservation grey petrels high seas hotspot open ocean primary productivity Procellaria cinerea seabirds |
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Abstract |
Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current transports properties across ocean basins through both advection and mixing. Recent tracking studies have indicated the existence of two large-scale, open ocean habitats in the Southern Ocean used by grey petrels (Procellaria cinerea) from two populations (i.e., Kerguelen and Antipodes islands) during their nonbreeding season for extended periods during austral summer (i.e., October to February). In this work, we use a novel combination of large-scale oceanographic observations, surface drifter data, satellite-derived primary productivity, numerical adjoint sensitivity experiments, and output from a biogeochemical state estimate to examine local and remote influences on these grey petrel habitats. Our aim is to understand the oceanographic features that control these isolated foraging areas and to evaluate their ecological value as oligotrophic open ocean habitats. We estimate the minimum local primary productivity required to support these populations to be much <1% of the estimated local primary productivity. The region in the southeast Indian Ocean used by the birds from Kerguelen is connected by circulation to the productive Kerguelen shelf. In contrast, the region in the south-central Pacific Ocean used by seabirds from the Antipodes is relatively isolated suggesting it is more influenced by local factors or the cumulative effects of many seasonal cycles. This work exemplifies the potential use of predator distributions and oceanographic data to highlight areas of the open ocean that may be more dynamic and productive than previously thought. Our results highlight the need to consider advective connections between ecosystems in the Southern Ocean and to re-evaluate the ecological relevance of oligotrophic Southern Ocean regions from a conservation perspective. |
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109 |
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1365-2486 |
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yes |
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Serial |
8258 |
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Author |
Christophe Sauser, Karine Delord, Christophe Barbraud |
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Title |
Demographic sensitivity to environmental forcings: a multi-trait, multi-colony approach |
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Year |
2021 |
Publication |
Oikos |
Abbreviated Journal |
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Volume |
130 |
Issue |
6 |
Pages |
943-957 |
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109 |
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1600-0706 |
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1600-0706 |
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yes |
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Serial |
8039 |
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Author |
Richard D. Ray, Bryant D. Loomis, Victor Zlotnicki |
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Title |
The mean seasonal cycle in relative sea level from satellite altimetry and gravimetry |
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Year |
2021 |
Publication |
Journal of Geodesy |
Abbreviated Journal |
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Volume |
95 |
Issue |
7 |
Pages |
80 |
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Keywords |
Annual geocenter motion Annual land motion Annual/semiannual cycle Satellite altimetry |
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Programme |
688 |
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1432-1394 |
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yes |
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8610 |
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Title |
Similar circling movements observed across marine megafauna taxa |
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Year |
2021 |
Publication |
iScience |
Abbreviated Journal |
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Volume |
24 |
Issue |
4 |
Pages |
102221 |
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Keywords |
Animals Biological Sciences Ecology Ethology Zoology |
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Abstract |
Advances in biologging technology have enabled 3D dead-reckoning reconstruction of marine animal movements at spatiotemporal scales of meters and seconds. Examining high-resolution 3D movements of sharks (Galeocerdo cuvier, N = 4; Rhincodon typus, N = 1), sea turtles (Chelonia mydas, N = 3), penguins (Aptenodytes patagonicus, N = 6), and marine mammals (Arctocephalus gazella, N = 4; Ziphius cavirostris, N = 1), we report the discovery of circling events where animals consecutively circled more than twice at relatively constant angular speeds. Similar circling behaviors were observed across a wide variety of marine megafauna, suggesting these behaviors might serve several similar purposes across taxa including foraging, social interactions, and navigation. |
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394 |
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ISSN |
2589-0042 |
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yes |
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8095 |
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Title |
The early life of king penguins: ontogeny of dive capacity and foraging behaviour in an expert diver |
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Year |
2021 |
Publication |
The Journal of Experimental Biology |
Abbreviated Journal |
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Volume |
224 |
Issue |
12 |
Pages |
jeb242512 |
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Keywords |
Animals Behavior, Animal Bio-logging Diving Feeding Behavior Foraging proficiency Ontogeny Seabirds Spheniscidae Temperature Wiggles |
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137,394 |
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Bachelor's thesis |
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ISSN |
1477-9145 |
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yes |
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8473 |
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Title |
Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago |
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Year |
2021 |
Publication |
Scientific Reports |
Abbreviated Journal |
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Volume |
11 |
Issue |
1 |
Pages |
11917 |
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Keywords |
Animal migration Behavioural ecology Ecology Stable isotope analysis |
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Abstract |
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Programme |
1041 |
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ISSN |
2045-2322 |
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2045-2322 |
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yes |
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8180 |
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Author |
Pauline Goulet, Yan Roper-Coudert, Christophe Guinet |
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Title |
Using on-animal sensors to study the Ocean and its inhabitants |
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Peer-reviewed symposium |
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2021 |
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Keywords |
Animal Distribution Bio-logger Bio-logging Drones & Cap' |
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Abstract |
Bio-logging is a methodological approach in which miniature data recording devices are temporarily attached to free-ranging animals to monitor their movement, behaviour and physiology, as well as the physical parameters of the environment directly surrounding the animals, turning them into bio-plateformes. Unsurprisingly bio-logging emerged from marine and polar studies where the monitoring of individuals in these harsh and remote places cannot be done using traditional approaches. Miniaturization and technological advances has meant that the range of species that can be instrumented, as well as the diversity of the questions that can be sought through bio-logging, are expanding fast. New sensors are constantly being developed, pushing further the limits of this field. Instrumented animals deliver information not only on their activities but also on the physical characteristics of the environments they go through. For instance, over the last two decades, loggers attached to deep diving seals have supplemented physical oceanographic measurements with hydrographic profiles from CTD loggers but also with new series of biological measurements. For examples, fluorescence and light sensors provided information on the concentration of phytoplankton in the euphotic layer; miniature echo sounders together with high sensitivity and fast responding light sensor to detect bioluminescence, brought considerable progress in detecting small size particles (>1-2 mm) such as marine snow, zooplankton, but also fish and squids and estimate their abundance. |
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1201 |
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yes |
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8739 |
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Title |
How king penguins advertise their sexual maturity |
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Journal |
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Year |
2021 |
Publication |
Animal Behaviour |
Abbreviated Journal |
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Volume |
177 |
Issue |
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Pages |
253-267 |
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Keywords |
animal communication mate choice optimal response index ornamentation penguin sexual maturation vocalization |
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137,354 |
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Bachelor's thesis |
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0003-3472 |
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yes |
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Call Number |
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Serial |
7949 |
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