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Garestier F.,University of Caen Lower Normandy | Zakharova E.,French National Center for Scientific Research | Zakharova E.,State Oceanography Institute | Kouraev A.,French National Center for Scientific Research | And 3 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2014

This paper presents an investigation to the estimation of the surface movements over the region of Yakutsk using TerraSAR-X data acquired during two months. The interferometric phase generated from the data stack presents a deterministic behavior over the most of the image, due to short temporal baseline and frozen surface context, and reveals fringes due to surface deformation over different geo-morphologic objects as alluvial deposits, alasses and other thermokarstic depressions, but also on the Lena river. © 2014 IEEE.

Zakharova E.A.,French National Center for Scientific Research | Zakharova E.A.,State Oceanography Institute | Fleury S.,French National Center for Scientific Research | Guerreiro K.,French National Center for Scientific Research | And 5 more authors.
Marine Geodesy | Year: 2015

Sea ice leads play an essential role in ocean-ice-atmosphere exchange, in ocean circulation, geochemistry, and in ice dynamics. Their precise detection is crucial for altimetric estimations of sea ice thickness and volume. This study evaluates the performance of the SARAL/AltiKa (Satellite with ARgos and ALtiKa) altimeter to detect leads and to monitor their spatio-temporal dynamics. We show that a pulse peakiness parameter (PP) used to detect leads by Envisat RA-2 and ERS-1,-2 altimeters is not suitable because of saturation of AltiKa return echoes over the leads. The signal saturation results in loss of 6–10% of PP data over sea ice. We propose a different parameter—maximal power of waveform—and define the threshold to discriminate the leads. Our algorithm can be applied from December until May. It detects well the leads of small and medium size from 200 m to 3–4 km. So the combination of the high-resolution altimetric estimates with low-resolution thermal infra-red or radiometric lead fraction products could enhance the capability of remote sensing to monitor sea ice fracturing. © 2015, Copyright © Taylor & Francis Group, LLC.

Kouraev A.V.,Toulouse 1 University Capitole | Cretaux J.-F.,State Oceanography Institute
Handbook of Environmental Chemistry | Year: 2010

Weaddress spatial and temporal variability of ice conditions in the Aral Sea from historical observations and recent satellite microwave observations. A short description of the historical evolution of the Aral Sea since the mid-twentieth century is given, as well as recent activities related to the dam in the Berg strait. An overview of historical observations of the ice regime at the coastal stations and using aerial surveys is provided. The lack of reliable in situ measurements and time series for ice cover parameters since the mid-1980s may be successfully overcome by using active and passive microwave satellite observations, which provide reliable, regular, frequent, and weather-independent data. An ice discrimination methodology, based on the synergy of active and passive data from radar altimeters TOPEX/Poseidon, Jason- 1, ENVISAT and Geosat Follow-On (GFO) satellites, aswell as the SMMR and SSM/ I radiometers is presented. This methodology has been applied to the entire satellite dataset to define specific dates of ice events (first appearance of ice, formation of stable ice cover, appearance of open water and the complete disappearance of ice) for both the Small Aral and Eastern Large Aral. The resulting time series of ice cover parameters are analysed in the context of available in situ observations. First we complement historical observations by satellite imagery in the visible range to illustrate spatial patterns in ice formation, development and decay prior to the late 1980s and in recent time. Then we address interannual variability of timing of ice events and severity of ice conditions since the earliest coastal observations (1940s) until now (2006/2007). Finally, we discuss temporal variability of ice regime parameters in the context of air temperature, bottom morphology and salinity changes. © Springer-Verlag Berlin Heidelberg 2009.

Gremillet D.,CNRS Center of Evolutionary and Functional Ecology | Gremillet D.,University of Cape Town | Fort J.,CNRS Coastal and Marine Environment Laboratory | Amelineau F.,CNRS Center of Evolutionary and Functional Ecology | And 6 more authors.
Global Change Biology | Year: 2015

Arctic climate change has profound impacts on the cryosphere, notably via shrinking sea-ice cover and retreating glaciers, and it is essential to evaluate and forecast the ecological consequences of such changes. We studied zooplankton-feeding little auks (Alle alle), a key sentinel species of the Arctic, at their northernmost breeding site in Franz-Josef Land (80°N), Russian Arctic. We tested the hypothesis that little auks still benefit from pristine arctic environmental conditions in this remote area. To this end, we analysed remote sensing data on sea-ice and coastal glacier dynamics collected in our study area across 1979-2013. Further, we recorded little auk foraging behaviour using miniature electronic tags attached to the birds in the summer of 2013, and compared it with similar data collected at three localities across the Atlantic Arctic. We also compared current and historical data on Franz-Josef Land little auk diet, morphometrics and chick growth curves. Our analyses reveal that summer sea-ice retreated markedly during the last decade, leaving the Franz-Josef Land archipelago virtually sea-ice free each summer since 2005. This had a profound impact on little auk foraging, which lost their sea-ice-associated prey. Concomitantly, large coastal glaciers retreated rapidly, releasing large volumes of melt water. Zooplankton is stunned by cold and osmotic shock at the boundary between glacier melt and coastal waters, creating new foraging hotspots for little auks. Birds therefore switched from foraging at distant ice-edge localities, to highly profitable feeding at glacier melt-water fronts within <5 km of their breeding site. Through this behavioural plasticity, little auks maintained their chick growth rates, but showed a 4% decrease in adult body mass. Our study demonstrates that arctic cryosphere changes may have antagonistic ecological consequences on coastal trophic flow. Such nonlinear responses complicate modelling exercises of current and future polar ecosystem dynamics. © 2015 John Wiley & Sons Ltd.

Marchenko A.,University Center in Svalbard | Kvamstad B.,Norwegian Marine Technology Research Institute | Fjortoft K.,Norwegian Marine Technology Research Institute | Hoyland K.,University Center in Svalbard | Brazhnikov D.,State Oceanography Institute
Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC | Year: 2011

Data of Iridium Ice tracking buoys Oceanetic Model 703 deployed on drifting ice in the marginal ice zone and on interior drift ice of the West Barents Sea are analyzed. Mean drift velocities are compared with mean wind velocities and prevailing sea currents in the region. Functions of distributions of absolute ice drift velocities, drift directions, volumetric and shear strain are constructed for different intervals of the ice trackers trajectories and analyzed. The trajectories of ice trackers are compared with ice drift trajectories reconstructed by satellite data provided by IFREMER. Copyright © (2011) by Port and Ocean Engineering under Arctic Conditions (POAC 2011).

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