Saint Petersburg, Russia
Saint Petersburg, Russia

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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.


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.


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.


Kirpotin S.,Tomsk State University | Polishchuk Y.,Ugra State University | Bryksina N.,Ugra State University | Sugaipova A.,Ugra State University | And 9 more authors.
International Journal of Environmental Studies | Year: 2011

Palsa peatlands occupy extensive areas in Western Siberia which is one of the most paludified flat lowlands of the world. Climatic changes in Western Siberia are more dramatic compared with other northern regions, and changes in palsa landscapes are more notable due to the severe continental climate here. The distribution, peculiarities and climate-indication capacities of West Siberian palsas are poorly known outside Russia. Thus, Western Siberia is one of the most interesting vast natural polygons for studying climate-driven changes in the landscapes. This paper aims to fill the gap in knowledge on West Siberian palsas and their capacity as a climate regulator. We present issues in distribution, typology and cyclic development of palsa peatlands and their actual climate-driven changes. We also analyse the role of palsas in the atmospheric cycle of CO 2, and the hydrology of the palsa regions. © 2011 Copyright Taylor and Francis Group, LLC.


Zakharova E.A.,Toulouse 1 University Capitole | Zakharova E.A.,French National Center for Scientific Research | Zakharova E.A.,State Oceanography Institute | Kouraev A.V.,Toulouse 1 University Capitole | And 11 more authors.
Journal of Hydrometeorology | Year: 2011

The paper aims to quantitatively estimate the role of snowmelt in the spring flood flow and the redistribution of river runoff for the northern (Arctic) part of the western Siberian Plain (the rivers Poluy, Nadym, Pur, and Taz). In this region, the presence of wetlands and thermokarst lakes significantly influences the seasonal redistribution of river discharge. First the study region is described, and the snow regime from in situ observations at the Tarko-Sale meteorological station is analyzed. As Special Sensor Microwave Imager (SSM/I) estimates of snow depth for this region are lower than in situ observations, a correction of the SSM/I snow depth estimates is done using snow parameters measured on the snow transect near the meteorological station Tarko-Sale for 1991-96. This reestimated snow depth is then used to assess the volume of water stored every winter on the watersheds for 1989-2006. This snow product is compared with the spring flood streamflow estimated from in situ observations, and the regional relationship between the snow water storage and flood flow is constructed. The proportion of meltwater that does not reach the main rivers and is thus evaporated or stored by the wetlands is estimated to be on average 30% (varying from 0% to 74%). We observe an increasing trend of this value from 20%-30% in the early 1990s to 50%-60% in the mid-2000s. This increase could be attributed to several factors such as increased air temperature (leading to increased evaporation, changes in vegetation cover, and active layer depth) and also to human activity. © 2011 American Meteorological Society.


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).


Guerreiro K.,French National Center for Space Studies | Fleury S.,French National Center for Space Studies | Zakharova E.,French National Center for Space Studies | Zakharova E.,State Oceanography Institute | And 3 more authors.
Remote Sensing of Environment | Year: 2016

The scattering properties of the radar signal at Ka and Ku-band frequencies are investigated using a theoretical model and snow grain observations obtained during previous field campaigns. Our results show that the combination of radar altimeters operating at these two frequencies should allow for the retrieval of snow depth over Arctic sea ice. We estimate uncertainties of the ice surface position in relation to crossover observations over sea ice and show that the accuracy of the crossover methodology with short time gap (3 days or less) is better than 3 cm. Comparison of the CryoSat-2/AltiKa retrieved snow depth with in situ measurements provided by Operation IceBridge shows a good agreement with a Root Mean Square Error (RMSE) of 5 cm. Analysis of the CryoSat-2/AltiKa retrieved snow depths over three winters (2013–2015) reveals a thinner snow cover on both Multi-Year (32%–57%) and First-Year Ice (63%–75%) relative to the 1954–91 Warren climatology, suggesting the need for more contemporary year-round and basin-scale snow depth fields. © 2016 Elsevier Inc.


Kouraev A.V.,French National Center for Space Studies | Kouraev A.V.,Tomsk State University | Zakharova E.A.,French National Center for Space Studies | Zakharova E.A.,State Oceanography Institute | And 5 more authors.
Limnology and Oceanography | Year: 2016

Observations of giant ice rings on Lake Baikal (Russia) have recently sparked scientific and public interest. However, there is still no clear consensus on their origins. Here, we provide an inventory of the ice rings based on satellite imagery and photography for 1974-2014. We have identified 45 rings on Lake Baikal (compared with 13 previously known) and also for the first time four rings for the neighbouring Lake Hovsgol (Mongolia). The results of our hydrographic surveys beneath the ice rings in Lake Baikal in 2012-2014 and in Lake Hovsgol in 2015 show the presence of warm double-convex lens-like eddies before and during manifestation of ice rings. We suggest that these eddies are the driving factor for the formation of ice rings in these lakes. We reassess the existing hypotheses of ice ring formation and discuss the potential mechanisms of eddy formation. © 2016 Association for the Sciences of Limnology and Oceanography..


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.


Zakharova E.A.,University Paul Sabatier | Zakharova E.A.,State Oceanography Institute | Kouraev A.V.,University Paul Sabatier | Kouraev A.V.,Tomsk State University | And 3 more authors.
Journal of Hydrology | Year: 2014

Boreal wetlands play an important role in the global water and carbon cycle but their water regime is far from being well understood. The aim of this paper is to study wetland hydrological regime over the 21 mid-size watersheds of the Western Siberia - one of the most bogged regions of the world. By using ENVISAT RA-2 radar altimetry data we analyze seasonal variability of wet zones extent, water level and storage in wetlands. We have identified three main types of wetland water regime characterized by: (1) spring inundation and following deep drainage with/without secondary peak in autumn; (2) spring inundation and low summer variation; (3) spring inundation with medium summer drainage and second autumnal peak. Our estimates show that the floodplain inundation contributes less than 8% to the total wet zones extent. Analysis of the timing of melt and freeze onset and other specific phases of hydrological regime has been done. It was found that the spring inundation lasts for almost 2. months with a latitudinal gradient of melt onset of 8. days/2°. No considerable latitudinal gradient has been found for dates of full freeze onset. Our results show that seasonal amplitude of water level variation for northern part of Western Siberia from altimetry is 0.7-1.5. m for lakes and 0.2-0.5 m for bogs. This represents seasonal variation of wetland water storage of 480. mm for non-permafrost and 130 mm for permafrost-affected zones. © 2014 Elsevier B.V.

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