User requirements for a Copernicus polar mission

To monitor on a continuous basis the vast and harsh Arctic environment, considering the sparse population and the lack of transport links, space technologies are definitely essential tools including Earth observation, navigation and communication satellites. DG GROW asked for an Expert Group in spring 2017 with the mandate to update and/or complete the review and analysis of the Users’ needs, thus allowing the Commission to assess the relevance of the development of a "Copernicus expansion mission" dedicated to Polar and Snow monitoring.JRC.D.6-Knowledge for Sustainable Development and Food Securit

Cycle de l’eau et glaces terrestres

International audienc

Variabilité atmosphérique arctique et globale : amplification, couplages et impacts

International audienc

Un océan en mutation : du milieu physique aux écosystèmes marins

International audienc

Prospective sur le retrait des glaces

International audienc

Variability of the ice export through Fram Strait in 1993–98: the winter 1994/95 anomaly

The origin of the large positive anomaly of the Fram Strait sea ice export which occurred in winter 1994/95 is analysed on the basis of a model simulation of the Arctic sea ice cover over the period 1993–98. The overall intra-annual and interannual variability in the model is in good agreement with observational estimates and the 1994/95 anomaly is well reproduced with an amplitude amounting to half of the mean winter value. Model results suggest that, concomitant to anomalous export velocities, larger than usual ice thickness in the strait contributes to the outstanding amplitude of the anomaly. Analysis on the ice thickness evolution in the strait indicates that the thick ice advected in Fram Strait at the end of the fall of 1994 originates in the anomalous cyclonic wind stress which prevailed during the preceding summer. This anomalous wind stress resulted in persistent convergence of the ice flow against the northern coasts of Canada and Greenland and in the formation of a large thickness anomaly north of Greenland. The anomaly then feeds the Fram Strait ice flow during those following winter months when the local wind forcing in the strait favours ice drift from the north-west. Our results suggest that short-term wind stress variations resulting in local thickness changes to the north of Fram Strait can lead to substantial variability of the Fram Strait ice export

Antarctic shelf circulation: a case study based on summer observations off Adélie Land

International audienc

Response of the eastern North Atlantic subpolar gyre to the North Atlantic Oscillation

International audienceThe salinity changes in the subpolar gyre (SPG) in response to the North Atlantic Oscillation (NAO) are studied in idealized numerical experiments. In the eastern SPG, anomalies of similar amplitude as those observed during the 1995-1996 shift of the NAO are mainly driven by the local response to the wind stress, through the set-up of an anticyclonic "intergyre" anomaly. In positive NAO, this anomalous circulation advects altogether (i) fresh, cold water from the western to the eastern SPG, contributing there to the formation of negative salinity anomalies, and (ii) warm, saline subtropical water to the south of Newfoundland, forming positive anomalies there. The latter are subsequently transported with the North Atlantic Current to the eastern SPG where they could act to weaken the low-salinity signal. The occurrence of this signal is concomitant with the acceleration of the gyre but, in contrast to earlier findings, is not subject to it

Forcing of oceanic heat anomalies by air-sea interactions in the Nordic Seas area

International audienceHydrographic data and atmospheric reanalysis from 1982 to 2005 are used to show a strong link of the Atlantic water temperature (AWT) anomalies observed in the transition zone between the Norwegian Atlantic current and the West Spitsbergen current in summer to the surface heat flux (SHF) anomalies observed over the Barents Sea open water in the preceding late winter. A mechanism proposed for this link is formation of ocean temperature anomalies in a deep mixed layer and their subsequent westward export by a branch of Atlantic water recirculating in the western Barents Sea. The SHF anomalies over the Barents Sea are due to advection of temperature and humidity by anomalous winds across the Arctic ice edge and do not strongly depend on the North Atlantic oscillation (NAO). Correlations of up to about 0.9 between the AWT anomalies and indices of atmospheric variability over the Barents Sea open prospects for seasonal AWT predictability. It is also shown that the wind-forcing responsible for positive AWT anomalies is involved in a cyclonic perturbation of the atmospheric circulation over the Nordic Seas. This perturbation generates, through influence on the sea ice distribution, a lobe of SHF anomalies in the marginal ice zone (MIZ) on the eastern (Barents Sea) and western (Greenland Sea) sides of the Nordic Seas which has the opposite sign to the open water lobe. In contrast to the Barents Sea MIZ, the diabatic heating of the atmosphere by upward SHF anomalies in the Greenland Sea MIZ competes with cold advection

Atmospheric forcing on the Canadian Arctic Archipelago freshwater outflow and implications for the Labrador Sea variability

International audienceThe variability of the freshwater export through the Canadian Arctic Archipelago (CAA) is analyzed using a hindcast simulation forced by surface atmospheric forcing from the ERA40 reanalysis (1958-2001). Although the two channels representing the archipelago in the model are both sensitive to the along-channel sea surface height (SSH) gradient, they appear to have very distinct behaviors. The outflow to Lancaster Sound is shown to be largely controlled by the magnitude of the upstream SSH gradient across McClure Strait. The gradient shows a close link to the wind stress curl in the western Arctic but also to a large-scale SSH anomaly pattern which has a strong signal over the shelf to the south of McClure Strait. The latter has, however, little statistical connection to the SSH variability in the Beaufort Gyre. By contrast, the outflow through Nares Strait responds preferentially to SSH variations in the northern Baffin Bay which are remotely forced by air-sea heat exchanges in the Labrador Sea. The variability is largely coherent between the two outflows and is controlled by a dipolar atmospheric pattern reminiscent of the North Atlantic/Arctic Oscillation. When entering the subpolar gyre, the CAA freshwater outflow remains confined to the Labrador shelf with little impact on the salinity of the interior Labrador Sea and potentially on the convection. The latter is represented by a distinct mode of salinity variability in the western subpolar gyre which is rather influenced by the variability of the sea ice export through Fram Strait