HR: 0800h
AN: C11B-0438    [Abstracts]
TI: Evidence for Significant Acceleration of Arctic Sea Ice Drift over the last 25 Years
AU: * rampal, p
EM: prampal@lgge.obs.ujf-grenoble.fr
AF: LGGE-CNRS, 54 Rue Moliere, Saint Martin d'Heres, 38402, France
AU: weiss, j
EM: weiss@lgge.obs.ujf-grenoble.fr
AF: LGGE-CNRS, 54 Rue Moliere, Saint Martin d'Heres, 38402, France
AU: Marsan, d
EM: david.marsan@univ-savoie.fr
AF: LGIT, Universite de Savoie, Le Bourget du Lac, 73376, France
AB: The Arctic sea ice cover is undergoing significant climate-induced changes, affecting both its extent and thickness. This arctic sea ice decline is generally attributed to a thermodynamic effect of warmer surface air temperatures enhanced by a positive feedback loop involving albedo. In this context, sea ice shrinkage is associated with a climate change particularly intense in the Arctic. Here we show that this change in the sea ice cover is also accompanied by an acceleration of the average sea ice drift over the last 25 years. We performed an analysis of the Arctic sea ice drift from the buoys trajectories of the IABP dataset between 1979 and 2006. A strong seasonal variability of the sea ice mean drift is revealed, out of phase with respect to the sea ice extent seasonal variability, i.e. with a maximum average velocity occurring in October and a minimum in April. Averaging sea ice drift over the summer months, we observed a significant increase of the mean velocity over the whole Arctic basin at a rate of +10 percent per decade. Such acceleration is also observed in winter (+15 percent per decade). The associated standard deviations of the drift velocities, which are proxies of sea ice dispersion at large spatial and time scales and consequently of sea ice deformation (Rampal et al., 2007), are also increasing significantly over the period. This acceleration of sea ice drift and deformation might suggest that sea ice dynamics intervenes in the albedo feedback loop: larger deformation implies an increasing sea ice fracturing, i.e. more open water and therefore a decreasing albedo. This will accelerate sea ice thinning in summer and delay refreezing in early winter, therefore decreasing the mechanical strength of the cover and allowing more fracturing and larger drift and deformation.
DE: 0750 Sea ice (4540)
DE: 0762 Mass balance (1218, 1223)
DE: 0774 Dynamics
SC: Cryosphere [C]
MN: 2007 Fall Meeting