Laboratoire Matière et Systèmes Complexes

Jérôme Weiss, IsTerre, Laboratoire de Glaciologie et de Géophysique de l’Environnement, CNRS, Université Joseph Fourier, Grenoble

The role of mechanics on Arctic sea ice decline

Abstract : Sea ice is a very thin layer (a few meters thick at most) of ice forming at the surface of boreal and southern oceans over millions of km². It derives, deforms and fractures under the action of winds, surface currents, and the Coriolis effect. Despite its thinness, it strongly affects the exchanges of energy and momentum between the ocean and the atmosphere, and thus plays an important role in regulating the global climate. In the Arctic, sea ice is undergoing for several decades a dramatic decline both in terms of spatial extent and average thickness. The classical explanation for this decline is accelerating the "Melting Ice" as a result of global warming. This scenario, however, is insufficient to explain the rapidity of this decline. In this presentation, I will show that mechanical processes likely play a key role in this recent evolution. A detailed analysis of sea ice kinematics from passive tracers (drifting buoys) allows a characterization of sea ice brittle behavior, and highlights spectacular evolutions of these mechanical properties : acceleration of drift and deformation, mechanical weakening, .., all these mechanisms reinforcing the "melting ice".