Séminaire
Arctic sea ice continues to melt at an unprecedented rate that is commonly underestimated by climate projection models. This may imply biases in the representation of physical processes that bring heat to the sea ice in these models. In this talk I will identify interactions between ocean-ice heat fluxes, sea ice cover, and upper-ocean eddies that constitute a positive feedback missing in climate models. Using an eddy-resolving global ocean model, I will demonstrate that ocean-ice heat fluxes are predominantly induced by localized and intermittent ocean eddies, filaments, and internal waves that episodically advect warm subsurface waters into the mixed layer where they are in direct contact with sea ice. Additionally, under-ice eddy energetics are critically modulated by frictional dissipation in ice-ocean boundary layers, being dominant under consolidated winter ice but substantially reduced under low-concentrated weak sea ice in marginal ice zones. These results indicate that the Arctic sea ice loss must be reducing upper-ocean dissipation and hence, at least transiently, producing more energetic eddies and amplified ocean-ice heat exchange. The study emphasize the need for sea ice-aware parameterizations of eddy-induced ice-ocean heat fluxes in climate models.
juliette.mignot@locean-ipsl.upmc.fr