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Seeing the Ocean Through Sea Ice: Signatures of Submesoscale Ocean Flows in Sea Ice patterns in Marginal Ice Zones

Sea ice at low concentrations is a natural surface ocean tracer and hence contains at least partial information about the underlying ocean turbulence. Indeed, during low-wind and cloud-free days, signatures of small scale vortices, filaments, and striations are commonly observed in satellite images of sea ice within marginal ice zones (see figure). However, sea ice is not a passive tracer, and its distribution over regions of strong surface ocean convergence depends on a balance between the driving external ocean drag and the resistive internal stresses due to ice floe interactions. This study explores the key mechanisms that explain the observed sea ice patterns, and relates them to the underlying ocean fronts, filaments, and eddies.

The largest response in sea ice concentrations occurs at relatively low background  concentrations of about 15%--50%. We find that ocean cyclones accumulate sea ice whereas anticyclones repel it; cyclonic ocean filaments, characterized by a strong surface convergence, lead to sea ice accumulation over characteristic time scales of 1-2 days. For nearly nondivergent ocean currents, such as symmetric eddies, the presence of sea ice induces frictional Ekman transport which can act to either concentrate or dilute the sea ice. The ice-induced Ekman transport over cyclonic eddies is able to accumulate the sea ice on daily time scales, implying that submesoscale currents with persistent time scales of several days should appreciably imprint themselves on the sea ice cover. These results suggest that ocean turbulence statistics can be inferred from still satellite images of sea ice in marginal ice zones.