Sea ice dynamical response to small and medium scale ocean currents

Sea ice motion arises due to the competing effects of atmospheric, oceanic, and internal ice stresses. We examine ice motion in the East Greenland Marginal Ice Zone and Fram Strait using two new observational datasets: a large ensemble of ice tracker buoys deployed during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, and ice floe trajectories retrieved from moderate-resolution optical imagery detected using the Ice Floe Tracker algorithm. Together, these data reveal abrupt changes in ice dynamic regimes at multiple temporal and spatial scales that coincide with changes in ocean bathymetry. The buoy drift trajectories show decreasing spatial correlation at scales of 1-100 km as the ice breaks up and decreases in concentration during the passage through the Fram Strait. Subdaily sea ice velocity variability shows enhanced spectral power at tidal and inertial frequencies, with clear differences between bathymetrically-defined regions, indicating a major role for submesoscale ocean variability in ice dynamics. Ice drift speed is enhanced along the East Greenland continental shelf break, consistent with forcing from the East Greenland Current, resulting in shear-dominated deformation. The observations demonstrate the importance of small-to-moderate scale ocean currents for understanding and modeling sea ice motion and deformation.