Wave-driven transport and shear along a sea ice edge

James M Thomson1, Bjoern Lund2, John T. Hargrove3, Jennifer A MacKinnon4, Madison Smith1 and Jochen Horstmann5, (1)Applied Physics Laboratory University of Washington, Seattle, WA, United States, (2)University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL, United States, (3)University of Miami, Center for Southeastern Tropical Advanced Remote Sensing, Miami, FL, United States, (4)Scripps Institution of Oceanography, La Jolla, CA, United States, (5)Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research, Geesthacht, Germany
Surface gravity waves in polar oceans often impinge on the sea ice pack, and can be expected to play a role in shaping the edge of the ice pack. We present observations of oblique surface gravity waves incident from open water onto a compact ice edge in the Beaufort Sea. Significant down-wave transport of sea ice, relative to the interior ice pack, occurs in a 100 m wide zone along the ice edge. Observations include buoy measurements of the incident waves, along with shipboard W-polarized Doppler radar measurement and SAR satellite imagery of the waves and the sea ice motion. Buoy measurements of surface winds and ocean current profiles also are employed. The data were collected in September 2018 as part of the Stratified Ocean Dynamics in the Arctic (SODA) program.

Using an analogy with longshore currents and sediment transport in the surfzone, we evaluate the gradients of the along-ice wave radiation stress across the marginal ice zone. We find that this change in the momentum flux of the waves is sufficient to cause the observed sea ice transport of 0.2 - 0.3 m/s along the ice edge. We assess alternate hypotheses in which the sea ice transport is driven by the wind or mesoscale ocean currents, but the estimated magnitude of these forcings is insufficient. We further explore the potential for shear instabilities along the ice edge, which is related to observed meanders in the ice edge shape.