Observing floe-scale sea ice motion in the Greenland Sea marginal ice zone during summer

Abstract

The Fram Strait is a key region for ice export, linking the Arctic with the world ocean. We present floe-scale observations of sea ice motion in the Fram Strait marginal ice zone (MIZ) derived from moderate-scale optical imagery spanning the 2003-2020 period. Tracked ice floes provide Lagrangian measures of ice motion during the spring and summer. We show that the floe size distribution affects the rotation rates and fluctuating velocities of sea ice floes. Using simulations based on a quasi-geostrophic ocean model and a discrete element sea ice model, we show that ocean eddy forcing alone can produce the distinct non-Gaussian velocity anomaly distributions seen in observations. The scale of the velocity distributions decreases with increasing floe size and with increasing distance from the ice edge. Similarly, we show that the rotation rate distribution in both observations and simulations narrows with increasing floe size. Finally, we show that the deformation rates measured from tracked MIZ ice floes reproduce the power law scaling seen in the central Arctic, with the deformation rate decreasing as the scale of observations increases. The observations presented here provide a new avenue for sea ice model development and validation in the summer MIZ.