A Close-Up Look at Arctic Sea Ice: Floe-Scale Observations in the Marginal Ice Zone

Sea ice motion in marginal ice zones (MIZs)—the transition regions between open water and pack ice—is inherently multi-scale. Traditional satellite-derived observations are effective for large-scale ice drift, but lack the resolution to capture floe-scale motion in the MIZ, and have reduced confidence during the melt season. Here, we present the Ice Floe Tracker (IFT) algorithm, developed to automatically acquire Lagrangian observations of floe-scale (1-50 km in size) sea ice translation and rotation, along with geometrical characteristics of tracked floes in the Arctic MIZ. The data is well-suited to characterization of sea ice floe kinematics at daily resolution over interannual to decadal timescales, enabling observation-driven research into the correspondence between the sea ice floe size distribution (FSD) and ice-ocean coupled dynamics. We show that the FSD in the East Greenland Sea MIZ evolves from April to July, with increasing prevalence of small floes. We find inverse correlation between floe size and the variance of rotation rates and of drift speed anomalies. Comparisons to large-scale ice motion and to discrete element model simulations show that deviations from the mean drift resolved by IFT are exponentially distributed, suggesting that IFT is capturing fine-scale variability consistent with underlying ocean turbulence. The IFT data provides new avenues for probing the dynamics of multi-scale granular-type flow in the coupled atmosphere-ice-ocean system.