ALT A schematic showing swirling ocean currents (in a white-to-blue/purple colourmap) in the background, with a few sea ice floes overlayed on top, coloured (in a white/cyan-to-red colourmap) by the intensity of boundary-layer turbulence. A very large floe, labelled I, spans across the ocean currents and is mostly red (high turbulence). A few smaller floes, labelled II, are smaller than the scales of the variability in the currents and are mostly white/cyan (low turbulence). A second set of similarly sized small floes, labelled III, are colliding with the large floe and are the same red colour (high turbulence).