Effects of Boundary Layer Shear on the Morphology of Sea-Ice

Shear flow in the sub ice boundary layer has been shown theoretically to induce a Bernoulli pressure variation which drives a morphological instability of the ice/liquid interface. We investigate this process through an analogue to sea-ice system; the controlled solidification of an ammonium chloride solution in a laboratory flume. We observe the growth of ``sea-ice'' in the presence of a range of geophysically realistic flow speeds and find a threshold speed above which a spatiotemporal variation of the phase fraction of the layer appears. Upon removal of the external flow, the material returns to a uniform state. We describe the systematics of the instability and its importance to the formation of sea ice and associated salt fluxes.