Sea Ice Formation

The formation of sea ice in the polar oceans plays a major role in the forcing of the Earth's climate.  Sea ice extent varies by 6 million km² in the Arctic and by 18 million km² in the Antarctic.  This solidification of saline ocean water leads to the expulsion of salty brine, the density of which is a driving force for large-scale oceanic currents.  The micro-physical processes involved in the solidification of sea water (or in fact any binary solution) control both the rate of solidification and the rate at which brine is expelled, thus effecting the forcing of oceanic currents.

At the heart of the matter we note that the ice which forms from sea water is essentially pure, and so sea ice is a porous medium saturated with a salty residual brine.  In order for this salty, and therefore dense, brine to drain from this porous medium the sea ice must first grow to a critical thickness, thus accumulating enough interstitial brine to overcome the viscous drag of the matrix.  We have found in the experiments described below that this drainage of brine can be enhanced in the presence of a shear flow external to the sea ice.

Aspects of sea ice formation I am currently interested in can be accessed by clicking on the linked pictures below.

  Interaction of sea ice and shear flows 

  Frost flower formation

  Solidification of binary droplets (NH₄Cl droplet, CuSO₄ droplet)

This research is conducted with John Wettlaufer in the Fluid Dynamics Laboratory at Yale.