Lead (sea Ice) - Ice Formation in Leads

Ice Formation in Leads

Once a crack occurs within the ice cover and begins to expand to make up a lead, the open water inside the lead is exposed to the cold air temperatures and will freeze. Because wind fetch inside a lead is typically very short, wave action is considerably reduced. Ice growth therefore takes place in a low energy regime environment. Following a stage of frazil ice formation, which sometimes results from seeding by snow crystals, the resulting thin ice skim is followed by the growth of congelation ice. In windier regions, as in the Southern Ocean, frazil ice accumulation may occur along the downwind side of leads. If the ice on that side is thin, the frazil may be driven below that ice (resulting in a complex interlayering pattern). Leads have an impact on global water circulation. As ice begins to form inside a lead, it incorporates some of the salt in the seawater (which is why sea ice is saline) but rejects most of it. This brine then sinks, inducing convective processes in the water column below.