Accumulated contaminants are released into the ocean as the ice thaws, refreezes, and thaws again. The marginal ice zone is the southernmost limit of the zone with concentrated ice floes. It is a region with intense biologic productivity, providing the food source for much of the Arctic marine food chain. Glaciers Glaciers are large masses of ice that flow under their own weight. They form when enough snow accumulates to compress the lower layers and form ice.
Some glaciers formed on land move downslope to where they meet the sea.
Along the Greenland coast, outlet glaciers flow from the ice sheet to the sea. Glaciers terminating in the sea periodically break off, or calve, forming icebergs. Icebergs differ from sea ice because they are made up of ice that formed originally from snow, so they do not contain sea salt. Also, because they break off from glaciers, they are generally much thicker than sea ice, sometimes extending more than 100 meters below sea level. Although there are numerous glaciers in Canada, relatively few reach the sea and produce icebergs.