The ice extent in summer has declined while in winter it hasn't changed much, but both summer and winter ice is getting thinner, and this changes the heat flux in the Arctic. The surface albedo of the ice depends on the extent of melt ponds making these a key feature. Roughness, both at the top and bottom surfaces of the ice, is also important. Ice acts as a conveyor and the provider of key feedbacks to climate through atmospheric and oceanic circulation. The Role of Sea Ice in Habitat Polynyas are openings in the ice that occur when winds blow the ice away from the shore.
Polynyas are highly productive areas biologically.
The ice edge is also very important from a habitat standpoint because fish and whales follow the ice edge. Shelf mixing is also significant because that is how nutrients and pollutants are transported around the Arctic. For example, after an oil spill, oil is sucked into the ice, rests in a layer there, and forms oil ponds in the melt water pools which are then distributed around the Arctic through shelf mixing. The Economic Role of Sea Ice Sea ice has a large effect on navigation because in the Arctic re-supply is accomplished almost entirely by ship. Economically valuable fisheries and whaling are extremely connected to sea ice because, as mentioned above, fish and whales follow the ice edge.