Studying the Arctic Ocean’s freshwater budget by seeing under the ice from space

摘要

The Arctic Ocean represents just 4.3 of the global ocean area, making it the smallest of the world’s major ocean divisions. It is largely enclosed by land, limiting interactions with the global ocean, and sea ice, which covers between 5 x 106 km~2 (in summer) and 15 x 10~6 km~2 (in winter), acts as a barrier between the ocean and the atmosphere. This sea-ice barrier not only limits the exchange of heat between the atmosphere and ocean, it also limits the exchange of momentum, which results in relatively low surface current speeds. Further, the Arctic Ocean surface layer stores a large amount of cool and buoyant freshwater (somewhere in the region of 80 000-90 000 km~3) in the form of both ice and liquid; cool, low salinity water overlies warmer, more saline water at depth, and the resulting stratification limits vertical mixing between the surface and deep ocean, preventing momentum transfer from the surface to the deep ocean, but also preventing upward mixing of heat from depth (there is enough heat in the deep Arctic Ocean to melt the Arctic sea ice several times over).