Though the Arctic Ocean and Hudson Bay are covered in sea ice almost every winter, other peripheral seas vary widely in the extent of sea ice from year to year.
At the end of summer (September), only the multi-year ice at the very center of the Arctic Ocean remains unmelted. This region of multi-year ice is composed of several ice massifs, whose extent and locations vary widely from year to year. In some years the area of sea ice draws closer to the Siberian coast, at others to the Canadian or Alaskan coast. Operations to maintain the safety of the NSR require monitoring and assessment of these trends. In the example illustrated in the image below (September 1986), we can see that multi-year ice reached both coasts of Severnaya Zemlya and Wrangel Island, and an ice massif with higher concentration appeared off the coast of Novaya Zemlya.
3.2.5 Ocean Currents and Ice Drifts in the Arctic Ocean
Although few wide-area observations of ocean currents in the Arctic Ocean are currently available, it is clear that the surface layer and intermediate layer behave in different ways.
Two main currents exchange water between the Arctic Ocean and the world's other oceans through the Fram Strait. The West Spitsbergen Current is a northward-flowing extension of the Norwegian-Atlantic current, which is itself a branch of the Gulf Stream. As it reaches the Arctic Ocean this current sinks below the Arctic surface water to transform into the intermediate water layer, flowing along the Eurasian continental shelf into the inside of the Arctic Ocean. At the center of the ocean this current winds around to the north coast of Canada and flows in the same direction as the surface current of the Arctic Ocean.
One of the prominent surface currents in the Arctic Ocean is a low-velocity current rotating clockwise around the mid-point between the north coast of Alaska and the North Pole. The outer flow of the current has higher velocity and more constant direction than the inner flow has. The direction of the inner flow is less stable. The sea ice drifts on these currents, which are collectively known as the Beaufort Gyre. On the Siberian side, the Beaufort Gyre flows from the Bering Strait to the Fram Strait. Nansen's Fram and most of the vessels that were firmly beset in the polar ice drifted on this gyrating current.
On the Siberian continental shelf a current flows from west to east.
