[Update September 26: See this video from the ever-excellent greenman3610 which gives a good overview of the topic]
The Associated Press reported on Monday that thousands of walrus cows have beached in North West Alaska because of the rapid loss of ice this summer in the Chukchi Sea. This is a very rare event but it has been recorded twice before, in 2007 and 2009. Beaching has also been reported on the Siberian side of the sea.
Joseph Romm has a more in-depth posting about this in which he discusses the implications for the regional walrus populations. Of particular concern is the fate of walrus pups, which rely on their mothers’ milk for the first two years of life and cannot fend for themselves. There are reliable reports of pups being stranded in open water where they could not possibly survive, after being separated from their mothers during the rapid thaw.
The walrus populations are also potentially endangered by oil exploration in the area, and the US government is considering adding the walrus to the endangered species list. The USGS maintains a web page where you can find out about the Alaska Science Center’s work on tracking the walrus populations.