Ice-covered sea areas in the Arctic Ocean during summer have nearly halved since the 1970s and 1980s, raising alarm that the ocean is shifting from a multiyear to a seasonal ice zone. The Intergovernmental Panel on Climate Change (IPCC) has forecasted summer ice cover in the polar ocean might disappear almost completely as early as 2050. Various factors have been cited as causes, including rising temperatures and changes in atmospheric circulation patterns.