Arctic sea-ice cover has been steadily thinning for years, according to satellite measurements since 1979. In March 2017, when ice cover should have been near its maximum, the U.S. National Snow and Ice Data Center reported that Arctic sea-ice extent was the lowest in the 38-year satellite record. Ice-cover thinning has been attributed to warming Arctic air temperatures, but that may not be the only factor melting the ice, according to a recent study. Researchers reported in the journal Science (April 2017) that on the Atlantic side of the central Arctic Ocean Basin (that is, the Eurasian Basin), warm water from the Atlantic Ocean is melting the sea ice from below. See also: Arctic Ocean; Global climate change; Remote sensing; Sea ice
From 2002 to 2015, Arctic researchers moored sensors at various depths below the Eurasian Basin sea ice to measure temperature and salinity. The researchers found that over time, the cold and dense salty barrier (cold halocline layer or CHL) that normally keeps warm Atlantic water at about 100 meters below the sea ice had been growing thinner and eventually began disappearing in the winter because of changes in temperature and salinity of surface waters. As a result, the researchers now attribute decreased winter sea-ice formation in the Eurasian Basin equally to atmospheric warming and ocean heating. See also: Mixed layers (oceanography); Ocean circulation; Seawater
