Atmosphere and Ocean Impacts on Recent Western Arctic Summer Sea Ice Melt

Abstract Summer sea ice in the western Arctic, specifically in the Chukchi and Beaufort Seas, has been rapidly declining during the last several decades. Annual minima in six recent Septembers (2007–2012) have witnessed the lowest western Arctic sea ice extents of the modern satellite era. The western Arctic summer sea ice has become less extensive amidst a fundamental transition from once widely prevalent and thick multi‐year ice to a thinner and readily melted first‐year ice cover. Questions remain for the Arctic climate research community involving the combination of factors that may be forcing these negative sea ice trends, particularly as current understanding of these complex ice–climate interactions evolves. Interannual variations of atmospheric pressure systems such as the Beaufort Sea High help determine the overlying wind direction and strength as well as the severity of summer ice cover. Atmospheric circulation teleconnections are important in sea ice variability but the role of some, such as the Arctic Oscillation, may in fact have changed as the western Arctic transitioned to a thinner ice cover. Reductions in summer sea ice extent became noticeable from 1998 onward and can be partly attributed to oceanic warming in the northern Pacific across the Bering Strait into the western Arctic. Warming of the northern Atlantic has had dramatic impacts in the Eurasian Arctic but a viable physical mechanism by which it can produce western Arctic ice melt is not yet established. Arctic warming induced by forcing from greenhouse gases is estimated to rival the impact of atmospheric teleconnections and helps produce the “Arctic amplification” of air temperatures that enhances summer sea ice melt. Late summer open water may in turn be altering the atmospheric circulation, weather and climate of subsequent autumn and winter seasons throughout the middle latitudes.