Wednesday, 1 May 2013: 10:30 AM
South Room (Renaissance Seattle Hotel)
There has been a sequence of six warm, substantially sea ice-free summers in the Beaufort Sea beginning in 2007 that herald a new normal in Arctic climate; 2012 had an 18% decrease in northern hemisphere summer sea extent compared to the previous record in 2007, but the geographic focus was further east in the eastern Beaufort Sea and was more related to the presence of thin sea ice rather than extreme weather. While the overall thinning of the Arctic sea ice pack is due in part to global climate change, there are additional regional coupled air-sea ice-ocean interactions that contribute to a further Arctic Amplification. The Beaufort Sea south of 76° N has been absorbing almost double the amount of shortwave radiation over the last five years than in the past, roughly enough to melt 1.5 x 106 km2 of 1 m thick sea ice each year. The consequence of this heating was revealed by waveglider and satellite measurements of 6-10 C ocean temperatures in the upper 6 meters during summer 2011, perhaps the largest temperature anomalies of the Northern Hemisphere. The causes of the unusual Beaufort weather pattern of the summers of 2007-2011 may relate to increased atmospheric pressure over North America and Greenland. The added upper ocean warmth means a late start to ice formation in the fall, and hence anomalous heating of the atmosphere. This added heating disrupts the Arctic atmospheric circulation causing regional atmospheric flow meanders potentially causing extreme weather events, as persistent Arctic climate change interacts with chaotic mid-latitude atmospheric dynamics.
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