Historical Changes in the Beaufort-Chukchi-Bering Seas Surface Winds and Waves, 1971-2013

This study characterizes historical changes in surface wind speed and ocean surface waves in the Beaufort-Chukchi- Bering Seas using Environment Canada's Beaufort Wind and Wave Reanalysis for the period 1970-2013. The results show that both the significant wave height ( Hs) and mean wave period ( T-m) have increased significantly over the Bering Sea in July and August and over the Canadian Beaufort Sea westward to the northern Bering Sea in September, and that the 1992-2013 trends in September mean Hs agree well with satellite-based trend estimates for 1993-2010. Most outstandingly, the regional mean Tm has increased at a rate of 3%-4% yr 21 of the corresponding 1970-99 climatology; it has more than tripled since 1970. Also, the regional mean Hs has increased at a rate of 0.3% to 0.8% yr 21. The trends of lengthening wave period and increasing wave height imply a trend of increasing wave energy flux, providing a mechanism to break up sea ice and accelerate ice retreat. The results also show that changes in the local wind speeds alone cannot explain the significant changes in waves. The wind speeds show significant increases over the Bering Sea to the north of Alaska in July and over the central part of the domain in August and September, with decreases in the region off the Canadian coasts in August. In the region west of the Canadian coast, the climatological mean wind direction has rotated clockwise in July and August, with the climatological anticyclonic center being displaced northeastward in August.