4.2 Trends in the Sea State of the Beaufort and Chukchi Seas

Tuesday, 24 January 2017: 10:45 AM
Conference Center: Skagit 3 (Washington State Convention Center )
Jim Thomson, University of Washington, Seattle, WA; and O. N. R. Sea State team

Analysis of model hindcast data suggests that wave heights and wave periods are increasing in the Beaufort and Chukchi seas over the last two decades.  The increase is attributed to increases in both the duration and extent of ice-free areas during the seasonal cycle.  This signal is strongest in the autumn months, during which storms have become more likely to pass over ice-free areas (and thus generate ocean surface waves).   This trend is applied as context for the field campaign of the Office of Naval Research ‘Sea State and Boundary Layer Physics of the Emerging Arctic’ program[1], which conducted surveys and process studies in the region during a 40 day cruise in autumn 2015.  Consistent with the hindcast analysis, the 2015 signals are dominated by specific events (i.e., storms and/or wind events).  These events cause only a marginal increase in the average wave heights or wave periods of the region; however they cause a significant shift in the probability distributions of these parameters.   The field data from 2015 suggest a tightly coupled system, in which the sea state alters the air-ocean-ice fluxes that control autumn ice advance, and that feeds back on the sea state.  This process, in turn, affects the strength and thickness of the ice that forms, and thus the susceptibility for that ice to melt during the next seasonal cycle. 
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