Atmospheric forcing of wave states in the southeast Chukchi Sea

Abstract

The objective of this study was to assess the impact that the ocean state, particularly ocean waves, have on coastal communities and operations in the Western Alaska region. In situ measurements and one-dimensional spectra models, were used to link observed wave activity – wind-sea and swells – to their synoptic drivers. Bottommounted Recording Doppler Current Profilers (RDCPs) were placed at offshore and nearshore locations in the southeast Chukchi Sea, Alaska, during 2007 and 2009-2010. The highest significant wave height (SWH) “events” were defined as wave heights above 2m and 3m for a duration of 6h or more. Results show that SWH events appeared to be driven by three types of systems, 1) cyclonic systems that moved into the eastern Bering Sea and then stalled there, 2) cyclonic systems that moved into the eastern Chukchi Sea and then loitered there, and 3) a cyclonic system over the Brooks Range, a less common occurrence. Results also show the offshore region having highest SWHs with an east wind and wave direction, and classified as a wind-sea state. For the nearshore region, highest SWHs with south and west wind and wave directions, generally showed a swell state. Agreement between one-dimensional spectral models and in situ measurements was greatest for the higher wind-sea state in the offshore region, while discrepancies arose for the lower swell state in the nearshore region. Cross-validation of in situ measurements with satellite altimeter radar measurements were also conducted. Good correlation was found for the offshore regions iv

but not for the nearshore regions. Satellite observations were also used to assess wave conditions in the Arctic during the years 1993-2011. A 0.020m/year increase of SWH for the SE Chukchi Sea and a 0.025m/year increase for the Pacific-Arctic, was found which correlates well with diminishing sea ice and the heighted wind speed, also shown in this study.