Synoptic Drivers of Observed Wave States in Southern Chukchi Sea

Two bottom-mounted recording Doppler current profilers (RDCP) were deployed at nearshore locations (approximately 3 and 8 km offshore, in about 18 m water depth) in the southeast Chukchi Sea, Alaska, from October 2009 to September 2010 (UTC) with the goal of linking observed wave activity - wind-sea and swell — to their synoptic drivers. The northerly RDCP recorded a total of 16 events of elevated wave states: 15 exceeding 1 m significant wave height (SWH), and 1 exceeding 2 m SWH. The southerly RDCP recorded a total of 25 events of elevated wave states: 23 exceeding 1 m SWH, 2 m exceeded on two occasions and a SWH of 3 m was observed. Detailed analysis of the three large events (i.e., SWH events >2 m), including comparison with NARR wind data, strongly suggested the wave energy evolved from a distant storm and would be defined as swell. Coastal proximity to the east limited fetch; this was not the case for the west/northwest directions. Wave direction was also westerly, varying about 25 degrees to the north (clockwise) or the south (counterclockwise) from the wind direction which is believed to be influenced by fetch and the strong current flow located where the nearshore RDCPs were deployed. Shore-fast sea ice was shown to dampen wave activity over a 3 month period (January–April 2010), which implies an early ice breakup in this nearshore region. Two events appeared to be driven by southwesterly winds associated with cyclonic systems that moved into the eastern Chukchi Sea and then stalled. However, a third wave event appeared to be driven by northwesterly winds associated with a cyclonic system over the Brooks Range, a less common occurrence. Storm activity is common in the Bering Sea/North Gulf of Alaska at this time of year, as is associated elevated marine-state resopnse.