Synoptic forcing of wave states in the southeast Chukchi Sea, Alaska, at nearshore locations

Abstract

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 swells-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 C2 m), including comparison with high-resolution reanalysis wind data (North America regional reanalysis), strongly suggested the wave energy evolved from a distant storm and would be defined as swell. Due to the close proximity of the shoreline to the east of the instruments, wind speeds based on reanalysis were constrained so fetch was westerly. Wave direction was also westerly, varying about 25°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 is also believed to play a role but shown to only dampen wave activity for 3 months (January-April 2010), thus implying 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, the second storm event appeared to be driven by northwesterly winds associated with a cyclonic system over the Brooks Range, a less common occurrence. Given that the typical storm activity in the region occurs as storms move into the Bering Sea in fall, this

Projections of Extreme Ocean Waves in the Arctic and Potential Implications for Coastal Inundation and Erosion

“…Waves are also affected by wave refraction when entering the shallow continental shelf, as, for example, the East Siberian Shelf, which stretches 1,500 km offshore with an average depth of ∼50 m. Note that, according to the Snell's law of linear wave propagation, an offshore wave with, for instance, a T = 15 s entering 50 m deep waters at an angle almost parallel to the isobathymetric lines refracts ∼45° toward the shallower waters. In addition, the NE waves observed in the mid‐southern Chukchi Sea are in agreement with the cyclonic systems formed in the Bering Sea that typically move into the Chukchi Sea during fall (Francis & Atkinson, 2012).…”

Sea Ice

“…Further, increased fetch during the fall storm season has resulted in increases in wave amplitudes in fall (Overeem et al, 2011). Thinner, more dynamic ice also appears to be associated with increases in wave heights and deeper propagation of swell into the ice pack in spring (Francis and Atkinson, 2012). These changes work in concert to increase erosive action, thermal subrosion of coastal permafrost, and thereby accelerate rates of coastal retreat with potentially negative impacts on coastal communities and infrastructure.…”

“…Thus, the potential for greater significant wave heights and a longer open water period with potential for wave action and coastal flooding has been identified in a number of regions, with major impacts in particular in the Siberian and Pacific Arctic sector (Atkinson, 2005;Overeem et al, 2011;Asplin et al, 2012;Francis and Atkinson, 2012). Thus, the potential for greater significant wave heights and a longer open water period with potential for wave action and coastal flooding has been identified in a number of regions, with major impacts in particular in the Siberian and Pacific Arctic sector (Atkinson, 2005;Overeem et al, 2011;Asplin et al, 2012;Francis and Atkinson, 2012).…”