The Circulation Structure Around Hanna Shoal on the Northeastern Chukchi Sea Shelf

Year-round moorings were deployed across the 40, 50, and 56 m isobaths northwest and northeast of Hanna Shoal to investigate circulation patterns and flow structure from September 2012 through September 2014. The results indicate a mean clockwise circulation of deep (>30 m) waters at depth, which was more apparent in the first year of deployment. Near surface currents were westward at ~4 cm s^-1 on average at all moorings. Bottom currents (6 m above bottom) were eastward at ~5 cm s^-1 northwest of Hanna Shoal and northeast of the shoal there was a weak westward flow, ~1 cm s^-1. The measurements suggest zonal exchange with cold, fresh surface waters and ice transported westward and cold, dense bottom waters transported eastward. On the northeast side of Hanna Shoal, this exchange results in strong, year-round stratification, with the pycnocline at ~25m depth. The persistent stratification and sea ice affects the vertical structure of the circulation.