Two Configurations of the Western Arctic Shelfbreak Current in Summer

Data from a closely-spaced array of ocean moorings situated across the Beaufort Sea shelfbreak at 152°W are used to study the Western Arctic shelfbreak current, with emphasis on its configuration during the summer season. Based on the two-year mean---from August 2002 to August 2004---between 10% and 20% of the volume, freshwater, and heat flowing through Bering Strait are transported eastward by the current.  There are two dynamically distinct configurations of the current that advect Pacific Summer Water in the absence of wind, each lasting approximately 1 month. The first configuration is a surface-intensified shelfbreak jet transporting warm and buoyant Alaskan Coastal Water in late summer. This is the eastward continuation of the Alaskan Coastal Current. It is both baroclinically and barotropically unstable and hence capable of forming the surface-intensified warm-core eddies observed in the southern Beaufort Sea.  The second configuration, present during early summer, is a bottom intensified shelfbreak current advecting weakly stratified Chukchi Summer Water. It is baroclinically unstable and likely forms the mid-depth warm-core eddies present in the interior basin. These mesoscale instabilities extract energy from the mean flow at such a high rate that both configurations of the current should spin down rapidly and not penetrate far into the Canadian Beaufort Sea. Different summertime wind regimes may also influence the fate of the shelfbreak jet. This is examined using additional oceanic timeseries data and atmospheric re-analysis fields.