The Siberian Coastal Current: A wind- and buoyancy-forced Arctic coastal current

We describe circulation and mixing in the Siberian Coastal Current (SCC) us ing fall shipboard measurements collected between 1992 and 1995 in the west ern Chukchi Sea. The SCC, forced by winds, Siberian river outflows, and ice melt, flows eastward from the East Siberian Sea. It is bounded offshore by a broad (similar to 60 km) front separating cold, dilute Siberian Coastal Water from warmer, saltier Bering Sea Water. The alongshore flow is incoher ent, because the current contains energetic eddies and squirts probably gen erated by frontal (baroclinic) instabilities. These enhance horizontal mixi ng and weaken the cross-shore density gradient along the SCC path. Eventual ly, the SCC converges with the northward flow from Bering Strait, whereupon it deflects offshore and mixes with that inflow. Deflection occurs where t he alongshore pressure gradient vanishes. That location varies on synoptic and seasonal timescales, because this gradient depends on the winds, buoyan cy fluxes, and the sea level difference between the Pacific and Arctic Ocea ns. Deflection usually occurs on the Chukchi shelf, but the SCC occasionall y flows southward through Bering Strait. Such events are short lived (1-10 days) and occur mainly in fall and winter under northerly winds. SCC transp ort is likely small (similar to 0.1 Sv), but its dilute waters could substa ntially freshen the Bering Strait inflow and affect the disposition of Paci fic waters in the Arctic Ocean. Arctic river outflows should preferentially form surface-advected fronts rather than bottom-advected fronts because ve rtical-mixing energy is low on arctic shelves. Surface-advected fronts are more susceptible to upwelling winds (and for the SCC, the pressure gradient between the Pacific and Arctic Oceans) than bottom-advected fronts. The SC C never developed in fall 1995 because of anomalously steady upwelling wind s. The western Chukchi shelf could have formed upper halocline source water in the winter of 1995-1996.