Offshore transport of the Alaska Coastal Current water induced by a cyclonic wind field

Abstract

[1] The Alaska Coastal Current (ACC) is driven by multiple sources of coastal freshwater discharge and propagates alongshore over hundreds of kilometers. The ACC is also subject to downwelling-favorable winds associated with cyclonic wind systems. Spatially-uniform, downwelling winds trap the buoyant ACC waters nearshore. However, we demonstrate with numerical experiments that spatial wind variations, due either to a stationary or translating cyclone, can enhance the offshore transport of buoyant coastal waters in comparison to no-wind conditions. A stationary atmospheric cyclone induces a strong convergence in the coastal current at the upstream periphery of the cyclone. This convergence generates an offshore filament of buoyant water, which evolves into detached anticyclone. A transient atmospheric cyclone enhances the offshore spreading of freshwater by intensifying mesoscale variability of the coastal current. Thus, the spatial structure of the wind field represents a potentially important mechanism for cross-shelf freshwater transport.