Satellite and hydrographic observations of eddy‐induced shelf‐slope exchange in the northwestern Gulf of Alaska

Abstract

Satellite and hydrographic observations of oceanographic conditions in the northwestern Gulf of Alaska indicate that anticyclonic eddies propagating adjacent to the continental shelf alter the structure of the shelf break front and, in doing so, influence the shelf‐slope exchange of biota and water mass properties. Eddies typically form in the northern Gulf of Alaska during fall and winter and propagate southwestward within an ∼200 km wide corridor along and above the continental slope. Eddy activity within this corridor diminishes in the downstream direction. The trajectories of faster propagating (>4 km/day) eddies tend to lie closer to the shelf break than do the trajectories of slower propagating (∼1.5 km/day) eddies. The interaction between azimuthal eddy currents and the shelf break frontal jet (1) establishes an upwelling zone, associated with the leading flank of the eddy, that strengthens cross‐slope gradients, (2) weakens cross‐slope gradients and promotes shelf‐slope exchange where the eddy is adjacent to the shelf, and (3) reestablishes a weak upwelling zone associated with the trailing flank of the eddy.