An examination of the physical variability around the Pribilof Islands in 2004

The Pribilof Islands form a unique ecosystem. An anti-cyclonic oceanic flow exists around the islands. Nutrients are introduced into this circulation from two sources: (1) the flow along the 100-m isobath with intrusions of nutrient-rich water in Pribilof Canyon, and (2) the westward transport and vertical mixing of middle-shelf water, which contains nutrient-rich bottom water. Enhanced tidal mixing around the Pribilofs introduces this deeper, nutrient-rich water into the euphotic zone and thus supports prolonged production around the islands. Further, the middle-shelf water that is advected into the region causes the upper 50 m of the water column around the islands to freshen throughout the summer. This enhances the frontal structure and strengthens the baroclinic flow along the 100-m isobath. The strengthening of the frontal structure can moderate ecosystem productivity by limiting the intrusion of slope water rich in nutrients and oceanic copepods.