Characteristics of an eddy over a continental shelf: Shelikof Strait, Alaska

Abstract

During May 1990, satellite‐tracked buoy, water property, and ichthyoplankton observations were collected over the Shelikof sea valley in the western Gulf of Alaska. These observations revealed the presence of an anticyclonic mesoscale eddy (radius 10–12 km). Characteristics of the eddy included a relatively warm, low‐salinity core and high concentrations of walleye pollock larvae. The eddy remained nearly stationary for several weeks before moving westward into shoaler waters. During translation, the eddy maintained its characteristics. Speeds from geopotential topography and direct measurements agreed. Current speeds generally increased with distance from the center of the eddy; maximum speeds (>30 cm s−1) existed near the perimeter. Analysis of water properties indicates little or no exchange of mass occurred with adjacent waters. The lack of dispersion permits us to estimate larval mortality (≤4.7% d−1) based only on biological factors. Eddy formation occurred through baroclinic instability upstream within Shelikof Strait proper.