Bathymetric Influences of the Emperor Seamounts upon the North Pacific Subarctic Gyre : Boundary Current along the Eastern Side of the Emperor Seamounts

Abstract

To make clear bathymetric influences of the Emperor Seamounts upon the North Pacific subarctic gyre, numerical experiments were performed using two-layer model with an idealized wind and ridge. Seasonally varying interior Sverdrup transport to the east of the ridge partly returns along the eastern side of the ridge as a western boundary current. A ratio of the boundary transport to the interior transport depends on a ridge height (H_R) and stratification (N). For smaller H_R (H_R/H_0 < 0.3 where H_0 is background water depth), the ratio increases with H_R, but it changes little with N. For larger H_R (HR_/H_0 > 0.3), the ratio decreases with N but is independent of H_R, Spatial distribution of geostrophic contours is a key to understand the dependence of the ratio on H_R and N. For smaller H_R, the ratio almost coinsides with a ratio of the number of closing geostrophic contours to one of all geostrophic contours. For larger H_R at which all geotstrophic contours in the eastern region cannot cross over the ridge, bottom pressure torque decreases with N to allow more transport across the ridge