Inertial Western Boundary Current on a Bottom Slope: Effects of Horizontal Viscosity and Inshore Conditions

Abstract

The author investigates how the path of the subtropical inertial western boundary current on a bottom slope is affected by viscosity, coastal boundary condition, and width of the continental shelf. Steady flow patterns of a weakly viscous homogeneous model are considered. When viscosity is weak and a no-slip boundary condition is given, the boundary current crosses the shelf/slope offshore controlled by the ageostrophic term in the momentum balance so that the velocity change along the path is small. The path is similar to the inertial boundary layer model with a velocity front. It is independent of the viscous coefficient as long as it is weak. When a free-slip condition is given, the boundary current follows the coastline without being detached from the coastline. The width of the shelf changes the nature of the boundary current considerably. For both boundary conditions, two separate jets are made. The offshore jet, which carries most transport of the gyre, tends to follow a contour of f/H. A critical shelf width divides two classifications for each boundary condition. It has a different value for each condition.