The adjustment of a shelfbreak jet to cross-shelf topography

Abstract

A rigid-lid, finite-difference numerical model is used to study the adjustment of inviscid, along-shelf, barotropic shelfbreak jets to cross-shelf, channel topography. The channel is embedded in the shelf topography perpendicularly to the shelfbreak, the shelfbreak jet flows with the direction of propagation of long-wavelength, topographic Rossby waves, and the coast is sufficiently distant so as not to affect the flow. Three models are used that vary the strength of the channel topography S= f ΔhD/Uh , where f is the Coriolis parameter, Δ h is the difference between the shelf depth and the channel depth, D is the width of the slope into the channel, U is the maximum speed of the jet at the inflow, and h is the depth of the shelf. Estimation of the path of the jet from the inflow parameters and the geometry of the channel is possible in some cases. Generally, for large S the flow follows the topography of the channel and for small S the flow crosses the channel. The motivation for this study is the episodic flow of Scotian Shelf water from the Scotian Shelf across the Northeast Channel to Georges Bank. The steady, inviscid, non-linear, barotropic dynamics studied here do not allow such a flow for a channel of similar dimensions to the Northeast Channel and for flow speeds within the oceanographic range. Other factors such as stratification, wind stress and time variability need to be introduced to account for this phenomenon.