The Relationship of Pycnobathic Currents and Baroclinic Torques

Abstract

Recent work has shown the importance of baroclinicity?bathymetry interactions in diagnostic calculations of the current field from hydrographic data. In particular, pycnobathic currents can be generated by the presence of an alongshore-bottom density gradient in a shelf-slope domain. We investigate the nature of the pycnobathic term, which is proportional to the product of the alongshore-bottom density gradient and the bottom slope (for a sea floor that varies in depth in the offshore direction only). Previous work involves formulations that calculate the vorticity of the alongshore-bottom velocity. It is shown that this vorticity is proportional to the magnitude of the relative vorticity vector perpendicular to the bottom. Therefore the offshore component of the baroclinic torque is introduced into the dynamics and accounts for the presence of the pycnobathic term.