Effect of topography and mixing parameterization upon the circulation in cold water domes

Abstract

The influence of bottom topography and the parameterization of subgrid‐scale mixing upon the steady state circulation in a cold water bottom dome was examined using a three‐dimensional prognostic model in cross‐sectional form. Initially, the circulation due to a specified bottom dome and surface frontal system associated with observed domes are considered in isolation. Calculations revealed a cyclonic (anticlockwise) circulation in the surface layer, with an anticyclonic (clockwise) circulation in the near‐bed layer, associated with an isolated bottom dome. In the case of the surface frontal system, calculations showed surface and near‐bed circulations in the opposite directions to those found for a bottom dome. For the surface frontal case, the maximum current occurs at the sea surface, with a weak current at the bed. Calculations showed that topography had little effect. In subsequent calculations, surface front and bottom dome in combination were examined. In this case their form was not specified but was generated by solar heating, and calculations showed that topography had an important role. The opposing nature of the circulations associated with the surface front and bottom dome leads to a dominant near‐surface cyclonic current circulation at the edge of the dome, with weaker secondary circulations beyond this. Cross‐frontal circulation cells were generated in the vertical. The strength and exact form of these circulations depended upon the topography and parameterization of mixing.