Nonhydrostatic aspects of coastal upwelling meanders and filaments off eastern ocean boundaries

Abstract

Coastal upwelling meanders and filaments are common features off eastern ocean boundaries.Their growth is reinvestigated herein using a nonhydrostatic three-dimensional model and areduced-gravity model, with the objective of assessing contributions from two mechanisms thatemerge in the nonhydrostatic regime. The first mechanism is caused by the vertical projectionof the Coriolis force in the momentum equation. It is found that the vertical Coriolis forceoften acts as a restoring force against numerical damping off eastern ocean boundaries andthus enhances the growth of meanders and filaments. The second mechanism arises fromunstable ocean stratification when the cold upwelled water intrudes seaward over the warmlayer. The unstable stratification, albeit transient, further enhances the growth of meanders andfilaments. It is concluded that although nonhydrostatic effects do not change our understandingof how meanders and filaments grow, the realism can be enhanced using a nonhydrostaticmodel insofar as meanders and filaments off eastern ocean boundaries are concerned.