Tracer Transport During the Geostrophic Adjustment in the Equatorial Ocean

Abstract

Transport and mixing processes during the geostrophic adjustment of a localized perturbation in the equatorial ocean are investigated numerically in the reduced gravity model. A finite volume scheme is designed which computes the advection of a (complex) tracer field together with the evolution of the dynamical variables. This method permits the study of transport processes.The model supports the propagation of a finite amplitude Rossby waves with a closed recirculation region. The mass trapping occurs for solitary waves with relative amplitude greater than 0.3. Numerical simulations show that trapping can happen during the propagation of a small amplitude soliton on a sloping thermocline.Transport during the process of geostrophic adjustment of localized perturbation is studied. An initial height or zonal velocity anomaly is split up into a fast zero group velocity gravity wave and a slow component which consists in a Kelvin wave and a Rossby wave. While Kelvin and gravity waves modify the tracer field through the Stokes drift only, the Rossby wave is transporting mass away from the initial perturbation westward.KeywordsGeostrophic adjustmentequatorial dynamicstracer transport