An investigation of the link between lead-induced thermohaline convection and arctic eddies

Abstract

A recent laboratory study indicates that a turbulent buoyant line plume discharging into a rotating stratified fluid provides a natural mechanism for generating a series of anticyclonic geostrophic vortices [Bush and Woods 1999]. Here we examine the implications of these experimental results in the context of the thermohaline convection which develops when saline water is released as leads freeze over in the polar oceans. Using the experimental results in conjunction with a simple numerical model of plume dynamics in a non-uniformly stratified environment, we develop a model which characterizes the geometry of the eddies which would develop owing to lead-induced convection. The model predicts that, in the absence of strong currents, lead-induced thermohaline convection may generate anticyclonic geostrophic vortices of characteristic radius 2-10 km at the base of the mixed layer; however, this mechanism cannot account for the arctic eddies observed at substantial depths beneath the mixed layer, cyclonic, or strongly ageostrophic eddies.