Evolution of a Mediterranean Salt Lens: Scalar Properties

Abstract

The evolution of a Mediterranean salt lens (Meddy) over a two year period is examined. Several nondimensional numbers can be used to describe the overall decay in the structure of the Moddy. Two Rossby numbers, one using the central relative vorticity and another using the radius and velocity of the azimuthal velocity maximum, did not change over the two year period. However, the Burger number N2H2/(f2L2) increased as the Meddy decayed. Another Burger number, the ratio of total kinetic energy to total available potential energy, decreased from 1.1 to 0.6 over a one year period. The rates at which the Meddy lost salt and heat are consistent with estimates of horizontal fluxes by intrusions. A horizontal diffusivity of O(5 m2 s−1) is needed if this flux by intrusions is parameterized by an eddy coefficient. Simple models of the evolution of an isolated eddy by horizontal and vertical mixing of mass and momentum are examined. These simple attempts to explain the evolution of the Meddy suggest more complicated models are necessary to reproduce its decay.