Title

The role of small scale cells in the Mediterranean convection process

Date of Award

1993

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Kevin D. Leaman, Committee Chair

Abstract

Vertical velocity time series, obtained from an ADCP mooring deployed in the Gulf of Lion in the Northwest Mediterranean, indicated that the deep convection, known to occur in that region, was organized into small scale (O(1 km)) cells embedded in a larger scale (O(50 km)) homogeneous 'patch'. A linear analytic model, used successfully to describe convective cells in rotating laboratory tank experiments, accurately predicted the length scales of the cells. Rotation of the horizontal currents, either cyclonic or anticyclonic, derived from current meters at various depths, seemed to accompany the bursts of vertical velocity in some cases, but no statistical correlation was found. Velocities from current meters showed that during the period of strong surface forcing, a front of increased kinetic energy propagated downward, finally reaching the bottom. An analytic expression for the depth of penetration of this front, as a function of time and surface buoyancy flux, was derived using a simple one dimensional model of the density profile. Stratification in the central part of the 'patch', after the kinetic energy front reached the bottom, was neutral. These results indicate that the Mediterranean cells are more complicated structures than the laboratory tank cells. The primary role of the cells is to provide the turbulence necessary to efficiently mix the water column and remove the existing weak but stable stratification. Another role of the cells might then be to provide a mechanism for the advection of surface water to the bottom.

Keywords

Physical Oceanography

Link to Full Text

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