James Stephens

J. C. Stephens and R. W. Hallberg, 1999, Uncompleted Manuscript.

Abstract

We have conducted numerical simulations of the Mediterranean overflow in the vicinity of the Gulf of Cadiz, using a primitive equation isopycnal model in which the exchange between the Atlantic and the Mediterranean via the Strait of Gibraltar is explicitly resolved. Diapycnal mixing is represented using the recent Richardson number dependent mixing parameterization of Hallberg (99).

At 1/6 degree horizontal resolution and with 16 vertical layers, the model is able to represent the entrainment, descent in the water column, and water mass properties of the overflow current substantially better than in an identical case without the parameterization. Moreover, upon the inclusion of a quadratic drag law and a non-linear equation of state, the similarity of the solutions to observations is striking. At 1/3 degree horizontal resolution, many aspects of the Mediterranean water mass properties are also reproduced satisfactorily.

We observe plausible transports and properties of Mediterranean Water through the model Strait of Gibraltar, with little dependence on horizontal resolution. This suggests the possibility that future climate simulations using layered models attempt to explicitly resolve this exchange. In combination with a similar mixing scheme we expect to see fundamental improvements in the fidelity of deep and intermediate water masses.

This draft manuscript is available as a gzipped postscript file of uncompressed size 18 Mb here.