Energy conversion in the Cape Verde Frontal Zone

Abstract

Mechanical energy terms are calculated from moored current meter data in the Cape Verde Frontal Zone (about 20°N, 25°W) and compared with those derived from a mesoscale model of this frontal region. The model is of the Bleck and Boudra [1981] type with isopycnal coordinates. An initially zonal jet, representing the Canary Current, is allowed to develop under the influence of baroclinic and barotropic instability processes. We find reasonable agreement in magnitudes, somewhat smaller in the model, and similar distributions in the vertical. This leads to the conclusion that the energy transfer terms from the model can be expected to be sufficiently close to reality. Determination of the transfer terms confirms that the energy transfer in the zone is dominated by baroclinic instability processes while barotropic instability is of minor importance. Average baroclinic instability energy transfer terms reach values of 2–3 μW m−3 in the pycnocline. Peak layer mean values are of the order 10 μW m−3. It is shown that the spatial distribution of active transfer regions is closely related to the structure of the transient eddy field in the frontal zone and that strong instability processes are restricted to the pycnocline.