Process Studies of the Complex Mesoscale Circulation Observed in the Western Mediterranean Sea

Satellite observations of the Mediterranean Sea reveal complex circulation patterns which are time-dependent. This is in contrast to the simple idealized flow patterns presented in historical studies based on limited in situ observations. These pre-satellite studies were based on collections of data which were not synoptic in time nor space. A series of process studies using a hierarchy of numerical ocean models has been undertaken in an attempt to elucidate the dynamics controlling the observed circulation. The numerical models used are variations of a multilayered primitive equations model. The simplest version is a one-active layer, reduced gravity model forced by winds, inflowoutflow mass flux andor density variations. The results from this version yield flow patterns which are qualitatively similar to the historical representations, but do not help to understand the time-dependent mesoscale variability observed in the remotely-sensed data. Additional complexities such as multiple layers allow for baroclinic instabilities. Bottom topography, realistic non-climatic wind stress, etc. add to the realism of the numerical simulations. In most cases a combination of forcing mechanisms are required to produce a simulation of the observed circulation patterns. mm