A high-resolution simulation of the ocean during the POMME experiment: Simulation results and comparison with observations

Overview & Synopsis

A modeling study of physical processes occurring in an area of the northeast Atlantic (21.33°-15.33°W, 38.00°-45.00°N) that was extensively sampled during the Programme Océan Multidisciplinaire Méso Echelle (POMME) (October 2000-September 2001) is carried out. The model is a mesoscale version of the ocean general circulation model OPA developed at the Laboratoire d'Océanographie Dynamique et de Climatologie in Paris. It is used in a three-dimensional limited area domain with a high-resolution grid (approximately 5 km horizontal spacing, 69 vertical levels) and realistic boundary conditions (initial state, air-sea fluxes, open boundary fluxes, and bottom topography). The objectives of the study are to properly simulate the upper ocean dynamics, particularly mesoscale activity and mixed layer evolution, during a key period (restratification) of the POMME experiment (POMME 1 and POMME 2, from February to May 2001) and to compare model results with oceanographic observations collected during the experiment in order to establish confidence in the model. Some results provided by the high-resolution simulation, in particular features related to mixed layer depth and vertical velocities, are also presented. There is no pronounced north-south mixed layer depth gradient, but strong filament-shaped structures associated with stirring at the periphery of eddies are present. Mixed layer restratification is simulated. It is associated with submesoscale mixed layer depth structures and intense vertical velocity filaments in the upper ocean correlated with the relative vorticity gradient field.