Sea surface temperature and mixed layer depth changes due to cold-air outbreak in the Gulf of México

摘要

The impact of a cold-air outbreak (CAO) on the mixed layer in the Gulf of México (GoM), during the period 18-23 October 1999, is shown in this work. A numerical model, based on the thermal energy equation and the balance equation between the thermal and mechanical energies, is used for computing both, the sea surface temperature (SST) and the sea mixed layer depth (MLD) changes due to atmospheric forcing before and during the CAO. The importance of the contributions to the temperature tendency by thermal forcing at the surface, the vertical entrainment of cold water from the thermocline, the horizontal transport of thermal energy by ocean currents and by turbulent eddies in the mixed layer are analyzed, as well as the contributions to the entrainment velocity by deepening of the mixed layer and the Ekman's pumping velocity. During the passage of the CAO on the GoM the SST changes were markedly influenced by the increase in the surface wind speed. At the end of the period the experiments show that the vertical entrainment turned out to be the most determining process in the cooling of the mixed layer, even overhead of the latent and sensible heat fluxes and the horizontal transport by ocean currents and by turbulent eddies.