A 1 year sea surface heat budget in the northeastern Atlantic basin during the POMME experiment: 2. Flux optimization

Abstract

Gridded air-sea fluxes were computed during a 1 year period by applying a synthesis approach (Caniaux et al., 2005) as part of the Programme Océan Multidisciplinaire Méso Echelle (POMME) (September 2000-October 2001 in the northeast Atlantic 21°-15°W, 38°-45°N). In the present paper we address the question of adjusting the precipitation and turbulent surface fluxes so that the corresponding heat, salt, and momentum budgets are in agreement with the evolution of the thermal and salt contents deduced from the data collected during the experiment. The proposed method is based on the one-dimensional modeling of the whole POMME area by solving specific temperature and salinity equations (including advective terms) and on the optimization of adjustable coefficients with a genetic algorithm. Adjusted fluxes allow us to simulate the average sea swface temperature and salinity with errors less than 0.02°C and 0.02 psu, respectively, over 1 year. The corresponding new surface heat budget indicates that the adjusted annual net heat (+17 W m-2) is Weaker than previously calculated (+331 W m-2) but remains positive, meaning a heat gain for the ocean. The adjusted annual salt budget reveals a net evaporation of 0.75 mm d-1 for the POMME region. In contrast with climatology we find that the zone is located southward of the null buoyancy flux area during September 2000-September 2001. Copyright 2005 by the American Geophysical Union.