Modelling of Oceans Circulation

Abstract

The ocean covers 70% of the earth surface and it contains 97% of the earth water. It has a considerable “buffer” role in the climate system due to its large heat capacity (2.5 m of ocean water has the same heat capacity than the total atmospheric column above it) and its weight (the density of ocean water is 1.02 · 10³ kg m ^-3 as the air density is 1.2 kg m ^-3). The sea water has a temperature range within -1.90 to 32 ° C for a salinity of open sea varying from 33 to 37‰ but 75% of the oceans volume is filled with water in a very narrow range of temperature (between 0 and 4 ° C) and of salinity (between 34.4 and 34.7varying from 33 to 37‰ but 75%). In enclosed or semi-enclosed seas, much more variability can be found for temperature and salinity values. The vertical profile of temperature is nearly homogeneous in high latitudes and the constrast between surface temperature and deep temperature increases equatorward. In the equatorial band, a strong and sharp thermocline separates the warm reservoir from the cold deep waters. As we move polewards, the thermocline thickens and deepens. These properties are common to the three oceans in winter conditions. The water mass distribution and the ocean circulation are closely linked together and the water mass properties are determined through complex air-sea interactions. It is thus very important to understand and to model the air-sea interactions and how surface properties are transfered into the deep ocean. The ocean communicates with the atmosphere via exchanges in momentum, in water flux and heat flux.