CIRCULATION AND FLUXES OF THE CENTRAL NORTH-ATLANTIC IN 1983/84 ESTIMATED BY INVERSE ANALYSIS OF TOPOGULF HYDROGRAPHIC DATA

It is well known that transports of mass and heat in the Central North Atlantic play a major role in maintaining the relatively mild climate of Western Europe. However, much controversy and uncertainty remain concerning the exchanges between the western and eastern basins. In an attempt to quantify and understand exchanges, we analyze the hydrographic data collected during the ''Topogulf' experiment which took place in summer 1983 and summer 1984. By means of inverse modelling, we investigate the general circulation and its associated transports. The role of the bathymetry is fundamental. For example, the meridional transport through the line of zero Ekman pumping which is equal to zero in wind driven gyre theory, becomes equal to 25.6 Sv when bathymetric effects are taken into account. A condition of small cross-isopycnal flow is imposed at mid-depth. It controls vertical velocities and improves the stability of the horizontal velocities with respect to small perturbations of input parameters. The mean error bars associated with integrated (0-1500 m) transport and temperature fluxes estimates are respectively 1.5 Sv and 0.07 PW. A major contribution of this study is that the deep flow is southward east of the Mid Atlantic Ridge and northward west of it.