BASIN-SCALE OCEAN CIRCULATION FROM COMBINED ALTIMETRIC, TOMOGRAPHIC AND MODEL DATA

The ocean stores and transports vast quantities of heat, fresh water, carbon and other materials, and its circulation plays an important rol e in determining both the Earth's climate and fundamental processes in the biosphere, Understanding the development of climate and important biological cycles therefore requires detailed knowledge of ocean circ ulation and its transport properties, This cannot be achieved solely t hrough modelling, but must involve accurate observations of the spatio -temporal evolution of the global oceanic flow field. Estimates of oce anic flow are currently made on the basis of space-borne measurements of the sea surface, and monitoring of the ocean interior. Satellite al timetry and acoustic tomography are complementary for this purpose(1), as the former provides detailed horizontal coverage of the surface, a nd the latter the requisite vertical sampling of the interior. High-qu ality acoustic-tomographic(2) and altimetric(3) data are now available to test the combined power of these technologies for estimating ocean ic flows. Here we demonstrate that, with the aid of state-of-the-art n umerical models, it is possible to recover from these data a detailed spatio-temporal record of flow over basin-scale volumes of fluid. Our present results are restricted to the Mediterranean Sea, but the metho d described here provides a powerful tool for studying oceanic circula tion worldwide.