NEAR-SURFACE MEAN CIRCULATION AND KINETIC-ENERGY IN THE CENTRAL NORTH-ATLANTIC FROM DRIFTER DATA

An analysis of a large drifting buoy data set is presented. The object ive is to obtain a self-contained description of the properties of the near-surface circulation (drogue depth 100 m) in the central North At lantic Ocean, independent of hydrographic data. A necessary preanalysi s step was the removal of all data from undrogued buoys from the data set. The physical parameters of the circulation were deduced by averag ing the remaining data in 2 degrees x 3 degrees boxes. The minimum amo unt of data which is necessary to get statistically stable results was determined by an empirical quality criterion. All important mean curr ents in the investigation area are reproduced by the near-surface mean velocity field. A separation of the mean velocity field into a nondiv ergent acid an irrational part shows that the flow field is almost non divergent. The distribution of eddy kinetic energy is concentrated alo ng the mean currents and provides the largest part of the total kineti c energy, but there are regional variations. Energy from inertial move ments dominates the high-frequency part of the kinetic energy. Its dis tribution is very patchy. The analysis of the Reynolds stress terms sh ows an energy transfer from the eddy field to the mean circulation in the vicinity of the North Atlantic Current.