SURFACE CIRCULATION IN THE NORTHEAST ATLANTIC AS OBSERVED WITH DRIFTERS

ARGOS surface drifter data from the northern parts of the northeast At lantic over the years 1990-1993 have been analysed. The drifters had a drogue at a depth of 15 or 30 m. These data cover well over 10 drifte r years. The overall drift appeared to be towards the northeast. Analy sis by geographic area and by season revealed regional and temporal va riations of both the mean flow and the eddy statistics. In winter the drifter velocities had a tendency towards higher values, probably due to increased wind speeds. Highest eddy kinetic energy was found in the deep Iceland Basin, where an extension of the Sub-Arctic front was ob served, while the lowest eddy kinetic energy was observed over the sha llower Rockall Plateau. The strongest mean surface velocities were fou nd in the Iceland Basin,just west of the Rockall Plateau. They were co nnected with the Sub-Arctic front in this region. No evidence was foun d of westward transport of surface water across the Reykjanes Ridge to wards the Irminger Sea. Two drifters were observed to leave the area a cross the Iceland-Faroe Ridge, flowing eastwards over the northern Far oes slope, whereas two drifters left the area through the Faroe-Shetla nd Channel. The small banks in the area appeared to generate anti-cycl onic surface circulation on the scale of these banks. Over the larger Rockall Bank no preference for cyclonic circulation was found. The edd y kinetic energy was highest over the deep Iceland Basin where transie nt eddies were found with scalar velocities well over 20 cm s(-1), whi le the Rockall Plateau seems to be an ''eddy desert''. The dispersion due to the temporal variability of the Lagrangian surface velocity cou ld well be modelled with the simple Taylor's theory, with a good fit o f the data to the theoretical lines for timescales of 0.25-40 days. Co pyright (C) 1996 Elsevier Science Ltd.