Variability of the Cyprus warm core Eddy during the CYCLOPS project

摘要

The circulation of the southeastern Levantine Basin (Eastern Mediterranean) as determined from several oceanographic cruises carried out in April, May, and August 2001 and in March, May, and August 2002 was investigated within the framework of the CYCLOPS experiment. The May cruises were part of CYCLOPS while the others, which provide supporting data, were part of the ongoing CYBO project. The May 2002 data provided the location of the eddy and physical description of the circulation, which were crucial for the in situ phosphate/SF_6 addition experiment of CYCLOPS. The major flow features observed in the region south of Cyprus displayed strong variability within the period of the observations. Throughout the entire study period, the warm core, anticyclonic eddy, known as the Cyprus eddy, was a dominant component of the circulation. During the 18 months covered by the cruises, the eddy drifted slowly to the southwest. At the end of the CYCLOPS cruises, the center of this persistent, recurrent eddy was found approximately 100-150 km west of its previously observed location since the 1980s. The mid-Mediterranean jet (MMJ), associated with the rim of this eddy, followed a complex path south of Cyprus depending upon the eddy's shape and location. During most of the study period the MMJ surface currents near the northern periphery of the rim of the eddy were as high as 35-45 cm/s. In May 2002, during the in situ experiment, the near surface seasonal thermocline inhibited downward mixing of the added tracers while the strong horizontal current around the rim of the clearly defined eddy core limited the lateral spreading and dilution of the patch. Finally, the westward shift of the Cyprus eddy allowed space for the generation of a secondary anticyclonic eddy in the eastern part of the domain. The co-existence of the two anticyclonic eddies during 2002 along with the development of a third anticyclonic eddy closer to the coast of Egypt provides strong evidence for the re-establishment of the previously observed, multi-pole, sub-basin scale Shikmona gyre.