Structure and evolution of warm core Eddies in the eastern M•diterranean levantine basin

Two recent cruises of the R/V Shikmona provided detailed coverage of a large portion of the Levantine Basin of the eastern Mediterranean. The first cruise was conducted in October 1985, corresponding to late summer, and the second was in March 1986, corresponding to the following winter. An objective analysis of the combined conductivity temperature-depth and expendable bathythermograph data from these cruises reveals a variety of warm core and cold core mesoscale eddies during both seasons. Some of these features are unique to each cruise while others appear to retain their identities from summer to winter. Of the latter, there are two intense anticyclonic eddies. One of these appears to have formed off the coast of Egypt as a meander of the North African current. The other is a rather persistent quasi-stationary feature to the southeast of Cyprus which has been seen near this location for over 3 years. Lack of adequate satellite images for the period and region covered led us to use water mass properties to identify and track the development of these two eddies. Below the layer of seasonal influence it was found that each eddy had a unique signature in its TS diagram which changed very little over the 6 months covered by the two cruises and the period between them. The water mass properties also provide additional evidence as to the possible formation regions for these two eddies. the discoveryo f an energeticm esoscalec irculation field in the Levantine Basin. This was first established by Robinson et al. [1987] using a subset of the data collected by the Israeli R/V Shikmona during the first coordinated POEM cruise in October 1985. Subsequently, a similar conclusion was drawn by Hecht et al. [1988], based on the analysis of data from 17 cruises of the R/V Shikmona in the region south of Cyprus between February 1979 and December 1984. Both of these studies have conclusively demonstrated the existence of a wealth of mesoscale features including large and small eddies, fronts, and jets with speeds as high as 40 cm/s. This is in contrast to the traditional picture of the circulation which was depicted as a smooth basin-wide cyclonic gyre with several superimposed weak subbasin scale gyres and speeds of 20 cm/s or less [e.g., Ovchinnikov, 1966]. In this study we will trace the evolution of two anticylonic, warm core eddies which retain their respective identities over a period of at least 6 months. Our results are based on data collected by the R/V Shikmona during the first two POEM cruises. The region of interest is the area enclosed in the large rectangle in Figure 1.