A novel description of the phenomenology of the Eastern Mediterranean is presented based upon a comprehensive pooled hydrographic data base collected during 1985–1987 and analyzed by cooperating scientists from several institutions and nations (the POEM project). Related dynamical process and modeling studies are also overviewed. The circulation and its variabilities consist of three predominant and interacting scales: basin scale, subbasin scale, and mesoscale. Highly resolved and unbiased maps of the basin wide circulation in the thermocline layer are presented which provide a new depiction of the main thermocline general circulation, composed of subbasin scale gyres interconnected by intense jets and meandering currents. Semipermanent features exist but important subbasin scale variabilities also occur on many time scales. Mesoscale variabilities modulate the subbasin scale and small mesoscale eddies populate the open sea, especially the south-eastern Levantine basin. Clear evidence indicates Levantine Intermediate Water (LIW) to be present over most of the Levantine Basin, implying that formation of LIW is not localized but rather is ubiquitous. The Ionian and Levantine basins are confirmed to form one deep thermohaline cell with deep water of Adriatic origin and to have a turnover time of one and a quarter centuries. Prognostic, inverse, box and data assimilative modeling results are presented based on both climatological and POEM data. The subbasin scale elements of the general circulation are stable and robust to the dynamical adjustment process. These findings bear importantly on a broad range of problems in ocean science and marine technology that depend upon knowledge of the general circulation and water mass structure, including biogeochemical fluxes, regional climate, coastal interactions, pollution and environmental management. Of global ocean scientific significance are the fundamental processes of water mass formations, transformations and dispersion which occur in the basin.

The variability of the Levantine Basin circulation and hydrography is reviewed based on a collection of recent data sets. The major emphasis is placed on the complexity of the associated dynamics. The region is shown to be populated with synoptic and mesoscale dynamic features. In addition to the complexity arising due to the heterogeneity of water masses and the variability of the atmospheric and thermohaline forcing, the confines of the relatively small basin causes the sub-basin-scale gyres to be in close contact with each other, resulting in interacting, basin-wide turbulent features. The bifurcation of the mid-Levantine jet near Cyprus is variable on interannual time-scales, the amount of bifurcation of the fluxes being dependent on the evolution of the circulation in the multi-connected domain and the relative intensities of the sub-basin-scale gyres. During the 3-year observation programme, qualitative changes are identified in the general circulation. The flow encircling Cyprus is partially blocked in the first phase of the experiments. Later, the two basins on the north and east sides of Cyprus are flushed with new water masses carried in the cores of incident eddies, and a new pattern of basin-wide circulation is established, with a major part of the mid-basin jet flowing coherently along the mainland coasts and cyclonically around Cyprus. As a consequence, the general circulation of the Levantine Basin appears considerably different and more complex than the traditional descriptions of it.