Temperature and salinity trends in the upper waters of the Mediterranean Sea as determined from the MEDATLAS dataset

The historical database (Published by IFREMER/DITI/IDT on behalf of the MEDATLAS consortium under contract MAS2-CT93-0074, 1997) is analysed on a seasonal basis for trends in the surface and intermediate water masses of the Mediterranean Sea. Significant trends are found in both the East and West Mediterranean but often to differing degrees. The upper waters of the entire Eastern Mediterranean Basin have been undergoing a sustained period of cooling throughout all seasons since about 1950. Salinities have also been found to be increasing over the same period with the strongest trends often being found at the shallowest horizontal levels examined. The Western Mediterranean Basin exhibits the same salinification throughout the upper waters as seen in the Eastern Mediterranean but the temperature trends are more varied and a basin wide cooling is not evident. The origin of these trends is most likely related to changes in the large-scale meteorological forcing of the Mediterranean region. The magnitude of changes to Levantine Intermediate Water (LIW) are in fact smaller than previously suggested thus indicating that the transfer of properties from the East to West Mediterranean via the LIW is not the major contributor to changes in the deep water characteristics of the Western Mediterranean.