Structure of climatic variability of the Mediterranean Sea surface temperature. Part II. Principal modes of variability

The interdecadal and interannual variability of the Mediterranean Sea surface temperature (SST), presented by the first and second modes of empirical orthogonal functions (EOF), respectively, is studied using the 1951–2000 data. It is demonstrated that the spatial and temporal structure of the first EOF mode, reflecting interdecadal SST variations, is similar in all seasons, and, thus, is a manifestation of a global signal that is not subject to significant seasonal changes and whose origin is common for all seasons. On the contrary, the second EOF mode, reflecting the interannual variability of the Mediterranean Sea surface temperature and presented by a zonally oriented dipole, demonstrates its well pronounced seasonality. It is found that the character of temporal variability of this mode is specific for each season. The seasonality is also pronounced in significant variability of the mode contribution to the total SST variability. The above-noted seasonal differences are indicative of various mechanisms of formation of the interannual SST variability in the Mediterranean Sea.