Analysis of the Seasonal and Interannual Variability of the Sea Surface Temperature Field in the Adriatic Sea from AVHRR data (1984 - 1992)

Seasonal and interannual variability of the sea surface temperature field in the Adriatic Sea is analyzed from the low-resolution advanced very high resolution radiometer data. The spatial resolution of 18 km allowed analysis of only basin and subbasin scale features. Average monthly and seasonal sea surface temperature fields for the entire studied period (1984-1992) are discussed. The analysis shows the absence of any permanent sea surface thermal features in the Adriatic Sea. The south Adriatic sea surface temperature minimum presumably associated to the cyclonic gyre, previously considered as one of the permanent features, appears to be recurrent, being prominent only in late autumn and early winter, i.e., in the preconditioning and a deepwater formation phases. The major Ionian water inflow is documented in autumn while the thermal signature of the western surface outflow of Adriatic water appears most prominent in winter. The variability of the basin-wide thermal pattern in the Adriatic reveals four distinct seasons, which is different from both the eastern and western Mediterranean, where only two major patterns are recognized. A prominent interannual signal occurs in a northward extension of the warm water plume along the eastern coast, which in some years reaches the northernmost corner of the Adriatic, while in other situations it remains trapped in the south Adriatic cyclonic gyre. The surface thermal signature of the south Adriatic gyre also varies on an interannual timescale, and it was weak or completely absent during the period 1984-1986 while it was rather prominent in the period 1987-1992. A constant trend of sea surface temperature decrease in the center of the south Adriatic gyre and in the northernmost corner of the Adriatic was evidenced over the studied period.