Seasonal sea level variations in the Adriatic

Seasonal changes of the Adriatic Sea level, obtained by analyses of monthly sea level data measured at the Split tide gauge station in 1958-2001, are reported. The data were correlated by multivariant analysis to (1) local meteorological data on air temperature, air pressure, and precipitation, collected at the Split station and data on winds obtained from ECMWF ERA40 Reanalysis fields and (2) forcing mechanisms series (air pressure, surface heat flux, surface water flux, river runoff, winds). Surface flux data were available for only the northern Adriatic and the Po River represented all river runoff. The surface flux explains 68% of the variance in sea level while changes in local meteorological parameters explained 53%. Most of the variance was induced by changes in air pressure (32%) and heat flux (28%), while other factors did not contribute much. By determining annual (Sa) and semi-annual (Ssa) cycles, the explained variance increased to 88% for Sa tide and 95% for Ssa tide; changes were caused mostly by changes in air pressure (about 50% of the variance). Changes in the Sa heat flux cycle did not affect changes in the Sa tide but did affect Ssa tide (about 26% of the variance), presumably due to nonlinear effects driven by winds.