Interannual evolution of seasonal thermohaline properties in the Gulf of Trieste (northern Adriatic) 1991-2003

Temperature and salinity data, collected by conductivity-temperature-depth cruises over the Gulf of Trieste during 1991-2003, were analyzed using different methods. In the first analysis, the evolution within a year of monthly temperatures and salinities at the sea surface and at 10 m depth was examined. Temperature at the surface varies with an annual amplitude of 8.1 ± 0.4°C around 16.5°C, while at a depth of 10 m it varies with an amplitude of 7.0 ± 0.3°C around 15.5°C, the variation being delayed with respect to that at the surface for about 0.4 months. In the second analysis, the interannual variations of seasonal temperatures and salinities were examined. In this northernmost part of the Mediterranean Sea, summer temperatures at the surface between 1991 and 2003 were rising between 0.12 and 0.23°C/year with an error of 0.05°C /year. When the year 2003 with its extremely dry summer period was excluded from the analysis, the trend is reduced to 0.07-0.09°C/year (±0.06°C/year). Winter temperatures, however, demonstrate an increasing trend from near zero to 0.10°C/year ± 0.14°C /year when year 2003 was excluded from the analysis. Similar changes in trends have been observed for air temperatures. Summer temperatures at a depth of 10 m have a more reliable positive trend: 0.22-0.23°C/year (±10.08°C/year). Salinities obtained from the objective analysis show a most pronounced positive trend of 0.28-0.34 year-1 (±0.16 year-1). When 2003 is excluded from the analysis, this value decreased to 0.22-0.28 year-1 with an error of 0.09 year-1. Copyright 2006 by the American Geophysical Union.