Influence of climatic changes on oceanographic properties of the Adriatic Sea

Abstract

        In order to explain possible influence of climatic changes on the oceanographic properties of the Adriatic Sea, available historic datasets (hydrographic, sea level and meteorological ones) are studied. Three important time scales are investigated separately: secular, interannual and sea­sonal. At a secular time scale, basic climatic oscillation was determined analysing long-term records of meteorological and sea level data for the Trieste station. Interannual variations of sea surface temperature and sea level along the eastern Adriatic coast as well as data series of temper­ature and salinity for the vertical profile in the open middle Adriatic were described using the cor­relation matrix based principal component analysis. The results were compared to the conditions in the atmosphere, leading to the conclusion that changes in atmospheric pressure account for a significant part of low frequency sea level changes. Additionally, thermohaline fluctuations in the surface layer were correlated with the atmospheric forcing, while the intermediate layer responded to the pressure gradient between the northern and southern Adriatic. At a seasonal scale, thermo­haline fluctuations (described in terms of the principal component scores) in comparison to the heat and water fluxes point to the fact that atmosphere strongly affects the seawater properties of the surface layer. In this layer, temperature and salinity vertical gradients are well related to the surface fluxes all the year round. In deeper layers this influence is observed only under vertically homogenous conditions. From heat and salt balances in this layer, it follows that two different sea­sons could be distinguished: a cold season with important vertical processes and a warm season with prevailing horizontal exchanges.