Atmospheric and Po River Discharge Anomalies in 2017: Impacts on Water Properties of the Adriatic Sea and North Ionian Sea

Abstract The Adriatic Sea’s heat and salt budget depends on three factors: atmospheric forcing, river runoff, and flux from the Ionian Sea. In 2017, an increase in salinity was observed in the Adriatic Sea. However, limited research has been conducted to precisely understand the internal factors (atmospheric forcing and river runoff) of the Adriatic contributing to this high salinity. In this study, we investigate the impact of atmospheric forcing and Po River discharge on the Adriatic Sea’s heat and salt budget, focusing on the years 2017 and 2018. Using an ocean model, we found that the Adriatic Sea experienced a loss of net atmospheric heat flux and a decrease in Po River discharge in 2017, leading to notable changes in its heat and salt budget compared to 2018. Specifically, the Adriatic Sea lost 20–30% more net heat flux in 2017 than in 2018. Substantial variations in temperature and salinity fluxes were observed, with a 9,000 ℃ m 3 /s increase in temperature flux and an 8,000 P.S.U m 3 /s rise in salinity flux in the southern Adriatic during 2018. Changes in surface circulation patterns indicated heightened gyre strength in the southern Adriatic and strengthened east–west currents in the Ionian Sea during the summer of 2018. The decrease in river discharge from the Po River resulted in an increase of 0.2–0.3 P.S.U in salinity in the Adriatic Sea, contributing to a density increase of 0.2–0.4 kg/m 3 . These findings underscore the sensitivity of the Adriatic Sea to atmospheric forcing and Po River discharge, which have implications for our understanding of global warming.