Local and remote drivers of the observed thermohaline variability on the northern Adriatic shelf (Mediterranean Sea)

Abstract

In situ thermohaline variables measured monthly or bimonthly in the shallow northern Adriatic at prescribed stations between 1979 and 2017 were correlated with the local (river runoff, precipitation, net heat flux) and remote atmospheric (various hemispheric and regional indices) and oceanic (the Adriatic-Ionian Bimodal Oscillating System, BiOS) drivers acting on monthly to annual timescales. The highest correlation between the temperature and the local drivers was obtained in winter along the western part of the study area, while the rivers and precipitation mostly shaped the summer and December salinity values. The net heat fluxes and river discharges preceding the dense water formation (DWF) by 1–2 months and up to 3 months were found to be important for the February temperature and salinity variability, respectively. No significant correlations were found between the February thermohaline variables and the monthly BiOS index for the phase lags up to −11 months, while the correlation was the largest between the yearly averaged BiOS index and the yearly averaged salinity at phase lags of −2 to −4 years. The bottom yearly averaged salinity has also been highly correlated with the Mediterranean Oscillation index at phase lags of −1 and −3 years, while the yearly averaged surface temperature was influenced by the East Atlantic and East Atlantic/West Russia patterns. Acting independently on different timescales, both the local and remote processes were found to drive the thermohaline variability in the northern Adriatic, thus providing an option for a forecast of the DWF and the thermohaline circulation in the Adriatic-Ionian basin.