Qualified temperature, salinity and dissolved oxygen climatologies in a changing Adriatic Sea

An updated climatology, based on a comprehensive dataset (1911–2009) of temperature,salinity and dissolved oxygen, has been produced for the whole Adriatic Sea withthe Variational Inverse Method using the DIVA software. Climatological maps were5 produced at 26 levels and validated with Ordinary Cross Validation and with real vs.synthetic Temperature–Salinity diagram intercomparison. The concept of Climatology–Observation Misfit (COM) has been introduced as an estimate of the physical variabilityassociated with the climatological structures. In order to verify the temporal stabilityof the climatology, long-term variability has been investigated in the Mid Adriatic and10 the South Adriatic Pits, regarded as the most suitable records of possible long-termchanges. Compared with previous climatologies, this study reveals a surface temperaturerise (up to 2 C), a clear deep dissolved oxygen minimum in the South Adriatic Gyreand a bottom summer oxygen minimum in the North Adriatic. Below 100m all propertiesprofoundly differ between the Middle and the South Adriatic. The South Adriatic15 Pit clearly shows the remote effects of the Eastern Mediterranean Transient, while noeffect is observed in Middle Adriatic Pits. The deepest part of the South Adriatic seemsnow to be significantly saltier (+0.18 since the period 1911–1914, with an increase of+0.018 decade−1 since the late 1940s) and warmer (+0.54 C since 1911–1914), eventhough a long-term temperature trend could not be statistically demonstrated. Con20versely, the Middle Adriatic Pits present a long-term increase in apparent oxygen utilisation(+0.77mLL−1 since 1911–1914, with a constant increase of +0.2mLL−1 decade−1after the 1970s).