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 with the Variational Inverse Method using the DIVA software. Climatological maps were 5 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 variability associated with the climatological structures. In order to verify the temporal stability of the climatology, long-term variability has been investigated in the Mid Adriatic and 10 the South Adriatic Pits, regarded as the most suitable records of possible long-term changes. Compared with previous climatologies, this study reveals a surface temperature rise (up to 2 C), a clear deep dissolved oxygen minimum in the South Adriatic Gyre and a bottom summer oxygen minimum in the North Adriatic. Below 100m all properties profoundly differ between the Middle and the South Adriatic. The South Adriatic 15 Pit clearly shows the remote effects of the Eastern Mediterranean Transient, while no effect is observed in Middle Adriatic Pits. The deepest part of the South Adriatic seems now 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), even though a long-term temperature trend could not be statistically demonstrated. Con20 versely, 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−1 after the 1970s).