Winter CO2 fluxes in a coastal sea: North Adriatic-Gulf of Trieste

The Northern Adriatic is a shallow, semi-enclosed sub-basin surrounded by an industrialized area in the northernmost part of the Mediterranean. The basin can be affected by intense air sea fluxes (gas, heat and water) and significant ecosystem changes. Dense water may form during winter (Northern Adriatic Dense Water, density anomalies > 29.2 kg m?³) and spread to the South along the Italian coast. Consequently the North Adriatic Sea seems interesting to the ICOS targets and the site in Gulf of Trieste, equipped for marine CO? measurements, was included in the ICOS Italy network. In the last few decades, ocean acidification of locally formed dense waters was estimated by non continuous data, spanning 25 years (Luchetta et al. 2010), thus indicating the area is prone to absorb CO? during winter. Then (2008), time series of the main physical and biogeochemical parameters (T, S, DO, nutrients, pH, TA, TOC) started being collected once per month by the fixed station (PALOMA) in the centre of the Gulf of Trieste. Gathered data indicate that dissolved CO? is driven by the sea temperature, the Gulf of Trieste is under saturated (290<surface pCO?<350 ?atm), in particular during winter, and can acts as a sink with calculated CO? fluxes of about 11.6 mmol m?² d?¹ during Bora wind events (Cantoni et al. 2012) or even higher than 60 mmol m?² d?¹ during extreme events, as in winter 2012 (Cantoni et al. 2015). The former estimates match those reported by other groups collecting data on local scale (Turk et al. 2010). During 2013 the elastic beacon PALOMA was implemented with continuous dissolved pCO? measurements (3 m depth) and air pCO? (9 m above the sea level). Here the calculated fluxes (from the continuous measurements) referring to the 2012-2013 and 2013-2014 winter season are presented.