New observations of CO2-induced acidification in the northern Adriatic Sea over the last quarter century

Current global trends will lead to large-scale changes in climate patterns, ocean circulation and stratification; increased atmospheric CO2 levels will cause acidification of the oceans, with significant impacts on marine biogeochemical cycles and calcareous organisms. In the Mediterranean area, the northern Adriatic Sea is one of the most suitable sites for studying the responses of marine pH to such occurrences because it is the northernmost basin affected by dense water formation during winter, and is also one of the most productive areas in the Mediterranean. The first comparison between two sets of data relating to the dense cold waters of the northern Adriatic, formed in the winters of 1982-1983 and 2007-2008, is presented here. pH values on the Nation Bureau Standard scale from the old dataset have been converted to the 'total hydrogen ion concentration scale' adopted for the new dataset, and are expressed as mu mol H+ . kg(sw)(-1). Results at 25 degrees C show acidification (-0.063 pH(T) units) and a decrease in carbonate ion concentration (-19.6 mu mol H+ . kg(sw)(-1)) in the dense water mass between 1983 and 2008, whereas total alkalinity, carbonate alkalinity, dissolved inorganic carbon and CO2 fugacity exhibit net increases of 74.4, 77.8 and 110.3 mu mol H+ . kg(sw)(-1), and 108.3 mu atm, respectively, over the same period.