Transports and budgets of anthropogenic CO2 in the Eastern North Atlantic Subtropical Gyre during 2009

Abstract

During ORCA 1009 project in the eastern boundary of the North Atlantic subtropical gyre, pH, total alkalinity and total inorganic carbon were measured along the three section in the area between 29-37ºN and 9-24ºW. The anthropogenic carbon content, Cant, was computed applying the back-calculation techniques TrOCA 2007 and !"# $ methods. Slightly higher concentrations of Cant in surface and intermediate waters was obtained by the TrOCA 2007. In contrast, lower concentrations were estimated in depth waters. The differences between the methods are mainly related to the different parameterizations of the pre-industrial and preformed properties and from the disequilibrium parameterizations. The large inflow of Cant to the region is through the western section (712 kmol -1) caused by the Azores Current. The Azores Current mostly feed the Canary Current at surface waters, the reasons behind the relatively high output of Cant estimated for this current (- 440 kmol -1). In the northern transect, we observed a southward flow of - 50 kmol s-1 influenced by the Portugal Current and finally, the MOW (in the eastern section) as goes out of the Mediterranean, deeps at intermediate waters, and intensifies the Azores Countercurrent (eastward) by – 70 kmol s-1.