Rising surface ocean dissolved inorganic carbon at the Hawaii Ocean Time-series site

Surface ocean dissolved inorganic carbon (DIC) and titration alkalinity have been measured for 7 years as a part of the Hawaii Ocean Time-series (HOT) program. The time-series data set displays an interannual increase in the inventory of surface ocean DIC which we interpret as a response to increasing atmospheric carbon dioxide concentrations. The rate of increase in surface ocean DIC at the open ocean HOT site is approximately 1 μmol kg−1 yr−1 with a 95% confidence interval of 0.72 to 1.37 μmol kg−1 yr−1. This accumulation rate is consistent with the rate of increase predicted from the rise in boundary layer pCO2.