Origin and Accumulation of an Anthropogenic CO<sub>2</sub> and <sup>13</sup>C Suess Effect in the Arctic Ocean
Young Ho Ko, Paul D. Quay
Abstract
Abstract We determined the impact of anthropogenic CO 2 (C ant ) accumulation on the δ 13 C of dissolved inorganic carbon in the Arctic Ocean (i.e., the 13 C Suess effect) based on δ 13 C measurements during a GEOTRACES cruise in 2015. The δ 13 C decrease was estimated from the amount of C ant change derived by the transit time distribution approach and the ratio of the anthropogenic δ 13 C/dissolved inorganic carbon change (RC). A significant C ant increase (up to 45 μmol kg −1 ) and δ 13 C decrease (up to −0.9‰) extends to ~2,000 m in the Canada and Makarov Basin. We find distinctly different RC values for the intermediate water (300–2,000 m) and upper halocline water (<200 m) of −0.020 and −0.012‰ (μmol kg −1 ) −1 , respectively, which identifies two sources of C ant accumulation from North Atlantic and North Pacific. Furthermore, estimated RC for intermediate waters is the same as the RC observed in the Greenland Sea and the rate of anthropogenic dissolved inorganic carbon increase estimated for intermediate waters at 0.9 μmol kg −1 yr −1 is identical to the estimated rate in the Iceland Sea. These observations indicate that the high rate of C ant accumulation and δ 13 C decrease in the Arctic Ocean is primarily a result of the input of C ant , via ventilation of intermediate waters, from the Nordic Sea rather than local anthropogenic CO 2 uptake within the Arctic Basin. We determine the preindustrial δ 13 C (δ 13 C PI ) distributions and find distinct δ 13 C PI signatures of the intermediate and upper halocline waters that reflect the difference in δ 13 C PI –PO 4 relationship of Atlantic and Pacific source water.