Origin and Accumulation of an Anthropogenic CO2 and C-13 Suess Effect in the Arctic Ocean

Abstract

We determined the impact of anthropogenic CO2 (C-ant) accumulation on the delta C-13 of dissolved inorganic carbon in the Arctic Ocean (i.e., the C-13 Suess effect) based on delta C-13 measurements during a GEOTRACES cruise in 2015. The delta C-13 decrease was estimated from the amount of C-ant change derived by the transit time distribution approach and the ratio of the anthropogenic delta C-13/dissolved inorganic carbon change (RC). A significant C-ant increase (up to 45 mu mol kg(-1)) and delta C-13 decrease (up to -0.9 parts per thousand) extends to similar to 2,000 min 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 parts per thousand(mu mol 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 mu mol 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 delta C-13 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 CO2 uptake within the Arctic Basin. We determine the preindustrial delta C-13 (delta(CPI)-C-13) distributions and find distinct delta(CPI)-C-13 signatures of the intermediate and upper halocline waters that reflect the difference in delta(CPI)-C-13-PO4 relationship of Atlantic and Pacific source water.