Decadal-Scale Increase of Anthropogenic CO2 in Antarctic Bottom Water in the Indian and Western Pacific Sectors of the Southern Ocean

摘要

We determined decadal-scale increases of anthropogenic CO2 in the water column using data sets collected 17 years apart (1994-1996 and 2012-2013) along a transect at nominal 62 degrees S in the Indian and western Pacific sectors of the Southern Ocean. Large increases of anthropogenic CO2 (up to 9.1 +/- 1.5 mu mol/kg), closely following atmospheric CO2 increases, were found in Antarctic Bottom Water (AABW), previously considered a small sink of anthropogenic CO2. Vertical distributions of anthropogenic CO2 increases showed significant positive correlations with those of changes in CFC-12 and SF6, implying that the distributions were mainly controlled by physical processes such as ventilation and circulation. Calculated uptake rates of anthropogenic CO2 by AABW were between 0.29 and 0.39 mol.m(-2).yr(-1) in five longitudinal segments of the transect. In accounting for the large increase of anthropogenic CO2 in AABW, sea surface conditions in the formation region of AABW are important.