Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean

We report four profiles of the radiocarbon content of dissolved organic carbon (DOC) spanning the South Indian Ocean (SIO), ranging from the Polar Front (56 degrees S) to the subtropics (29 degrees S). Surface waters held mean DOC Delta C-14 values of -4266 (similar to 4,400 C-14 years) at the Polar Front and DOC Delta C-14 values of -25222 (similar to 2,000 C-14 years) in the subtropics. At depth, Circumpolar Deep Waters held DOC Delta C-14 values of -491 +/- 13 parts per thousand (similar to 5,400 years), while values in Indian Deep Water were more depleted, holding DOC Delta C-14 values of -503 +/- 8 parts per thousand (similar to 5,600 C-14 years). High-salinity North Atlantic Deep Water intruding into the deep SIO had a distinctly less depleted DOC Delta C-14 value of -481 +/- 8 parts per thousand (similar to 5,100 C-14 years). We use multiple linear regression to assess the dynamics of DOC Delta C-14 values in the deep Indian Ocean, finding that their distribution is characteristic of water masses in that region.