The Indian Ocean C-13 Suess effect

The delta(13)C of dissolved inorganic carbon (DIC) decrease (the C-13 Suess effect) in the Indian Ocean was calculated using a multiparameter linear regression comparison of the 1978 Geochemical Ocean Sections Study and 1995 World Ocean Circulation Experiment delta(13)C of DIG, hydrographic, and nutrient data. The surface ocean delta(13)C decrease rate along 80 degrees and 115 degrees E ranged from approximately -0.1 parts per thousand decade(-1) at 55 degrees S to a maximum of approximately -0.18 parts per thousand decade(-1) at similar to 35 degrees S and decreased northward to around -0.13 parts per thousand decade(-1) at the equator. Using a global extrapolation based on ocean model results [Bacastow et al., 1996] and previous delta(13)C changes calculated from 1970 to 1993 station reoccupations in the Pacific Ocean and based on preformed delta(13)C versus chlorofluorocarbon age trends in the Indian, Pacific, and Atlantic Oceans [Sonnerup et al., 1999], an ocean-wide average surface ocean delta(13)C rate of change of -0.15 to -0.17 parts per thousand decade(-1) was estimated. The average depth-integrated delta(13)C change rate between 1978 and 1995 along 80 degrees and 115 degrees E was -6.9 +/- 0.5 parts per thousand m yr(-1) from 58 degrees S to 5 degrees N.