Global relationships of total inorganic carbon with temperature and nitrate in surface seawater

High quality total inorganic carbon ( C T ) measurements made in the major ocean basins as part of the Joint Global Ocean Flux Study (JGOFS), the National Oceanic and Atmospheric Administration/Ocean Atmosphere Carbon Exchange Study (NOAA/OACES), and the Department of Energy/World Ocean Circulation Experiment (DOE/WOCE) programs are related to sea surface temperature (SST) and nitrate (NO 3 − ). A simple two‐parameter function with SST and NO 3 − of the form NC T = a + b SST + c SST 2 + d NO 3 − fits salinity ( S )‐normalized surface C T ( NC T = C T × 35/ S ) data for different parts of the oceans within an area‐weighted error of ±7 μmol kg −1 (1σ). Estimated values of NC T using the derived algorithms with NO 3 − and SST are compared with values calculated from the surface partial pressure of CO 2 ( p CO 2sw ) [ Takahashi et al., 1997] and total alkalinity ( A T ) [ Millero et al. , 1998] fields using thermodynamic models. Comparisons of the estimated values of NC T with measurements not used to derive the same algorithms, and comparisons with the values calculated from global A T and p CO 2sw fields, give a realistic uncertainty of ±15 μmol kg −1 in estimated C T . The derived correlations of NC T with SST and NO 3 − presented here make it possible to estimate surface C T over the ocean from climatological SST, S , and NO 3 − fields.