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

Abstract

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 and related to sea surface temperature (SST) and nitrate (NO3-). A simple two-parameter function with SST and NO3- of the form NC(T)= a + b SST + c SST2 + d NO3- fits salinity (S)-normalized surface C(T)(NC(T)=C(T)x35/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 NO3- and SST are compared with values calculated from the surface partial pressure of CO2 (pCO(2sw)) [Takabashi 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 pCO(2sw) fields, give a realistic uncertainty of ±15 μmol kg-1 in estimated C(T). The derived correlations of NC(T) with SST and NO3 presented here make it possible to estimate surface C(T) over the ocean from climatological SST, S, and NO3- fields.