Abstract
Compared with historically accumulated hydrographic and nutrients measurements taken at
sea, total inorganic carbon dioxide (TCO2) data are far from enough to produce a gridded map
ping of high resolution on a global scale, which is crucial to evaluate the carbon budget in the
oceans and provide initial values to constrain the biochemical models. In order to get a better
understanding of TCO2in the oceans and contribute the large historical database to TCO2estima
tion, TCO2 properties and its relation with nutrients in the world oceans are presented and dis
cussed using ship data from several international programs, especially recent WOCE cruises dur
ing which the accuracy of TCO2 measurements are believed to have been significantly improved.
Based on these, a new parameterization method is proposed and tested to estimate TCO2 below
the upper oceans (＞ 400 m) where its seasonal variations are comparatively small. Compared with
the ship data which have not been involved in the parameterization procedure, the mean bias and
standard deviation are 0.8 u.mol/kg and 7.0 u.mol/kg respectively for Pacific Ocean, while they are
0.5 u.mol/kg and 5.4 u.mol/kg respectively for Atlantic Ocean. Calculated TCO2 in the global
oceans can be obtained at Levitus grid point (1°x1°) from 400 m down to the depth of 5,500 m,
including vast ocean areas where field investigations ofTCO2 have never been performed.
