Optimal coefficients and standard deviations of a multiple linear regression fit of anthropogenic carbon concentrations estimated using lower and upper limits of the C:O ratio, to observed AOU and anthropogenic carbon as shown in Equation 8. Coefficient Low C:O High C:O _________________________________________________________________ alpha -6.0e-2 8.2e-2 beta 0.96 1.0 gamma (micromol kg-1) 5.3 -6.0 Standard Deviation (micromol kg-1) 1.93 1.94