Correction of f(CO2) for Warming of the Surface Seawater
The next calculation is the correction of the fugacity in the moist equilibrator vapor to the in situ fugacity of CO2 in equilibrium with the surface seawater. Since the water in the equilibrator has warmed in transiting from the bow inlet line of the ship up to the equilibrator, a correction must be applied for this warming. The equation which simultaneously describes the temperature dependence of CO2 solubility and carbonate equilibria is given by equation (16) in the main text from Weiss et al. (1982):
ln f(CO2)/t=0.03107-2.785 · 10-4t-1.839 · 10-3 ln f(CO2) (eq. 27)
In the case of evaluating the warming correction of seawater in transiting to the equilibrator, ln f(CO2)/t is the change in the logarithm of the measured fugacity in moist air for an incremental change in the equilibrator temperature.
This calculation gives the fugacity reported in the data file for f(CO2) in surface seawater, i.e., the fugacity of CO2 in moist air at the sea surface conditions.