The temperature dependence of pH in surface seawater

The temperature dependence of pH in surface seawater was investigated as a function of salinity and CO2 composition using the most recent values for the equilibrium constants of the CO2 system in seawater. A substantial discrepancy was found in one of the previously published algorithms used to correct shipboard pH measurements made at 25°C to the in situ temperature. Over the range of values expected in oceanic surface waters, both salinity and total alkalinity affected the pH temperature correction to a small extent (ΔpH<0.0017). However, by using salinity to estimate the total alkalinity, the error in the calculated pH temperature correction is reduced to less than 0.0002 pH unit over the temperature range 0–40°C.