Deriving a sea surface climatology of CO2 fugacity in support of air-sea gas flux studies.

Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean Carbon Dioxide (CO₂) Atlas (SOCAT) has made millions of global underway sea surface measurements of CO₂ publicly available, all in a uniform format and presented as fugacity, f_CO2. f_CO2 is highly sensitive to temperature and the measurements are only valid for the instantaneous sea surface temperature (SST) that is measured concurrent with the in-water CO₂ measurement. To create a climatology of f_CO2 data suitable for calculating air-sea CO₂ fluxes it is therefore desirable to calculate f_CO2 valid for climate quality SST. This paper presents a method for creating such a climatology. We recomputed SOCAT's f_CO2 values for their respective measurement month and year using climate quality SST data from satellite Earth observation and then extrapolated the resulting f_CO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly f_CO2 distributions for 2010. The partial pressure of CO₂ (p_CO2) is also provided for those who prefer to use p_CO2. The CO₂ concentration difference between ocean and atmosphere is the thermodynamic driving force of the air-sea CO₂ flux, and hence the presented f_CO2 distributions can be used in air-sea gas flux calculations together with climatologies of other climate variables. [ABSTRACT FROM AUTHOR]