Partial Pressure of CO2 (pCO2)
D1. Physical and chemical oceanography and marine meteorologyDefinition
Pressure that CO2 in seawater would exert in equilibrium with the gas phase.
The partial pressure of CO2 (pCO2) is the pressure dissolved CO2 in seawater would exert in equilibrium with the air, the variable whose ocean-atmosphere difference drives air-sea CO2 flux. Where surface pCO2 is below the atmospheric value (about 420 microatmospheres) the ocean absorbs CO2; where it is higher, in upwelling and warm tropical water, it outgasses. Underway and mooring pCO2 systems map the ocean carbon sink.