Since the oceanic intake of carbon dioxide is limited, CO influx can also be described by the Revelle factor.  The Revelle Factor is a ratio of the change of carbon dioxide to the change in dissolved inorganic carbon, which serves as an indicator of carbon dioxide dissolution in the mixed layer considering the solubility pump.  The Revelle Factor is an expression to characterize the thermodynamic efficiency of the DIC pool to absorb CO into bicarbonate. The lower the Revelle factor, the higher the capacity for ocean water to take in carbon dioxide. While Revelle calculated a factor of around 10 in his day, in a 2004 study data showed a Revelle factor ranging from approximately 9 in low-latitude tropical regions to 15 in the southern ocean near Antarctica.