The process by which the ocean maintains a vertical gradient in DIC (CO2 plus bicarbonate and carbonate ions) – such that DIC is concentrated in the deep ocean – as a result of gas exchange. Surface water at equilibrium with a given CO2 concentration will increase its DIC concentration (uptake CO2) when the water temperature decreases since the solubility and dissociation of CO2 increase in cold water. The regions of deep water formation are located in high latitudes so the deep ocean is filled with cold water with relatively high DIC concentration. It is estimate that about 50% of the vertical DIC gradient can be accounted for by this process.