In the ‘solubility pump’ CO₂ is transferred from air to sea by gas exchange as Dissolved Inorganic Carbon (DIC, defined as CO₂ plus bicarbonate and carbonate ions) as seawater is undersaturated with CO₂ compared to the atmosphere. The CO₂ is subsequently distributed by mixing and ocean currents. The process is more efficient at higher latitudes as the uptake of CO₂ as DIC increases at lower temperatures since the solubility of CO₂ increases in cold water. Dense water formed below pancake ice, as for example in the Greenland Sea, sinks rapidly to the deep ocean taking with it much higher concentrations of DIC. In such regions of deep water formation, carbon is delivered at high concentrations to the deep ocean where the deep circulation (the ‘global conveyor belt ’) carries it around the world and keeps it out of contact with the atmosphere for up to 500 years. In consequence there is a steep vertical gradient in the concentration of DIC and it has been estimated that about 25% to 50% of this gradient may be contributed by the solubility pump. Expected future changes in the ocean (e.g. circulation, temperature, pH) due to climate change are likely to alter the functioning of both the solubility and biological pumps. If the natural carbon cycle in the ocean reduced or ceased to operate and the stored carbon were re-equilibrated with the atmosphere, current concentrations would increase substantially.