CO Solubility Pump

Solubility Pump: Many different gases dissolve in seawater including oxygen, nitrogen and carbon dioxide. Solubility of CO₂ is strongly dependent on temperature, among other factors. The colder the water, the more CO₂ it can hold. Indeed, most of the CO₂ from atmospheric sources is dissolved in cold water of the high latitudes (particularly so in the north Atlantic) Each year, the global ocean absorbs about 25% of all carbon emitted into the atmosphere from human activities. 19 Alarmingly, the efficiency of seawater to dissolve CO₂ is expected to decrease as the ocean continues to warm. In polar regions, where solubility of CO₂ is high, sea ice formation leaves the surrounding waters very salty and dense. The dense water then sinks, generating a ‘thermohaline’ circulation that continuously moves water equatorward in the deep ocean (known as the global conveyor belt) Therefore, the deep sea stores vast quantities of dissolved inorganic carbon (DIC) on long timescales. T his process of atmospheric CO₂ dissolving and reacting in the sea surface to form DIC then being transported into the deep sea by wind and thermohaline circulation is known as the ‘solubility pump.’ It is important to note that CO₂ also outgasses back into the atmosphere (just as a carbonated beverage becomes flat after opening the container), therefore the balance of carbon between ocean and atmosphere is the important factor in relation to how much GHG is in the atmosphere at any given time. (Illustration by Natalie Renier, © Woods Hole Oceanographic Institution)