Ocean Acidification - Carbon Cycle

Carbon Cycle

The carbon cycle describes the fluxes of carbon dioxide (CO₂) between the oceans, terrestrial biosphere, lithosphere, and the atmosphere. Human activities such as the combustion of fossil fuels and land use changes have led to a new flux of CO₂ into the atmosphere. About 45% has remained in the atmosphere; most of the rest has been taken up by the oceans, with some also taken up by terrestrial plants.

The carbon cycle involves both organic compounds as well as inorganic carbon compounds such as carbon dioxide and the carbonates. The inorganic compounds are particularly relevant when discussing ocean acidification for it includes the many forms of dissolved CO₂ present in the Earth's oceans.

When CO₂ dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (CO_2(aq)), carbonic acid (H₂CO₃), bicarbonate (HCO−
3) and carbonate (CO2−
3). The ratio of these species depends on factors such as seawater temperature and alkalinity (as shown in a Bjerrum plot). These different forms of dissolved inorganic carbon are transferred from an ocean's surface to its interior by the ocean's solubility pump.

The resistance of an area of ocean to absorbing atmospheric CO₂ is known as the Revelle factor.