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Air-sea gas exchange is a physico-chemical process, primarily controlled by the air-sea difference in gas concentrations and the exchange coefficient, which determines how quickly a molecule of gas can move across the ocean-atmosphere boundary. It takes about one year to equilibrate CO2 in the surface ocean with atmospheric CO2, so it is not unusual to observe large air-sea differences in CO2 concentrations. Most of the differences are caused by variability in the oceans due to biology and ocean circulation. The oceans contain a very large reservoir of carbon that can be exchanged with the atmosphere because the CO2 reacts with water to form carbonic acid and its dissociation products. As atmospheric CO2 increases in the future, the interaction with the surface ocean will change the chemistry of the seawater. The total dissolved inorganic carbon (DIC) content of the waters will increase. Because CO2 is an acid gas, the carbonate ion (CO32-) concentration and pH of the surface waters will decrease. The physiological effects of these changes on ocean biology are not fully understood, but studies have suggested that these changes may decrease calcification rates in coccoliths, corals, and coralline algae.
The PMEL carbon group participates in a growing network of surface ocean observations aimed at monitoring and evaluating the surface ocean CO2 changes and understanding the potential environmental consequences of these changes.
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