Among the natural carbon sinks in earth's biogeochemical system, the world's oceans play the dominant role in buffering changes in atmospheric CO2 concentrations. Covering 70% of the earth's surface, the oceans contain approximately 50 times the carbon present in the atmosphere. The annual carbon flux between the atmosphere and the oceans is approximately 100 Pg (100 billion metric tons) . The net uptake of CO2 by the global oceans, under non-El Nino conditions, has been estimated to be approximately 2 Pg C year-1 (2 billion metric tons) .
Atmospheric CO2 partitions into the ocean by dissolution and is, then, removed by either chemical ("solubility pump") or biological processes ("biological carbon pump")  . Amplifying these natural CO2 sequestration processes by changing the chemistry of the ocean surface has been proposed as a geoengineering strategy.
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