19 Nov 2009:
Oceans’ Ability to Absorb CO2 May be Diminishing, New Study Says
A study of the accumulation of carbon dioxide in the world’s oceans from 1765 to the present shows that as humanity pumps more CO2 into the atmosphere, the capacity of the world’s oceans to continue absorbing carbon appears to be decreasing. Researchers from Columbia University and NASA estimate that since 2000, the proportion of fossil-fuel emissions absorbed by the oceans may have declined by as much as 10 percent. In effect, researchers say that industrial activity has been producing so much C02 since 1950 that the oceans are slowly becoming saturated with the gas. “The more carbon dioxide you put in, the more acidic the ocean becomes, reducing its ability to hold CO2,” said lead researcher Samar Khatiwala, an oceanographer at Columbia’s Lamont-Doherty Earth Observatory. The study, published in the journal Nature, estimated that the oceans currently hold about 150 tons of industrial carbon — a third more than in the 1990s. The researchers used data on ocean chemistry, salinity, temperature, and other measures to calculate the amount of industrial carbon in the ocean for the past 245 years. The study showed that the land may now being absorbing more carbon than it is producing, perhaps because higher atmospheric CO2 levels are increasing the rate of photosynthesis.