Thursday, January 1, 2009
OCEAN SCIENCE: Winter Carbonate Collapse
H. Jesse Smith
Anthropogenic fossil-fuel burning is increasing the concentration of CO2 in the atmosphere, which in turn is causing more CO2 to dissolve in the ocean, thereby lowering the water's pH. Such ocean acidification in turn decreases the concentration of carbonate ion (CO3)2-, which makes it more difficult for calcifying organisms such as foraminifera, pteropods, and corals to build their skeletons. So far, most of the attention paid to this process has focused on the time-averaged chemistry of the ocean, but organisms actually experience seasonal carbonate and pH variations. McNeil and Matear examine these variations and show that anthropogenic CO2 uptake is likely to induce winter aragonite undersaturation in some regions of the ocean when atmospheric CO2 levels reach 450 parts per million. These findings underscore the importance of understanding the seasonal dynamics of marine carbonate chemistry, as natural variability could hasten the deleterious impacts of future ocean acidification. -- HJS Proc. Natl. Acad. Sci. U.S.A. 105, 18860 (2008).