Oceans steeped in corrosive acid may sound like something out of a James Bond movie, but according to Ken Caldeira, an oceanographer at the Carnegie Institute, carbon dioxide emissions are in the process of making our seas so acidic that a widespread extinction of marine life may be inevitable.
When CO2 is emitted into the atmosphere, some of it dissolves into seawater, forming carbonic acid. As the amounts of CO2 released increases, the acidic content of the oceans grows higher and higher. This shift in pH can weaken the shells and skeletons of creatures like coral, clams and sea snails.
“At high enough concentrations the carbonic acid is corrosive to coral reefs and animals that make their shells or skeletons from calcium carbonate,” Caldeira said.
While volcanoes and other natural sources release CO2 into the atmosphere constantly, they cause only minimal shifts in the levels of carbonic acid in the ocean. Currently, human emissions of CO2 are about 50 times the natural rate. Because of this, agreements like the Kyoto Protocol, which aim to reduce CO2 emissions to below 1990 rates—still exponentially higher than the level of natural CO2 emissions—seem largely ineffective to Caldeira.
“I think the idea of stabilizing emissions or slightly reducing emissions is far too unambitious,” he said.
If we do not accomplish a severe reduction, according to Caldeira, we may lose all calcium carbonate-based life in the oceans by the next century.
The last time Earthís oceans underwent such a significant chemical change was at the Cretaceous-Tertiary boundary, the period when non-avian dinosaurs died out 65 million years ago. Caldeira said that an asteroid hit Earth in Chicxulub, Mexico, releasing sulfur dioxide that rained down in sulfuric acid on the oceans and caused ecological damage that was almost irreparable, annihilating many marine species.
“The pattern of extinction shows that organisms with shells or skeletons made out of calcium carbonate shells preferentially went extinct,” Caldeira said. ìIt took coral reefs something like two million years to come back.î
Caldeira presented his findings last week at the 2006 Ocean Sciences Conference in Honolulu, HI.
Originally published February 28, 2006