Who would have thought? :)
GLOBAL WARMING
Ancient eruptions of carbon dioxide traced to oceans
Researchers say the gas may have accelerated Earth's warming after an ice age.
By Alan Zarembo
Times Staff Writer
May 11, 2007
The oceans burped … twice.
About 13,000 and 18,000 years ago, carbon dioxide poured into the atmosphere in two giant belches that drove concentrations of the greenhouse gas from 180 to 265 parts per million, where it held relatively steady until the Industrial Revolution.
Scientists have long known about the jump in gas levels from looking at ice cores. They suspected the carbon dioxide originated in a deep, carbon-rich reservoir in the oceans but had no way to explain how the gas could accumulate and then be released so suddenly.
Reporting in the journal Science today, researchers said they found the answer in a sample of sediment drilled in the Pacific Ocean.
"This new study nails it," said J.R. Toggweiler, an oceanographer at the National Oceanographic and Atmospheric Administration, who was not involved in the study. "If there were any doubters, I don't think they have a leg to stand on."
The researchers first correlated the bands of sediments in the core drilled off Baja to the Greenland ice cores. That allowed them to create a matching timeline over the last 38,000 years.
Embedded in the 50-foot-long Baja core were shells left by bottom-dwelling microorganisms. The researchers analyzed the shells to determine the ratio of two isotopes, carbon-12 and carbon-14.
Carbon-14 is produced by cosmic rays in the atmosphere. Thus, water that stays deep in the oceans for thousands of years contains relatively little carbon-14 and lots of carbon-12.
The researchers found two periods that stood out for low carbon-14 levels.
The levels meant that the water during those periods was barely circulating to the surface. Carbon from decaying organic material was accumulating in the deep. The old water eventually rose to the surface, releasing its carbon dioxide in an enormous burp.
Each of the gas releases was recorded in the Greenland ice cores.
