Fossil Corals Shed Light on Earth's Ancient Climate

Fossil corals are revealing a bit more about Earth's climate in the past. Scientists have used radiocarbon measured in deep-sea fossil corals to shed light on carbon dioxide (CO2) levels during Earth's last deglaciation.

About 18,000 to 11,000 years ago, Earth's climate system experienced a dramatic shift in a period known as the last deglaciation. During this period, atmospheric CO2 concentration increased by 80 parts per million (ppm), accompanied by sea level rise of almost 120 meters due to ice sheet melting and global warming.

Recent high-resolution ice core CO2 records have revealed that there were three abrupt centennial-scale atmospheric CO2 increases of about 10 ppm superimposed on the more gradual millennial-scale deglacial CO2 rise. The second and third of these events also coincided with abrupt warming of the high latitude North Atlantic region.

In addition, the measurements revealed two massive transient events where the water became homogenized and enriched in radiocarbon in the mid-depth equatorial Atlantic and the Drake Passage. This occurred in phase with the second two abrupt increases of the atmospheric CO2 concentration during the last deglaciation.

"Our radiocarbon data are consistent with two transient and enhanced deep Atlantic overturning events which flushed out respired carbon in the deep water, causing a rapid rise of atmospheric CO2 concentration and abrupt warming of the high latitude North Atlantic," said Tianyu Chen, one of the researchers, in a news release.

The findings reveal what the climate was like in the distant past. In addition, they show just what type of climate we might expect in the future.

The findings are published in the journal Science.

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