Geologists pinpoint source of major global warming event more than 55 million years ago

November 18, 1999

For the first time, a team of scientists has identified the possible methane release site and critical sequence of events that precipitated Earth's bout with global warming, and the extinction of many deep-sea species and appearance of new mammalian orders, more than 55 million years ago.

The research project is part of the international Ocean Drilling Program, which is funded by the National Science Foundation (NSF) and a consortium of international partners.

In an article to be published this week in the journal Science, geologists Miriam Katz and Kenneth Miller of Rutgers University in New Brunswick, New Jersey, provide support for a link between the mass extinction millions of years ago and the massive release of methane and carbon dioxide into the earth's oceans and atmosphere, which is not unlike the present input of fossil fuels into the environment. "We haven't studied these major carbon influxes before because we didn't know about them," says NSF's Paul Dauphin, associate program director for ODP.

In what is known as the latest Paleocene thermal maximum (LPTM), Earth's climate and oceans warmed significantly about 55.5 million years ago. Numerous mammalian orders appeared while many deep-sea species became extinct as water temperatures soared by 4 to 8 degrees Celsius. Since the 1980s, scientists have tried to explain the rapid climate warming apparent in geochemical records from around the world.

"One approach to unraveling the possibilities of future climate change is to study analogs from the Earth's past," says Katz. "We have examined clues in the geologic record of an ancient massive release of carbon into the Earth's oceans and atmosphere." The clues came from analyzing certain geochemical and faunal changes in a group of microfossils known as foraminifera - essentially amoebas with shells - in order to reconstruct ancient oceanographic and climatic conditions.

Working as part of an international scientific team onboard the Ocean Drilling Program's vessel the JOIDES (Joint Oceanographic Institutions for Deep-Earth Sampling) Resolution, the researchers recovered ocean sediments from the Blake Nose, 400 kilometers (250 miles) east of Tallahassee, Florida. Katz and her co-authors have pinpointed this region as the first location to be identified as a possible LPTM methane release site, where methane appears to have escaped from a pressure zone created by an underlying ancient reef.

Katz says "the triggering mechanism for methane release is still open to debate," making it impossible for scientists to predict whether a massive release from today's 14,000 gigaton marine gas hydrate reservoir could occur again.

"We know that 55.5 million years ago, carbon dioxide was added to the atmosphere at a rate comparable to present-day fossil fuel input, providing the potential for using past changes in carbon dioxide levels to shed light on future climate change possibilities," Katz believes.

National Science Foundation

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