Marine fossils help scientists study ancient period of global warming

Jan. 9 (UPI) -- If CO2 emissions continue unabated, global temperatures could increase by more than three degrees Celsius. Earth experienced similar temperature increases during the Miocene Climate Optimum, a period of global warming between 15 and 17 million years ago.

Scientists have struggled to identify the cause of this period of global warming and its effects on Earth's environment. However, new analysis of marine fossils has helped scientists draw connections between volcanic activity and temperature increases during the Miocene Climate Optimum.


"Our planet has been warm before," researcher Carrie Lear, a professor of Earth sciences at Cardiff University, said in a news release. "We can use ancient fossils to help understand how the climate system works during these times."

By studying the ancient biochemical signals trapped in fossils, recovered from sediment cores retrieved from the Pacific, Atlantic and Indian oceans, scientists were able to estimate temperature and carbon levels in the ocean during the Miocene Climate Optimum.

Scientists already knew that volcanic formations in the Pacific Northwest of the United States, the so-called Columbia River flood basalts, erupted around the same time as the Miocene Climate Optimum. The period also featured a large increase in the burial of carbon-rich organisms.


The latest research, published Thursday in the journal Nature Communications, suggests the eruptions triggered an increase in atmospheric CO2 and a decline in ocean pH levels. These chemical signatures suggest a rise in global temperatures precipitated sea level rise. As the ocean gets higher, causing an increase in coastal flooding, more and more organic material was eroded into and buried by ocean sediments.

"The elevated marine productivity and carbon burial helped to remove some of the carbon dioxide from the volcanoes and acted as a negative feedback, mitigating some, but not all, of the climatic effects associated with the outpouring of volcanic CO2," said Sindia Sosdian, lead study author and researcher at Cardiff University's School of Earth and Ocean Sciences.

Throughout the planet's history, some episodes of pronounced volcanic activity have resulted in mass extinctions. But like most periods of heightened volcanic activity, the eruptions of the Columbia River flood basalts and subsequent climatic effects did not, and now scientists know why.

"During the Miocene Climatic Optimum the response of the oceans and climate was remarkably similar to other massive volcanic eruptions in the geological record," said study co-author Tali Babila, an Earth scientist at the University of Southampton. "The presence of the Antarctic ice sheet and the relatively slow release of carbon however minimized the magnitude of environmental change and the associated consequences on marine life during this event."


While the latest research can help scientists better understand ancient periods of climate change, the authors of the new study suggests today's global warming is happening too fast to expect similar feedback loops to reduce CO2 emissions.

"We won't be able to rely on these slow natural feedbacks to counteract global warming," Sosdian said. "But this research is still important because it helps us understand how our planet works when it is in a warm mode."

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