Ancient Global Warming Linked to Volcanic Eruptions
Findings published in this week's edition of Science reveal a link between massive volcanic eruptions and ancient global warming. The international team of researchers used rock dating to relate a sudden 5°C warming 56 million years ago, known as the Paleocene-Eocene thermal maximum (PETM), to major volcanic events occurring at the beginning of the PETM.
"There has been evidence in the marine record of this period of global warming, and evidence in the geologic record of the eruptions at roughly the same time, but until now there has been no direct link between the two," said Robert A. Duncan, a professor in the College of Oceanic and Atmospheric Sciences at Oregon State University and one of the authors of the study. The other authors of the study are Michael Storey, from Roskilde University, Denmark, and Carl C. Swisher, from Rutgers University.
The PETM was thought to have lasted approximately 200,000 years, and was accompanied by the large changes in carbon-isotope (the different forms of carbon found in nature) composition of the oceans, as well as ocean acidification and extinction of 30-50% of deep-sea species. The major eruptions that occurred at the beginning of the PETM are known as large igneous province (LIP) eruptions, which release many times more magma and greenhouse gases including carbon dioxide and methane than a single volcanic eruption.
In this study, researchers looked at a LIP called the North Atlantic Igneous Province (NAIP), which spans the North Atlantic from Greenland to Great Britain.
By analyzing rock samples from the NAIP and volcanic ash from marine sediment off the coast of Great Britain with evidence of the PETM, the researchers were able to determine a relationship between the volcanic eruptions and the PETM.
Duncan and his colleagues used argon-argon dating to determine the age of rocks from the NAIP and from marine volcanic ash associated with the PETM. The researchers placed the beginning of PTEM at 55.6 million years ago, and the NAIP eruptions at 56.1 million years ago.
The scientists speculate that the release of greenhouse gases by the volcanic eruptions led to the sudden global warming and changes in the ocean ecosystem. The results of the study may help to provide a model for today's climate change.
Written by Charles Tran