New research into the Paleocene-Eocene thermal maximum, PETM, by scientists based at the National Oceanography Centre in Southampton, have made what they believe to be the most accurate estimation of its time-frame yet, which has allowed them to narrow down its cause.
Measuring radio-isotopes of uranium and lead in the mineral zircon found in two historic volcanic ash deposits collected from two locations on the island of Spitsbergen, in the Svalbard Archipelago in the Arctic, allowed the scientists to rule out the possibility that the PETM was caused by eccentricity in the Earth’s orbit.
Orbital eccentricity – the amount an orbital body deviates from a perfect circle – was believed to be a possible explanation for the PETM, one of several hyperthermals which took place during the Cenozoic era which started about 65.5 million years ago. However, the new date for the Paleocene–Eocene boundary – between 55.728 and 55.964 million years ago, which the scientists believe to be the most accurate estimate to date – was the same time that the Earth’s orbit was more stable, and the sudden warming related to orbital eccentricity could not have been to blame.
“Determining exactly what triggered the PETM requires very accurate dating of the event itself, to determine whether it occurred during a known maximum in the Earth’s orbital eccentricity” explains Adam Charles, a University of Southampton PhD student supervised by Dr Ian Harding, and first author of the newly published report.
“Compared to other early Eocene hyperthermals, it appears that the PETM was triggered by a different mechanism, and thus may have involved volcanism. However, a thorough test of this hypothesis will require further detailed dating studies,” concluded Charles.
Exactly what triggered the PETM is still a mystery, but ruling out orbital eccentricity helps scientists grow closer to understanding more about one of the best analogues we have to future global warming.