THE LATE PALEOCENE THERMAL MAXIMUM: ANCIENT GLOBAL WARMING AT MODERN RATES?

One of the most abrupt and dramatic ancient global warming events took place ∼55 Ma in the late Paleocene epoch. This event, known as the Late Paleocene Thermal Maximum (LPTM), involved warming of high latitude and subtropical oceanic surface waters by up to 6°C and deep waters by up to 8°C. Deep-water warming and consequent oxygen deficiency led to the most severe mass extinction of deep-sea faunas in the last 90 million years. By contrast, the LPTM is also associated with major speciation of planktic foraminifers and terrestrial mammals. The event corresponds to a large (3 per mil), negative carbon isotope excursion (CIE) that suggests major changes in the nature of carbon cycling. The CIE has been used to correlate the LPTM between terrestrial and marine sediments. Current estimates of the duration of the LPTM range between 50–200 thousands of years. The onset of the event, including the full magnitude of the CIE, is thought to span 2–10 thousands of years. This initial rate of CO2 input is comparable with anthropogenic input of fossil fuels. Possible sources of CO2 and warming mechanisms include dissociation of methane hydrates along continental margins and a major episode of effusive volcanism in the North Atlantic. For causal mechanisms to be fully tested, however, more precise estimates of the duration of the onset are required. In this talk, a state-of-the-art chronology of the LPTM was presented along with a comparison of LPTM and modern CO2 input and warming rates. [ABSTRACT FROM AUTHOR]