[PAOCQ] Donald Penman (Utah State University)

“A dynamic climate and carbon cycle during the onset of the Paleocene-Eocene Thermal Maximum”

The Paleocene-Eocene Thermal Maximum (or PETM, 56 million years ago) is the largest rapid warming event of the Cenozoic. The event is marked by a global carbon isotope excursion, a wealth of paleotemperature estimates indicating 5-8 °C of surface warming globally, and geochemical and sedimentological evidence for abrupt ocean acidification. These lines of evidence all support a large, rapid release of carbon into the atmosphere as the main mechanism for PETM Earth System change – although the source of carbon and the proximal cause or trigger of the event are still a matter of vigorous debate. Estimates of the carbon release mass from carbon-cycle models are similar to proven modern fossil fuel reserves, which makes the PETM a useful point of comparison for future anthropogenic carbon release scenarios, but the rate of carbon release is debated and generally considered to be significantly slower than current anthropogenic emissions. A major limitation on understanding the sequence of events during the onset of the PETM is the temporal resolution and continuity of available sedimentary records of the event: the onset is often described as “geologically instantaneous,” which reflects the inability of existing sedimentary records to resolve the pace of warming or carbon isotopic shifts, or lead-lag relationships or any other dynamic behavior during the critical thousands of years at the beginning of the PETM. My talk will focus on the nature and causes of these limitations in existing marine and terrestrial sedimentary records, as well as how new records and analytical techniques are beginning to make progress. A more dynamic sequence of events now seems likely during the PETM onset, including a smaller “pre-onset excursion” in carbon isotopes and indications of significant warming before the “main event” associated with the PETM carbon isotope excursion.

PAOC Colloquium —

Interdisciplinary seminar series that brings together the whole PAOC (Program in Atmospheres, Oceans, and Climate) community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, as well as talks about societal impacts of climatic processes.

Contact: paoc-colloquium-comm@mit.edu