Wednesday, January 31st, 2018

Wednesday Seminar

4:10 PM, 55 Roessler
Tea and cookies at 3:45 in the aviary - (2110 EPS)

“Paleocene-Eocene Thermal Maximum meets the North Atlantic Igneous Province: Coincidence or global environmental conspiracy?”

      – by Dr. Andy Ridgwell, Department of Earth Sciences, UC Riverside

The Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), with its multiple lines of
attendant evidence for massive greenhouse gas release and global-scale warming, is
regarded as a highly plausible future analogue. However, because the onset of the PETM
likely took place at a rate at least one, if not two, orders of magnitude slower than current
century-scale anthropogenic warming, it is uncertain what we can learn e.g. re. biotic
sensitivities, except perhaps to place a lower limit on potential future disruption. Instead,
focus has often been on what the PETM might reveal regarding the sensitivity of surficial,
reduced carbon stores (e.g. vegetation and soil carbon, permafrost, marine hydrates) to
warming, and hence the strength of positive feedbacks between atmospheric CO2 and
climate change. Indeed, almost all explanations to date for the PETM have relied either
solely, or dominantly, on one or more of these carbon sources and feedbacks. Yet one of the
largest igneous provinces (the North Atlantic Igneous Province — ‘NAIP’) recorded in the
geological record was being emplaced exactly at this time and its role to date, almost entirely,
overlooked.
Here I present a revised view of the PETM as one predominantly the product of massive
volcanism, making it rather unexpectedly more like the end Permian in character. Feedbacks
with climate and involving reservoirs of reduced organic carbon likely only play a more minor
role, reducing the event’s future relevance. I come to these conclusions on the basis of new
paired records of boron and carbon isotope changes, assimilating these data in an Earth
system model to reconstruct the unfolding carbon cycle dynamics across the event. Model
results indicate >10,000 PgC with an average isotopically heavier than -17‰ is required to
account for the observations, leading to the identification of volcanism associated with the
NAIP as the main driver of the PETM.

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