T133 Volcanism, Impacts, Mass Extinctions, and Global Environmental Change II

Monday, 19 October 2009
1:30 PM - 5:30 PM
Portland Ballroom 253

BIOSPHERE RESPONSE TO VOLCANIC CO2 RELEASE: SIBERIAN TRAPS AND END-PERMIAN MASS EXTINCTION

Paper number: T133-1
Program: Technical Sessions
Time: 1:30 PM – 1:50 PM

Authors

Abstract

The response of the biosphere (ocean/atmosphere/biota) to volcanic injection of carbon dioxide undoubtedly depends on the rate and total amount of carbon added. This in turns depends on the CO2 content of the degassing magma and the type of crustal materials with which it interacts. For example, estimates of CO2 emission during the emplacement of the Siberian Traps, coincident with the major phase of end-Permian mass extinction, range as high as 100,000 Pg CO2. While this indeed is a considerable quantity of carbon, its impact on the biosphere depends on the duration of eruption. At present-day rates of volcanism (approximately 250 Tg CO2 per year), volcanoes emit this amount of CO2 in approximately 400,000 years. Thus, to substantially perturb the carbon cycle, atmospheric pCO2, climate, the acidity of the ocean and its redox state, the release of CO2 has to be over a considerably shorter interval.

Here we use an Earth system model of intermediate complexity, Genie-1, to quantitatively evaluate the marine biospheric response to a range of CO2 injection rates and total quantities that spans those proposed for the end-Permian event. We explore the sensitivity of this result to the assumed initial state of the biosphere: greenhouse vs. icehouse, to address the question of how important it was that the Late Permian was already a warm period in Earth history, high atmospheric O2 vs. low, and sluggish vs. intense ocean circulation, because of uncertainties in these states. We also determine the effect that a putative lack of seafloor carbonate buffer has on the system response for this time (and all previous times) before planktonic carbonate producers had evolved. From these experiments we establish critical threshold CO2 release rates and durations that are capable of causing environmental disturbances capable of mass extinction.