Massive and rapid predominantly volcanic CO2 emission during the
end-Permian mass extinction
Abstract
The end-Permian mass extinction event (~252 Mya) is associated with
one of the largest global carbon cycle perturbations in the
Phanerozoic and is thought to be triggered by the Siberian Traps
volcanism. Sizable carbon isotope excursions (CIEs) have been found at
numerous sites around the world, suggesting massive quantities of
13C-depleted CO2 input into the ocean and atmosphere system. The exact
magnitude and cause of the CIEs, the pace of CO2 emission, and the
total quantity of CO2, however, remain poorly known. Here, we quantify
the CO2 emission in an Earth system model based on new
compound-specific carbon isotope records from the Finnmark Platform
and an astronomically tuned age model. By quantitatively comparing the
modeled surface ocean pH and boron isotope pH proxy, a massive
(~36,000 Gt C) and rapid emission (~5 Gt C yr-1) of largely volcanic
CO2 source (~-15%) is necessary to drive the observed pattern of CIE,
the abrupt decline in surface ocean pH, and the extreme global
temperature increase. This suggests that the massive amount of
greenhouse gases may have pushed the Earth system toward a critical
tipping point, beyond which extreme changes in ocean pH and
temperature led to irreversible mass extinction. The comparatively
amplified CIE observed in higher plant leaf waxes suggests that the
surface waters of the Finnmark Platform were likely out of equilibrium
with the initial massive centennial-scale release of carbon from the
massive Siberian Traps volcanism, supporting the rapidity of carbon
injection. Our modeling work reveals that carbon emission pulses are
accompanied by organic carbon burial, facilitated by widespread ocean
anoxia.
https://www.pnas.org/content/118/37/e2014701118
Temporal Scaling of Carbon Emission and Accumulation Rates: Modern
Anthropogenic Emissions Compared to Estimates of PETM Onset
Accumulation
Abstract
The Paleocene-Eocene thermal maximum (PETM) was caused by a massive
release of carbon to the atmosphere. This is a benchmark global
greenhouse warming event that raised temperatures to their warmest
since extinction of the dinosaurs. Rates of carbon emission today can
be compared to those during onset of the PETM in two ways: (1)
projection of long-term PETM rates for comparison on an annual time
scale and (2) projection of short-term modern rates for comparison on
a PETM time scale. Both require temporal scaling and extrapolation for
comparison on the same time scale. PETM rates are few and projection
to a short time scale is poorly constrained. Modern rates are many,
and projection to a longer PETM time scale is tightly
constrained—modern rates are some 9–10 times higher than those during
onset of the PETM. If the present trend of anthropogenic emissions
continues, we can expect to reach a PETM-scale accumulation of
atmospheric carbon in as few as 140 to 259 years (about 5 to 10 human
generations).
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018PA003379