Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum
Ying Cui¹*, Lee R. Kump¹, Andy J. Ridgwell², Adam J. Charles³, Christopher K. Junium¹, Aaron F. Diefendorf¹, Katherine H. Freeman¹, Nathan M. Urban¹ and Ian C. Harding³
Abstract
The transient global warming event known as the Palaeocene–Eocene Thermal Maximum occurred about 55.9 Myr ago. The warming was accompanied by a rapid shift in the isotopic signature of sedimentary carbonates, suggesting that the event was triggered by a massive release of carbon to the ocean–atmosphere system. However, the source, rate of emission and total amount of carbon involved remain poorly constrained. Here we use an expanded marine sedimentary section from Spitsbergen to reconstruct the carbon isotope excursion as recorded in marine organic matter. We find that the total magnitude of the carbon isotope excursion in the ocean–atmosphere system was about 4°/oo. We then force an Earth system model of intermediate complexity to conform to our isotope record, allowing us to generate a continuous estimate of the rate of carbon emissions to the atmosphere. Our simulations show that the peak rate of carbon addition was probably in the range of 0.3–1.7 Pg C/yr, much slower than the present rate of carbon emissions.
The Conclusion's money paragraph:
"The quantities of carbon added during the PETM span the estimates of current fossil-fuel resources, suggesting that the PETM could serve as a good analogue for future warming. However, the peak rates of PETM carbon addition in these simulations (also see refs 9, 15 and 25), and in complementary simulations based on other published isotope records, are a small fraction of the present rate of fossil-fuel burning. Thus, although the current overall capacity for society to perturb the carbon cycle is comparable to that of the PETM, the rate at which we are imposing the current perturbation on the Earth system may be unprecedented."
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