Slow release of fossil carbon during the Paleocene-Eocene Thermal Maximum: model inversion of a new, high-resolution carbon isotope record from Spitsbergen

Abstract

The Palaeocene-Eocene Thermal Maximum is a transient global warming event that occurred ~55.9 million years ago. Sedimentary carbon isotope records indicate that the event was produced by a massive release of carbon to the atmosphere/ocean system, thus an ancient analogue for future climate response to carbon dioxide (CO2) emission from fossil-fuel burning. However, the source, rate, and total amount of carbon input to the ocean and atmosphere at the time remain poorly known. Here we present isotopic and geochemical data from a highly expanded marine sedimentary section in Spitsbergen that provides an exceptional level of temporal resolution and completeness of the carbon isotopic excursion recorded in organic matter deposited during the PETM. Total organic carbon δ13C valuesconstrain the magnitude of the carbon isotope excursion in the ocean-atmosphere system to ~ 4‰. We force an earth system model of intermediate complexity (EMIC) to conform to the isotope record, and thereby determine a continuous estimate of variations in the rate of carbon addition. We find that despite uncertainty in the isotopic composition of the source and the duration of the event, the peak rate of carbon addition was likely much slower (0.3-1.7 Pg C yr-1) than the current fossil-fuel burning rate.