THE CONSEQUENCES OF RAPID EMISSIONS OF CARBON ON CLIMATE AND OCEAN CHEMISTRY: INSIGHTS FROM THE LATE PALEOCENE AND EARLY EOCENE

The climatic response to sudden changes in global carbon fluxes in the distant past is of great interest to the earth sciences community, particularly given the relevance of such events to understanding the long-term impacts of current and future anthropogenic carbon emissions on climate and ocean chemistry. The Paleogene is characterized by several such events, including the Paleocene-Eocene Thermal Maximum (PETM), which involved the release of a large mass of carbon to the ocean-atmosphere at the end of the Paleocene. The rate of release is estimated to have been roughly a Pg C/y with more 4500 Pg C in total, thus providing a unique opportunity to explore climate sensitivity to extreme greenhouse forcing, as well as the short- and long-term oceanic carbon cycle feedbacks. To this end, considerable time and effort have been invested over the last two decades to reconstruct the scale and timing of the climatic and carbon cycle changes associated with the PETM, and to integrate these observations with modeling. This includes efforts to ; 1) quantify the changes in sea surface temperatures (DSST) on a global scale; 2) place the PETM and other early Eocene hyperthermals in the context of longer-term background variability related to variations in Earth’s orbit (i.e., cycle stratigraphy): and 3) quantify the changes in ocean carbonate chemistry, particularly pH. For example, the reconstructions of SST have improved significantly with the development and application of the archeal lipid-based TEX₈₆ proxy, particularly in high latitude sections. Efforts to build high-resolution marine isotope records have benefitted from the recovery and study of highly expanded and continuous pelagic sedimentary sections, which now provide a high-fidelity orbital framework for the timing of the PETM and other similar events. And finally, the recent development and application of pH proxies, B/Ca and B isotopes in foraminifera from deep sea and shallow marine sections spanning the P-E boundary, provide the first unequivocal evidence for reductions in surface ocean pH. In this presentation i review several of these critical new developments.