Global Carbon Cycle Perturbations and Implications for Arctic Hydrology during the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM; ca. 55.9 Ma) was an interval of geologically abrupt global warming lasting ~200 ka. It has been proposed as an ancient analogue for future climate response to CO₂ emission from fossil fuel burning. The onset of this event is fueled by a large release of ¹³C-depleted carbon into the ocean-atmosphere system. However, there is a large discrepancy in the magnitude of the carbon isotope excursion (CIE) between marine and terrestrial records. Here we present new organic geochemical data and stable carbon isotope records from n-alkanes and pristane extracted from core materials representing the most expanded PETM section yet recovered from a nearshore marine early Cenozoic succession from Spitsbergen. The low hydrogen index and oxygen index indicate that organic matter has been thermally altered, consistent with n-alkanes that do not show a clear odd-over-even predominance as reflected by the low and constant carbon preference index. The δ¹³C records of long chain n-alkanes from core BH9-05 track the δ¹³C recorded in total organic carbon, but are ~3% more negative prior to the CIE, ~4.5% more negative during the CIE, and ~4% more negative after the CIE. An orbital age model derived from the same core suggests the CIE from n-alkanes appears more abruptly onset than the bulk organic carbon, indicating possibly climate-induced modification to the observed feature in n-alkanes. In addition, the carbon isotope values of individual long-chain (n-C₂₇ to n-C₃₁) n-alkanes tend to become less negative with increasing chain length resulting in the smallest magnitude CIEs in longer chain lengths (i.e. n-C₃₁) and the largest magnitude CIEs in shorter chain lengths (i.e. n-C₂₇). We are currently considering the effect of plant community and paleoclimate on the observed pattern of CIE in n-alkanes to evaluate carbon cycle perturbations and Arctic hydrology changes during the PETM. One interpretation of these patterns is that there was an increased precipitation in response to the warming in the Arctic region.