| Understanding how rapid warming affects global precipitation patterns during periods of global warming is essential to forecasting the impact of future climate change. The early Eocene (~55-52 Ma) represents a period of peak warmth during the past 65 million years, with global temperatures ~5-10°C warmer than present. This period is also known for at least three greenhouse gas-induced episodes of rapid global warming (i.e., hyperthermals: PETM, ~55 Ma; ETM2, ~53.7 Ma; and ETM3, 52.8 Ma), often considered as extreme analogues of modern climate change. Hyperthermals are also characterized by negative carbon isotope excursions (CIE), which reflect the input of isotopically light carbon responsible for observed temperature increases. The hydrogen isotopic composition of compound-specific biomarkers preserved in the sedimentary record is a novel proxy used for paleo-hydrological reconstructions. In this dissertation, I first explore the robustness of isotopic expression of high-latitude hydrological change during rapid warming by comparing two separate hyperthermals from Lomonosov Ridge (Arctic). Next, I assess biomarker records from two sections located in close proximity in the Belluno Basin (Italy) to evaluate intra-basinal variability in isotopic records. Finally, all existing n-alkane records to date are compiled and evaluated within a modeling framework to investigate how global hydrology changed prior to and during the PETM.;The isotopic compositions of PETM n-alkanes (delta 2Hallcanes) recovered from the Arctic Ocean show a substantial deuterium (2H)-enrichment at the onset of the CIE which was argued to potentially reflect reduced rainout in the mid-latitudes, resulting in increased precipitation in the Arctic (Pagani et al., 2006). Similar trends observed in n- alkane records during ETM2 from the same location confirm the uniformity of isotopic expression of high-latitude hydrological changes with rapid warming events. A detailed analysis of the timing of shifts in delta 2Hn-alkane and delta 13Cn-alkane at the base of the events indicates changes in high-latitude hydrology occurred prior to the input of 13C-depleted carbon. Potential reasons and implications for carbon sources are discussed. Next, isotope records from two co-located PETM sections in Italy at Forada (Tipple et al., 2012) and Cicogna (this study) are used to evaluate the impact of local processes such as n-alkane transport and integration processes on geological records. While the overall delta 2H trends are similar for both sections, isotopic values are offset by up to ~15%0. Finally, changes in global biomarker records are compiled and evaluated in the context of mean global temperatures and meridional temperature gradient. Using a Rayleigh distillation model, we interpret isotopic changes as pre-CIE change in high-latitude hydrology with a decrease in the meridional temperature gradient, followed by an increase in the meridional temperature gradient during the body of the PETM. |
