Investigating Terrestrial-Marine Climate and Carbon Cycle Connections During the Late Miocene and Pliocene: Examples from the Andes and the Northeastern Tibetan Plateau

Abstract

Climate change poses a continuous threat to people, biodiversity and ecosystem stability across the globe. Adaptation and mitigation efforts rely on climate models to accurately predict the magnitude of future climate change. Yet, there remain considerable uncertainties with respect to how the Earth system will respond and operate under elevated CO2 scenarios. The paleoclimate record provides an opportunity to investigate the drivers of climate and environmental change during past periods of global warmth, that can be used to inform and guide models operating under warm, elevated CO2 scenarios. This dissertation consists of three manuscripts focused on resolving climate and carbon cycle dynamics operating in remote, high-elevation regions during the late Miocene and early Pliocene, when global temperatures and atmospheric CO2 concentrations were at levels analogous to near-future climate projections. In Appendix A, I utilize lacustrine carbonate geochemical methods (δ18O and δ13C and Δ47-temperature) to investigate the hydroclimate response to global warming across the Miocene-Pliocene boundary, in the Central Altiplano of the Andes. Detrital and igneous zircon U-Pb geochronology is also presented to refine the age model of this lacustrine sequence. In Appendix B, I present a high-resolution record of hydroclimate and carbon cycle variability (δ18O and δ13C) from lacustrine carbonates of the northeastern Tibetan Plateau, spanning the late Miocene. I compare orbital-scale variability in this lacustrine carbonate δ13C record, to marine δ13C records in the South China Sea, to identify a similar obliquity forcing of the terrestrial and marine carbon cycles. Finally, in Appendix C, I utilize a simple ocean box model approach to explore the potential for the North Pacific Ocean to have acted as a sink for atmospheric CO2 during the late Miocene, under a range of North Pacific Ocean productivity and circulation scenarios. I consider processes that may have facilitated a transport of nutrients to the North Pacific Ocean during the late Miocene, given the climate, environment and tectonic shifts occurring within Asia over this timeframe. Altogether, this dissertation provides valuable new insights into the hydroclimate and environmental response of high-elevation regions to global climate change, and highlights the potential implications of such change, for the global carbon cycle.