North Atlantic Climate and Cryosphere Variability Over the Past 20,000 Years

• Main Author: Sinclair, Gaylen
• Other Authors: Kirby, Eric, College of Earth, Ocean, and Atmospheric Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Climate change; East Greenland; glacier; Greenland; Ice Sheet; North Atlantic
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1r66j642h

Reconstructing the sensitivity of past climate to forcings, and of ancient glaciers and ice sheets to this climate, can allow us to better understand the range of climate and cryosphere behavior we may see in the coming centuries. The Arctic is a region of particular importance due to its well-documented amplification of climate change, the presence of the Greenland Ice Sheet, and the acceleration of climate and cryosphere change in the past two decades. In this dissertation, I investigate the past 20,000 years in the area, focusing specifically on the last deglacial period and the late Holocene to answer the overarching question: what magnitude of forcing is required to exceed regional variability in the climate system? I address this through three sub-questions: (1) was there regional variability in retreat of the Greenland Ice Sheet during the last deglaciation, and if so what drove this variability? (2) does Arctic regional climate match the average climate history of the region during the Common Era, and (3) is ice sheet and glacier behavior in southernmost Greenland during the late Holocene synchronous across different glacier types? I use a combination of geostatistical and geochemical techniques to answer these questions, and throughout stress the power of large datasets to reveal significant climate signal within proxy noise. To answer the first question, I present a database of all surface exposure ages and radiocarbon ages published for Greenland. I recalculate all ages using consistent production rates and scaling schemes to allow all ages to be directly compared with each other and to ice sheet models. Factor analysis of surface exposure ages reveals diachronous retreat of the ice sheet, with east Greenland deglaciating during and immediately following the end of the Younger Dryas cold period (~12.9-11.7 ka), with peaks in retreat ~13.0-11.5 ka. In contrast, terrestrial retreat of south Greenland occurs between 11.0 and 10.0 ka, and west Greenland retreats between 10.5 and 7.5 ka. This spatial ...