Ocean Forcing of Quaternary East Antarctic Ice Sheet Evolution: An Ice-Proximal Sedimentary Perspective

• Main Author: Guitard, Michelle E.
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Digital Commons @ University of South Florida 2015
• Subjects: Antarctica; paleoceanography; Quaternary; sediments; Climate; Geochemistry; Geology; Antarctic; Southern Ocean; The Antarctic; Antarctic Peninsula; West Antarctica; East Antarctic Ice Sheet; Pacific; Antarc*; Ice Sheet
• Online Access: https://digitalcommons.usf.edu/etd/9584; https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=10781&context=etd

Antarctica and the Southern Ocean play a critical role in Earth’s climate system. Antarctica’s ice sheets contain enough ice to raise global sea level by ~58 m, and the Southern Ocean distributes climate signals and nutrients to the major ocean basins and the deep ocean. Antarctica’s largest ice sheet, the East Antarctic Ice Sheet (EAIS), was considered stable compared to those in West Antarctica and the Antarctic Peninsula because it was thought to be grounded above sea level. However, subglacial topography now reveals vast submarine basins and measurements of ice velocity in the Pacific sector indicate marine-terminating outlet glacier thinning and retreat over the last four decades associated with warm ocean water presence at depth in some locations over East Antarctica’s continental shelves. Modern observations provide the impetus for investigating past EAIS response to climate change, particularly to ocean thermal forcing. To understand past EAIS response to ocean thermal forcing, marine geologic investigations of sediments recovered from Antarctica’s continental shelves and the Southern Ocean are required, particularly from intervals of warmer-than-modern conditions. This dissertation explores the Quaternary (last 2.6 Ma) behavior of the EAIS by reconstructing outlet glacier behavior using well-dated millennial- to orbital-resolution sedimentary sequences collected from East Antarctica’s continental shelves and the Southern Ocean. Each chapter targets a specific time period, focusing on past warm periods and climate transitions. To establish the timing of glacial advance and retreat, and to reconstruct depositional environment and upper ocean temperature, I utilize the Ramped PyrOx (RPO) technique and radiocarbon (14C) analyses, sedimentary beryllium-10 concentration, and the TetraEther IndeX of 86 carbons (TEX86) paleothermometer. Results yield new insights into the Quaternary evolution of East Antarctica’s marine-terminating glaciers and the role of ocean heat in that evolution. Chapter two investigates ...