Ice-sheet dynamics during late Cenozoic super-warm periods in the Amundsen Sea sector of West Antarctica recorded by variations in ice-rafted debris deposition

• Main Author: Giere, Luca
• Format: Thesis
• Language: unknown
• Published: Department of Geosciences 2022
• Subjects: Amundsen Sea; Antarctic; Misi; Simu; West Antarctic Ice Sheet; West Antarctica; Antarc*; Antarctica; Ice Sheet; Iceberg*
• Online Access: https://epic.awi.de/id/eprint/57342/; https://hdl.handle.net/10013/epic.572502f4-7b22-4bd2-9c27-035387068d09

The West Antarctic Ice Sheet (WAIS) is highly susceptible to melting and eventually collapsing during interglacial periods and since it is mainly based below sea level, external influences such as the ‘Marine Ice Sheet Instability (MISI)’ have a significant impact on its stability. Under currently rapidly changing climate conditions thinning and ice flow acceleration can already be observed, entailing an increased risk of a vast glacial retreat into deep hinterland basins. With certain conditions models already simu-late this but still no decisive geological evidence exists. Therefore, it is necessary to analyze time peri-ods of the geological past, with comparable temperature and CO2 conditions to those expected for coming decades and centuries. In order to reveal dynamics of late Cenozoic super-interglacial periods, cores at two sites were drilled in the Amundsen Sea during IODP Expedition 379 – recovering continu-ous sediments reaching back to the late Miocene. The Amundsen Sea Embayment (ASE) represents one of the most dynamic sectors of West Antarctica and it is suggested that a collapse would likely be initialized here since over deepened glacial troughs extending onto the shelf allowing warm and denser Circumpolar Deep Water (CDW) reaching the grounding line, facilitating the MISI. To identify past major drawdown events, discharge variations of icebergs recorded by the deposition of ice-rafted debris (IRD) have been analyzed from early-mid Pliocene and mid-Pleistocene intervals to clearly identify advances and retreats of the ice sheet. To determine whether those intervals can clearly be attributed to drawdown events, results of IRD discharge and selected existing data from Expedition 379 were combined in a multi-proxy approach. Overall, several intervals were identified in which the combined data clearly indicate interglacial conditions with open-marine conditions, further suggesting partial or full disintegration of marine-based WAIS portions. For the intervals investigated in this thesis, this is ...