Deglacial climate and ice sheet evolution of the Ross Embayment, Antarctica

• Main Author: Lowry, Daniel P. (11809511)
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Atmospheric Sciences not elsewhere classified; Geology not elsewhere classified; Oceanography not elsewhere classified; Antarctica; Deglaciation; Paleoclimate; School: School of Geography; Environment and Earth Sciences; 040199 Atmospheric Sciences not elsewhere classified; 040399 Geology not elsewhere classified; 040599 Oceanography not elsewhere classified; 970104 Expanding Knowledge in the Earth Sciences; Degree Discipline: Geology; Degree Level: Doctoral; Degree Name: Doctor of Philosophy; Antarctic; Ross Sea; Antarc*; ice core; Ice Sheet; Ice Shelf
• Online Access: https://doi.org/10.26686/wgtn.17142116.v1

Reconstructing past grounding-line evolution can help inform future sea level projections by constraining marine ice sheet sensitivities to changes in climate. The Ross Embayment, the largest sector of Antarctica, experienced substantial grounding-line retreat since the Last Glacial Maximum. However, different interpretations for the timing and spatial pattern of deglacial grounding-line retreat in this region persist, suggesting either very high or low sensitivity to external forcings. Complicating matters is the sparse paleoclimate record, which is limited spatially and temporally. In this thesis, I address these issues by analysing the output of two transient climate simulations in relation to Antarctic ice core and marine sediment records, and performing and analysing the largest ensemble to date of regional ice sheet model simulations of the last deglaciation in the Ross Sea. The climate models and paleoclimate proxy records exhibit key differences in the timing, magnitude and duration of millennial-scale climate change events through the deglacial period. Using this diverse set of deglacial climate trajectories as ocean and atmosphere forcings, the ice sheet model ensemble produces a wide range of ice sheet responses, supporting the view that external forcings are the main drivers of past grounding-line retreat in the region. The simulations demonstrate that atmospheric conditions early in the deglacial period can enhance or diminish ice sheet sensitivity to rising ocean temperatures, thereby controlling the initial timing and spatial pattern of grounding-line retreat. Through the Holocene, grounding-line position is more sensitive to sub-shelf melt rates as the ocean cavity below the ice shelf expands. Model parameters that control the physical properties of the bed, deformation of the continental shelf, and rheological properties of the ice strongly influence the sensitivity of ice sheets to external forcing. Basin-wide differences in these forcings, driven by oceanic and atmospheric circulation, and spatial heterogeneity of bed properties likely contribute to the asynchronous pattern of retreat in the eastern and western parts of the embayment, as indicated by marine and terrestrial proxy records.