Glacial Isostatic Adjustment in a region of complex Earth structure: The case of WAIS

• Main Author: Powell, Evelyn
• Other Authors: Mitrovica, Jerry X, Denolle, Marine, Huybers, Peter, McColl, Kaighin
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Geophysics; Antarctic; The Antarctic; West Antarctica; West Antarctic Ice Sheet; Canada; Antarc*; Antarctica; Ice Sheet
• Online Access: https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37370254

In this thesis, we consider surface loading effects associated with our dynamic cryosphere. Glacial Isostatic Adjustment (GIA) models have been used to constrain the extent of past ice sheets and viscoelastic Earth structure, and to correct geodetic and geological observations for ice age effects. These models, however, often only consider depth-dependent variations in Earth viscosity and lithospheric structure. Seismic, geological, and geodetic evidence indicates the Antarctic Ice Sheet is underlain by complex, high amplitude variability in 3-D viscoelastic structure. In contrast with West Antarctica’s low viscosity mantle, Canada, the location of the former Laurentide Ice Sheet, is underlain by a thick craton and mantle viscosities higher than the global average. GIA modeling with 3-D mantle structure requires greater model specificity and fidelity, but will also provide a deeper understanding of the past and future evolution of the cryosphere. Our investigation is motivated by two questions: How does 3-D Earth structure impact observations of GIA-induced deformation, and how will 3-D Earth structure affect predictions of sea-level change? We compute gravitationally self-consistent uplift, gravity, and sea-level changes and show that 3-D Earth structure will have significant effects on sea-level changes associated with West Antarctic Ice Sheet melt during interglacial periods. Further, we show that Antarctica’s viscoelastic structure will impact geodetic observables even for timescales when the Earth is commonly treated as a purely elastic body. We demonstrate how the bias in crustal deformation induced by this 3-D structure will impact standard methods to use GPS observations to infer viscoelastic structure in West Antarctica. Finally, we use sea-level modeling to estimate the emergence of an island from Canada’s waters in order to corroborate an Indigenous people’s land claim.