Contributions of Glacial Isostatic Adjustment to the Earth's Static Gravity Field and Horizontal Crustal Motions
J.M. Reusen (TU Delft - Planetary Exploration)
L.L.A. Vermeersen – Promotor
W. van der Wal – Promotor
B.C. Root – Copromotor
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Abstract
In the past, the Earth has been subject to various ice sheet growth and melt events. The ice exerts a pressure on the Earth’s surface, depressing the ground below it. Whenever the ice melts, the Earth responds by raising its surface level again. This process is called postglacial rebound. Glacial Isostatic Adjustment (GIA) is considered to be a broader and more general term, namely the solid Earth response to land ice and surface water redistribution following continental ice growth or melt, which thus includes postglacial rebound.
Today, uplift of up to 13mma°1 is recorded around theHudson Bay area inNorthAmerica, due to the last ice sheets that have melted roughly between eighteen and six thousand years ago. Even higher uplift rates of 30 mm a°1 have been recorded in Southeast Alaska as a response to ice melt that only started 250 years ago. Part of the reason why these uplift rates differ is due to the underlying mantle viscosity. Mantle viscosity determines how fast material in the Earth’s mantle is allowed to flow. A high mantle viscosity implies a mantle in which flow is slow, and a low mantle viscosity implies a weak mantle in which flow occurs easily. The viscosity of the mantle below Hudson Bay is expected to be around the global average value of 1021 Pa s, while the mantle viscosity in Southeast Alaska is expected to be a few orders of magnitude lower. GIA research is performed to infer structural parameters such as its mantle viscosity. Moreover, with more knowledge of GIA we are able to more accurately correct measurements for the effect of GIA. The goal of this thesis is to improve the numerical model setups, contributing to these two goals…