| Summary: | Most of the mass loss from the Antarctic Ice Sheet (AIS) occurs by dynamic flow of ice from the interior of the ice sheet to the margins, where the ice flows on the ocean, ultimately breaks apart into icebergs, and melts into the ocean. Due to anthropogenic-caused shifts in the climate system, many glaciers in the AIS are accelerating and thus increasing the contribution of the AIS to global sea-level rise. Understanding, and subsequently projecting, the behavior of these Antarctic glaciers is necessary to constrain the impacts that climate shifts will have on the Earth system and on communities around the world. To this end, the essential knowledge needed relates to the physical processes governing the flow and fracture of ice, some of which are unknown and most under-explored. This thesis seeks to illuminate these processes. I take a three-pronged approach to this question: harnessing satellite and field observations, developing theory, and improving ice flow models to represent completely the feedbacks that affect ice flow and fracture. In the first section of this thesis, I develop a novel technique to estimate both the ice-rock interface conditions and ice viscosity from satellite observations simultaneously. When applying this method, I find that ice is less viscous in the regions of glaciers that deform the fastest. In the next section, I consider the mechanisms causing the reduction of ice viscosity. Firstly, I evaluate magnitude of heating by viscous dissipation and show that in many regions of ice streams, shear heating may create temperate zones from which meltwater drains to the bed. Secondly, I find that changes to the ice microstructure likely play a significant role in rates of ice flow and fracture. In the final section, I propose a framework for including these new processes into ice flow models and construct a method for dynamically evaluating these parameters within ice sheet models. As a result of this work, we have a more complete view of the drivers of accelerating ice mass loss and a path ...
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