Antarctic ice shelf crevasses, damage and deformation – a numerical modelling study

Gerli, Cristina (2023) Antarctic ice shelf crevasses, damage and deformation – a numerical modelling study. Doctoral thesis, Northumbria University.

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Abstract

The ability of ice shelves to modulate upstream grounded ice flow has motivated a wide range of studies analysing the impact of ice-shelf fracturing, damage, and calving on the overall mass balance of the Antarctic Ice Sheet. Despite significant efforts to understand these phenomena, constraining ice sheet models for future sea level rise projections remains a pressing challenge. This thesis comprises three numerical modelling studies, each of which aims to investigate a specific mechanism affecting the structural properties of Antarctic ice shelves. The first study examines the impact of an immediate downward propagation of all pre-existing crevasses on Antarctic ice shelves on the flow of grounded ice. The findings of this work reveal a variable response among the studied ice shelves, reflecting their individual buttressing and confinement capabilities. Although the sensitivity of grounding zone regions remains critical to crevasse propagation, the findings further suggest that despite the extensive fracturing, ice shelves still offer significant buttressing to the upstream ice. The second study of this thesis aims to evaluate the damaged state of major Antarctic ice shelves providing an overview of their current structural integrity. To improve future sea level rise projections, considerable efforts have been focused on using artificial intelligence to track crevasses in remote sensing imagery to inform ice sheet models. Here we further question the relevance of these crevasse maps in the context of current ice dynamics and find a weak relationship between remotely-sensed crevasse maps and physically inferred damage maps. The results of this work indirectly emphasize the limited influence of surface-detected crevasses on current ice dynamics, highlighting the importance of accurately constraining the inferred ice rate factor for future modelling purposes. Since many studies have challenged the legitimacy of the standard parameterisation of the stress exponent n in Glen’s flow law, the third study of this thesis develops a modelling framework to test and calibrate this value with observations. Our study supports, to some extent, the use of n=3 in Glen’s flow law but also challenges the notion of a single, universal value of n. This highlights the importance of further research to examine the spatial variability of this parameter since it would likely enable more accurate projections of future sea level rise and more reliable damage analyses. Overall, the modelling studies that make up this thesis have yielded valuable insights into the role of crevasses and damage in ice dynamics and the challenges associated with accurately capturing these phenomena within modelling frameworks.

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