On the role of Antarctic sea-ice loss in driving swell-induced flexure of ice shelves
Date
2025
Authors
Teder, Nathan
Editors
Advisors
Bennetts, Luke
Massom, Rob (Australian Antarctic Division)
Reid, Phil (Bureau of Meteorology)
Massom, Rob (Australian Antarctic Division)
Reid, Phil (Bureau of Meteorology)
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Thesis
Citation
Statement of Responsibility
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Abstract
This thesis investigates the impact of sea ice losses on increasing ice shelf flexure forced by ocean swell, using satellite imagery for ice shelves and sea ice, a model hindcast for ocean waves, and mathematical modelling for the coupled system. It is motivated by the link between the disintegration of the Larsen B and Wilkins ice shelves and prolonged regional deficits in offshore sea ice. This allowed swell to reach the ice shelf and amplify fractures until the point of large-scale ice shelf calving. The thesis is split into three projects, with the first looking at the seasonality of sea ice-free conditions for ice shelves around Antarctica. An algorithm is developed to determine when an ice shelf has a sea ice-free ocean corridor adjacent to it and to extract wave statistics from areas that could directly reach the ice shelf. The results show that the average corridor season for ice shelves is typically between late-December to mid-April. However, there are large variations between ice shelves due to regional differences influencing sea ice. A consequence of this variability is that some ice shelves, such as the Fimbul, Shackleton, Wilkins, and Ross, record a climatological average of >4 m swell at certain times throughout the year. The second project investigates how swell flexure influenced the large-scale calving events that occurred to Voyeykov Ice Shelf in 2007, and Wilkins Ice Shelf in 2008. A seven-year dataset of the length of the sea ice barrier and swell-induced flexural stresses is calculated for the Wilkins and Voyeykov Ice Shelf fronts. Both ice shelves recorded multiple periods of high accumulated swell-induced flexural stresses in the eighteen months before calving, alongside the coincident loss of consolidated coastal landfast sea ice (fast ice) and build-up of flexure on the ice shelf front. A conceptual model is proposed for how swell flexure preconditions calving, with a discussion on other calving events that potentially fit this model. The third project is on the back-to-back record Antarctic sea ice extent lows in 2022 and 2023, and how they influenced swell-induced flexural stress. A ten-year record of swell flexure was built between 2014–2023 which took into account changes in near-shelf thickness, sea-ice cover ”length” (length of sea ice protecting an ice shelf from incoming swells), and wave statistics for fourteen ice shelves around Antarctica. While 2023 recorded high circumpolar swell flexure, it was below average in 2022, due to relatively weak incoming swell. Further investigation into swell flexure and its potential causes indicates a significant relationship with changes in ice cover and peak period. The impact of future conditions based on enhanced current extremes in sea ice, waves, and ice shelf thickness showed that swell-induced flexure could make a considerable contribution to total stress for most ice shelf fronts if multiple extremes occur simultaneously. This thesis quantifies and interprets how a loss of Antarctic sea ice influences swell-induced flexure on ice shelves by showing the seasonality of incoming swell, alongside how it preconditions large-scale calving, and how swell-induced flexure develops if climatic extremes occur in sea ice.
School/Discipline
School of Computer Science and Mathematics
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Computer Science and Mathematics, 2025
Provenance
This thesis is currently under embargo and not available.