| Autor: |
Crawford, Anna1,2 (AUTHOR) anna.crawford@ed.ac.uk, Åström, Jan3 (AUTHOR), Benn, Douglas I.4 (AUTHOR), Luckman, Adrian5 (AUTHOR), Gladstone, Rupert6 (AUTHOR), Zwinger, Thomas3 (AUTHOR), Robertsén, Fredrik3 (AUTHOR), Bevan, Suzanne5 (AUTHOR) |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Earth Surface. Oct2024, Vol. 129 Issue 10, p1-18. 18p. |
| Abstrakt: |
The western region of the wide Thwaites Glacier terminus is characterized by a near‐vertical calving front. The grounding line at this western calving front (WCF) rests on a relatively high ridge, behind which exists a reverse‐sloping bed; retreat of the grounding line into this over‐deepening basin could therefore expose deep calving faces that may be subject to ice‐cliff failure. Here, we use the 3D Helsinki Discrete Element Model to identify the factors that control the calving dynamics in this location. We then focus on the ability of mélange to influence these dynamics given the wide embayment in which Thwaites Glacier terminates. We find that calving along the WCF is currently influenced by ice flow across the grounding line and consequent longitudinal tensile stress and rift formation. Calving is slowed in simulations that are initiated with a highly constricted mélange, with a thicker mélange suppressing calving entirely. We liken the constrained simulations to a scenario in which mélange piles behind a large grounded iceberg. In a future which may see calving become a more dominant control on the retreat of Thwaites Glacier, this type of blockage will be necessary for robust force chains to develop and transmit resistive forces to the terminus. The ability of the mélange to hinder calving at this location will be determined by the presence and rigidity of binding land‐fast sea ice and iceberg keel depths. Therefore, it is necessary to represent calving, mélange and sea ice in a single framework to predict the fate of Thwaites Glacier. Plain Language Summary: Thwaites Glacier, a major outlet glacier of the West Antarctic Ice Sheet, may be vulnerable to rapid retreat. The terminus of Thwaites Glacier is over 100 km wide; in this paper, we focus on the western terminus region, which meets the Amundsen Sea at a near‐vertical ice face. We use a 3D glacier model that simulates ice fracture to identify the factors controlling iceberg calving. We also run simulations to explore the potential for mélange, a conglomerate of variably sized ice pieces in front of a glacier, to impact calving dynamics at this location. Our simulations show that iceberg calving currently occurs through the growth of short ice‐shelf extensions and the loss of resisting forces as the ice begins to float. Our simulations also demonstrate that calving is slowed when a thick immobile mélange is present. The ability of the mélange to apply a backforce to glaciers has been previously identified as an important brake on such calving‐driven retreat. In a future that may see calving become a more dominant control on the retreat of Thwaites Glacier, this type of blockage will be necessary for the transmission of resistive forces to the terminus. Key Points: Calving at Thwaites Glacier's western terminus is controlled by longitudinal tensile stresses and fracturing as basal traction is lost3D modeling demonstrates that mélange, if constrained, can inhibit calving at this locationFuture sea‐ice conditions and iceberg morphology will determine if mélange can compact and transmit substantial resistive forces [ABSTRACT FROM AUTHOR] |
| Databáze: |
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