Improved basal drag of the West Antarctic Ice Sheet from L-curve analysis of inverse models utilizing subglacial hydrology simulations
<p>The West Antarctic Ice Sheet (WAIS) is the focus of current research due to its susceptibility to collapse, which could potentially contribute to rising sea levels. To accurately predict future glacier evolution, precise ice sheet models are essential. The ice discharge of outlet glaciers i...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/19/2133/2025/tc-19-2133-2025.pdf |
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| Summary: | <p>The West Antarctic Ice Sheet (WAIS) is the focus of current research due to its susceptibility to collapse, which could potentially contribute to rising sea levels. To accurately predict future glacier evolution, precise ice sheet models are essential. The ice discharge of outlet glaciers into the ocean is one key factor here, primarily caused by the basal sliding of ice. Since we cannot directly measure basal properties on a large scale, inverse models can be used to infer the basal drag coefficient by minimizing a cost function that depends on a velocity misfit and a regularization term.</p>
<p>We conduct various basal drag inversions to obtain an improved basal drag distribution for the WAIS. Additionally, we perform L-curve analyses to determine the optimal trade-off between the cost function terms that result in smooth L-curves. The domain L-curve is divided into eight subdomains of the study area to assess how well the inverse method performs in different glaciological settings. Pine Island Glacier exhibits the smoothest L-curves, while slow-flowing regions such as Roosevelt Island reveal rather poorly shaped L-curve behavior for the basal drag inversion. This highlights the importance of performing a subdomain L-curve analysis for large-scale inversions to discover potential problematic regions and to establish suitable regularization for different physical conditions.</p>
<p>Comprehensive basal drag inversion experiments allow us to test the dependence of both the L-curves and the basal drag results on the nonlinearity of sliding and the inclusion of subglacial effective pressure in the friction law. The analysis suggests that nonlinear friction laws are preferable to linear sliding because of reduced variance in the overall inferred friction coefficient and steeper L-curves leading to a more well-defined corner region. We show that a Budd-type friction law that incorporates effective pressure from a subglacial hydrology model rather than a simple geometry-based approximation achieves improved performance in our inverse model in terms of the total model variance ratio, along with faster convergence and smoother L-curves. Further comparison reveals that the basal drag coefficient field has a less variable spatial structure when an effective pressure from the hydrology model is used instead of a parameterized effective pressure, allowing us to interpret the inverted drag coefficient more precisely in terms of the basal properties rather than the basal hydrology.</p> |
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| ISSN: | 1994-0416 1994-0424 |