15 Mar 2023
 | 15 Mar 2023
Status: this preprint is currently under review for the journal TC.

Basal conditions of Denman Glacier from glacier hydrology and ice dynamics modeling

Koi McArthur, Felicity S. McCormack, and Christine F. Dow

Abstract. Basal sliding in Antarctic glaciers is often modeled using a friction law that relates basal shear stresses to the effective pressure. As few ice sheet models are dynamically coupled to subglacial hydrology models, variability in subglacial hydrology associated with the effective pressure is often implicitly captured in the friction coefficient – an unknown parameter in the friction law. We investigate the impact of using effective pressures calculated from the Glacier Drainage System (GlaDS) model on friction coefficients calculated using inverse methods in the Ice-sheet and Sea-level System Model (ISSM) at Denman Glacier, East Antarctica, for the Schoof and Budd friction laws. For the Schoof friction law, a positive correlation emerges between the GlaDS effective pressure and friction coefficient in regions of fast ice flow. Using GlaDS effective pressures generally leads to smoother friction coefficients and basal shear stresses, and smaller differences between the simulated and observed velocities, compared with using an effective pressure equal to the ice overburden pressure plus the gravitational potential energy of the water. Compared with the Budd law, the Schoof law offers improved capabilities in capturing the spatial variations associated with known physics of the subglacial hydrology. Our results indicate that ice sheet model representation of basal sliding is more realistic when using direct outputs from a subglacial hydrology model, demonstrating the importance of coupling between ice sheet and subglacial hydrological systems. However, using our outputs we have also developed an empirical parameterization that improves application of the Schoof law without requiring explicit hydrological modeling.

Koi McArthur et al.

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Koi McArthur et al.

Data sets

Topography from Bedmachine v2 Mathieu Morlighem, Eric Rignot, Tobias Binder, Donald Blankenship, Reinhard Drews, Graeme Eagles, Olaf Eisen, Fausto Ferraccioli, René Forsberg, Peter Fretwell, Vikram Goel, Jamin S. Greenbaum, Hilmar Gudmundsson, Jingxue Guo, Veit Helm, Coen Hofstede, Ian Howat, Angelika Humbert, Wilfried Jokat, Nanna B. Karlsson, Won Sang Lee, Kenichi Matsuoka, Romain Millan, Jeremie Mouginot, John Paden, Frank Pattyn, Jason Roberts, Sebastian Rosier, Antonia Ruppel, Helene Seroussi, Emma C. Smith, Daniel Steinhage, Bo Sun, Michiel R. van den Broeke, Tas D. van Ommen, Melchior van Wessem, and Duncan A. Young

Surface speed from MEaSUREs E. Rignot, J. Mouginot, and B. Scheuchl

Model code and software

Ice-Sheet and Sea-Level System Model (ISSM) code Mathieu Morlighem, Hélène Seroussi, Éric Larour, Nicole Schlegel, Chris Borstad, Basile de Fleurian, Surendra Adhikari, Johannes Bondzio, Aleah Sommers, Felicity McCormack, and Thiago Dias dos Santos

Koi McArthur et al.


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Short summary
Using subglacial hydrology model outputs for Denman Glacier, East Antarctica we investigated the effects of various friction laws and effective pressure inputs on ice dynamics modeling over the same glacier. The Schoof friction law outperformed the Budd friction law and effective pressure outputs from the hydrology model outperformed a typically prescribed effective pressure. We propose an empirical prescription of effective pressure to be used in the absence of hydrology model outputs.