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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2017-275
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Development and technical paper
28 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
BrAHMs V1.0: A fast, physically-based subglacial hydrology model for continental-scale application
Mark Kavanagh1 and Lev Tarasov2 1Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John's, NL, Canada
2Dept. of Physics and Physical Oceanography, Memorial University of Newfoundland, St. Johns, NL, Canada
Abstract. We present BrAHMs (BAsal Hydrology Model): a new physically-based basal hydrology model which represents water flow using Darcian flow in the distributed drainage regime and a fast down-gradient solver in the channelized regime. Switching from distributed to channelized drainage occurs when appropriate flow conditions are met. The model is designed for long-term integrations of continental ice sheets. The Darcian flow is simulated with a robust combination of the Heun and leapfrog-trapezoidal predictor-corrector schemes. These numerical schemes are applied to a set of flux-conserving equations cast over a staggered grid with water thickness at the centres and fluxes defined at the interface. Basal conditions (e.g. till thickness, hydraulic conductivity) are parametrized so the model is adaptable to a variety of ice sheets. Given the intended scales, basal water pressure is limited to ice overburden pressure, and dynamic time-stepping is used to ensure that the CFL condition is met for numerical stability.

The model is validated with a synthetic ice sheet geometry and different bed topographies to test basic water flow properties and mass conservation. Synthetic ice sheet tests show that the model behaves as expected with water flowing down-gradient, forming lakes in a potential well or reaching a terminus and exiting the ice sheet. Channel formation occurs periodically over different sections of the ice sheet and, when extensive, display the arborescent configuration expected of Rothlisberger Channels.


Citation: Kavanagh, M. and Tarasov, L.: BrAHMs V1.0: A fast, physically-based subglacial hydrology model for continental-scale application, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-275, in review, 2017.
Mark Kavanagh and Lev Tarasov
Mark Kavanagh and Lev Tarasov
Mark Kavanagh and Lev Tarasov

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Short summary
We present and validate BrAHMs (BAsal Hydrology Model): a new physically-based basal hydrology model which captures the two main types of sub-glacial drainage systems (high-pressure distributed and low pressure channelized). The model is designed for continental glacial cycle scale contexts, for which computational speed is essential. This speed is in part accomplished by numerical methods novel to basal hydrology contexts.
We present and validate BrAHMs (BAsal Hydrology Model): a new physically-based basal hydrology...
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