Applied Math Seminar: The effect of a basal-friction parameterization on grounding-line dynamics in ice-sheet models

Event Type: 
Seminar
Speaker: 
Gunter Lugen
Event Date: 
Monday, February 22, 2016 - 3:30pm
Location: 
SMLC 356
Audience: 
General PublicFaculty/StaffStudentsAlumni/Friends

Event Description: 

The effect of a basal-friction parameterization on grounding-line dynamics in ice-sheet models

 
Abstract:
 
Ice sheets and ice shelves are linked by the transition zone, the region where flow dominated by vertical shear stress makes a transition to flow dominated by extensional stress. Adequate resolution of the transition zone is necessary for numerically accurate ice sheet–ice shelf simulations. The required resolution depends on how the basal physics is parameterized. We propose a new, simple parameterization of the basal hydrology by parameterizing the effective pressure near the grounding line. This parameterization represents connectivity between the basal hydrological system and the ocean in the transition zone. Our model produces a smooth transition between finite basal friction in the ice sheet and zero basal friction in the ice shelf. Combined with an existing friction law linking effective pressure to basal stress and sliding, we show that the knowledge of basal lubrication across the grounding line improves the numerical accuracy of a one-dimensional vertically integrated fixed-grid model. In a set of experiments based on the Marine Ice Sheet Model Intercomparison Project (MISMIP), we show how our one-dimensional model and parameterization respond to variations of parameters driving ice-sheet flow when run to steady state. We further show transient results with time-varying basal stress and ice-shelf melting. Finally, we use the Community Ice Sheet Model (CISM) to demonstrate how our hydrology parameterization impacts three-dimensional models using the MISMIP3D experiment. To this end we compare three different numerical models: the Shallow Shelf Approximation (SSA), a depth-integrated higher-order approximation, and the Blatter-Pattyn model. We reach the same conclusion for both the 1D and 3D models: with our parameterization, a grid resolution of ~1km is sufficient to accurately predict grounding-line dynamics.
 
Tea, Coffee, Cookies and conversation at 3:00pm in the lounge.

Event Contact

Contact Name: Daniel Appelo

Contact Phone: (505) 277-3310

Contact Email: appelo@math.unm.edu