1. GLACIER MODELING Glacial Runoff and Hydrology Modeling Irina Overeem

2. 06 October 20152 Outline OBJECTIVE Learn How to Run GC2D in the CMT Discuss science & technology challenges associated with new process code and coupling. THEORY & EXAMPLE : GC2D ELA, Mass balance and Yosemite LAB 7 Simple Changes to ELA, Mass balance Input Parameters

3. GC2D/Ice Component Task: to calculate glacier evolution. Needs: climate and DEM characteristics Provides: Ice thickness and Melt rate Original Developers: Mark Kessler & Bob Anderson, code was in Matlab; in the CMT tool a simplified version of GC2D is an “Ice” component in the Hydrology project.

4. Mountain Glaciers Valley Glacier Snow-Sourced Delivers sediment & water to pro-glacial river Avalanche-Sourced

5. Glacier Evolution Model Some Theory…….. 1. What is ELA? 2. Basic mechanism of glacier evolution.

6. ELA By definition, the line separating the ablation area of a glacier from the accumulation area is the equilibrium line (Meier, 1962). The net or annual specific balance is zero along this line and its elevation is denoted by ELA. Glacier equilibrium line altitude (ELA) combined with the DEM determines the area of the basin covered with glaciers, and thus area contributing to ice accumulation and ice melt. 60 % of Ag> ELA = zero mass balance

7. Mass Balance From McGregor et al., 2000 Mass Balance = Precipitation – Melt Precipitation === CONSTANT Air Temp === Sine function of a year Ice Flux Calculations: Ud = Ice deformation Us = Basal sliding

8. MODEL SETTINGS Sierra Nevada, California experiments: ELA = 3170 m Mass balance = 0.01 m/yr/m Maximum positive balance = 2 m/yr T ~6deg cooler, P ~ 2X higher Reproduces King Canyon 38 km, Eastern Sierra glaciers about 6 km. GC2D; an Sierra Nevada Example

9. Westward draining glaciers 7 x longer than eastward draining glaciers; topographic asymmetry attributes for most of the length differences (Kessler et al, 2006).

10. Simulation Wiring Note that the component acts without dynamic input of meteorology/snow melt

11. Time Stepping Issues This is almost like a debugging assignment!

12. ELA and Mass Balance Settings Set the number of rivers to two distributary channels. If you can adjust the bedload exponent, the channel with the shortest route to the coast will receive a higher proportion bedload.

13. 06 October 201513 References on GC2D MacGregor, K.R., Anderson, R.S., Anderson, S.P., Waddington, E.D., 2000. Numerical Simulations of Glacial-Valley Longitudinal Profile Evolution. Geology, 28, 11,1031-1034. Kessler, M.A., R.S. Anderson, and G.S. Stock (2006), Modeling topographic and climatic control of east-west asymmetry in Sierra Nevada Glacier length during the Last Glacial Maximum, J. Geophys. Res., 111, F2, F02002, doi:10.1029/2005JF000365. Mark A. Kessler, Robert S. Anderson, Jason P. Briner, 2008. Fjord insertion into continental margins driven by topographic steering of ice. Nature Geoscience 1, 365-369 (11 May 2008) doi:10.1038/ngeo201 Letter

14. 06 October 201514 Theoretical References Cuffey, K.M., Paterson, W.S.B. 2010. The Physics of Glaciers, Fourth Edition Braithwaite, R.J., Muller, F., 1980. On the parameterization of glacier equilibrium line altitude World Glacier Inventory – Proceedings of the Riederalp Workshop, September 1978: IAHS Publ. no. 126, 1980.