Transcript GEOG 5700-Lab 3 Climate-hydrological modeling of

GLACIER MODELING
Glacial Runoff and Hydrology Modeling
Irina Overeem
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
13 April 2015
2
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.
Mountain Glaciers
Snow-Sourced
Avalanche-Sourced
Valley Glacier
Delivers sediment & water
to pro-glacial river
Glacier Evolution Model
Some Theory……..
1. What is ELA?
2. Basic mechanism of glacier
evolution.
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
Mass Balance
Mass Balance = Precipitation – Melt
Precipitation === CONSTANT
Air Temp === Sine function of a year
Ice Flux Calculations:
Ud =
Us =
Ice deformation
Basal sliding
From McGregor et al., 2000
GC2D; an Sierra Nevada Example
•
•
•
•
•
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.
Westward draining glaciers 7 x longer than eastward draining glaciers;
topographic asymmetry attributes for most of the length differences (Kessler et al, 2006).
Simulation Wiring
Note that the component acts without dynamic input of meteorology/snow melt
Time Stepping Issues
This is almost like a debugging assignment!
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.
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
13 April 2015
13
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.
13 April 2015
14