Surface mass balance (SMB) captures snow fall, surface melt, water runoff, and other forcings that control the mass balance at the surface of glacier ice.
By perturbing it using an SMB anomaly, we try to understand the reaction of Alaskan glaciers to climate change.
ΔH(m) and ΔV(m/yr) are the thickness and velocity change induced by the surface mass balance (SMB) anomaly.
H(m) and V(m) are the resulting thickness and velocity of the glacier after SMB anomaly.
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Introduction
This simulation of Columbia glacier, Alaska, is the result of work carried out by Dr. Gardner and Dr. Larour on understanding the evolution of this large glacier in the coming decade. The interface allows for perturbations to the surface mass balance (SMB) of the whole glacier.
Surface Mass Balance (SMB)
Surface mass balance (SMB) captures snow fall, surface melt, water runoff, and other forcings that control the mass balance at the surface of glacier ice. By perturbing it, we try to understand the reaction of Alaskan glaciers to climate change. For each perturbation, this simulation computes the impact on stress-balance and mass-transport of the glacier, for a 10 year period. The final output of the simulation is a 10 year movie of the evolution in ice thickness and ice surface velocity of the glacier.
Datasets Used for the Simulation
- Contour for the glacier from Gardner, pers. comm. (Download shape file)
- Surface DEM from 2007 SPOT panchromatic image at a spatial resolution of 40 meters (Korona et al, 2009).
- Bedrock elevation from McNabb et al., 2012.
- Surface Mass Balance: from comprehensive observations of winter accumulation and summer melting over the HAIG glacier, period 2001-2012 (cf. Adhikari and Marshall, TC 2013), and corrected to generate negligible initial thickness changes prior to perturbation.
- Surface velocities from Fahnestock and Gardner, pers. comm., unreleased.
Model Settings
- 3,771 element anisotropic mesh adapted to surface velocities (range of resolution, 10 to 5000 m).
- 10 year long relaxation of the glacier prior to simulation start.
- 10 year long simulation (6-week time step).
- Surface mass balance (SMB) perturbation range: -5 to +5 m/yr (applied the entire time).
- Stress Balance: computed using the Shelfy Stream Approximation (MacAyeal et al., 1993).
- Transient simulation including both stress balance and mass transport.
- Steady-state temperature regime.
- Fixed calving front: no ice/ocean interactions.
- Basal drag: snap-shot inversion using surface velocities (following Larour et al., 2012.
- Results displayed at 1-year time intervals.
How to Run the Simulation
To start the simulation, perturb the mean SMB trend with an anomaly using the slider, then click the 'RUN' button. Results will be computed by the JPL ISSM server, downloaded, and rendered as a movie.
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