Homework #3 Glaciology, GEOL 4888, Spring 2014 Humphrey

We did these questions, with different parameters in class.

1. Let’s look at the deformation velocity expected in the ablation region of Greenland. Assume the ice is approximately a ‘slab glacier’, uniform in all directions. With a coordinate system x-downglacier, and z-down from the surface, what are the symbols for the main (largest) deviatoric stress and the main strain rate in the ice at the base of the glacier?

2. Now to make the discussion specific, let’s look at a region where the ice is 800m thick, with a surface slope of 1 degree. The ice temperature is about -10C. See table below (notice how much A varies with temperature!)

a. Calculate the total expected deformation velocity.

b. Plot, using graph paper or a computer, the velocity profile.

3. What is the effective stress and what is the effective strain rate in the ice at the base of the glacier? (hint, if you find yourself doing extensive calculations, you are answering the question incorrectly)

Table of Values of A(T), s^-1Pa^-3	Temperature (Celsius)
2.4 x 10^-24	0
9.3 x 10^-25	-5
3.5 x 10^-25	-10
1.2 x 10^-25	-20