Glacier surging experiments
Goals of this notebook:

Learn how to set up a surging glacier using OGGM-Edu.
Understand and describe the effects of glacier surging.
In this notebook we are going to explore surging glaciers and how we can experiment with them using OGGM-Edu.

What is a glacier surge?

A small percentage of glaciers undergo short periods of faster flow. They experience a change in morphology and surface characteristics, which sometimes leads to a marked frontal advance. The speed of the ice increases up to 10 - 1000 times of the normal velocity. Record flows are observed with velocities that exceed 100m per day. Surges happen in decadal cycles and can last for 1 up to 15 years.(Jiskoot, 2011)

We start with importing the necessary classes:

Basics
We set up a glacier with a linear bedrock and variable width (see Intro notebook) as a setting for our experiment.

We can then define a surging glacier using the SurgingGlacier class

The surging glacier is essentially the same as a Glacier but with some added attributes, namely the .normal_years , .surging_years and the .basal_sliding_surge. By default these are set to 50 years of non-surging and 5 years of surging, with a basal sliding during a surge 10 times higher then when not surging. These can easily be changed by the user after initialisation.

There are also some changes to how the progression works, and it is not possible to progress a surging glacier to equilibrium.

When we progress this glacier the basal sliding will be increased every 50 years resulting in an increased ice flow.

To learn more about ice flow parameters, take a look at this notebook.

In the plot above we can distinguish the surging periods as a rapid expansion in both length and area (also marked in orange).

Surging glacier experiment
We can compare this to a non-surging glacier. For this we will again employ the glacier collection.

Next we can create a glacier with a stronger surge, add this to the collection and compare it to the two previous glaciers.





from oggm_edu import SurgingGlacier, Glacier, GlacierBed, MassBalance, GlacierCollection



bed = GlacierBed(altitudes=[3400, 3000, 2500, 1500],
                 widths=[500, 400, 300, 300])
mass_balance = MassBalance(ela=2900, gradient=4)

bed.plot()


surging_glacier = SurgingGlacier(bed=bed, mass_balance=mass_balance)


surging_glacier.normal_years

surging_glacier.surging_years

surging_glacier

surging_glacier.basal_sliding

surging_glacier.basal_sliding_surge


surging_glacier.progress_to_year(400)

surging_glacier.plot_history()


surging_glacier.plot()



glacier = Glacier(bed=bed, mass_balance=mass_balance)

collection = GlacierCollection()
collection.add([surging_glacier, glacier])

collection.progress_to_year(400)

collection.plot_history()

collection.plot()

collection



surging_glacier_strong = SurgingGlacier(bed=bed, mass_balance=mass_balance)

surging_glacier_strong.basal_sliding_surge = 5.7e-20 * 50

collection.add(surging_glacier_strong)

collection.progress_to_year(400)

collection

collection.plot_history()






