Glacial Budgets

AIM: To understand the concept of glacial budgets and the inputs and outputs of glacial material

So now we know what a glacier is and how it is formed - but what we havent covered is where the materials come from!

Sources of glacier ice are:

Direct - From water of the glacier itself.

Indirect - From snow or ice crystals in the atmopshere.

A Glacier can be viewed as a system with inputs, stores, transfers and outputs ( as shown in figure 1) :

 Figure 1: Image illustrating the glacer mass budget showing major mass inputs and ouputs. (Source: Glaciers)

These Include:

• Inputs: precipitation in the form of snow and ice, and avalanches which add snow, ice and debris from the valley side.
• Storage: represented by the glacier itself.
• Transfer (throughput): this is the way ice moves.
• Outputs: This is water vapour from evaporation of water on the ice surface and water in liquid form from ablation (melting). The debris deposited at the snout can also be considered an output.

Glacial Budget:

• The upper part of the glacier is where inputs exceeds outputs = zone of accumulation.
• The lower part is where outputs exceeds inputs = zone of ablation.
• Between the two zones is the line of equilibrium - this seperates net loss from net gain.
• Net Balance = difference between the total accumulation and the total ablation during 1 year.

REFERENCES:

Portland State University (Undated) "Glacier Change in the Upper Skagit River Basin" Available at http://www.glaciers.pdx.edu/Projects/LearnAboutGlaciers/Skagit/Basics00.html#top [Accessed 01/08/2011]

Professor Tweed, F (2011) "Glaciers & Ice Sheets - Formation" Lecture from The Geography Department, Staffordshire University. 

Redfern, D & Skinner, M (2005) Advanced Geography. 2nd Edition. Philip Allan Updates, Oxfordshire