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PostPosted: Sun, 07-08-11, 16:04 GMT 
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Location: Hamburg, Germany
We all know that glaciers are melting at a dramatic speed, which gives rise to a lot of concern worldwide and is usually attributed to global warming.

Since 18 consecutive years (!), my wife and I are spending 3 weeks of summer hiking in the glacier paradise of the Engadin in Switzerland. Here, there are excellent data available for the regress of the glaciers over a large time span of > 100 years. That calls for a more quantitative analysis that I will do in this thread.

Let me focus on the marvellous Moderatsch glacier near Pontresina/Engadin, where we usually are based during our annual hiking vacations. Here is a spectacular view of the Moderatsch glacier as seen from 2500 meter altitude:

Image

About 100 years ago, almost the whole valley was still covered by the glacier, while today you only see a river flowing out from the glacier's mouth. The latter has also shrunk considerably, as this image shows:

Image

What is interesting is that specifically for the Moderatsch glacier, there are signs along the footpath towards the glacier mouth, where the amount of regress in meters since 1900 is inscribed as function of the year. Here is an example:

Image

On average there are such data tables every 10 to 20 years, the first one corresponding to 1900 while the last one to 2010!

With the Maple software it takes only minutes to plot these data and to apply various least-square fits of possible behaviours of the regress with time:

Here is the result:

Image

The red dots denote the amount of observed regress in meters as function of the year. In 1900, the regress was normalized to 0 meters. You see that in 2010 or 110 years later, it is already more than 2000 meters = 2 km! The green curve represents the best fitted linear increase of the regress with time, while the red curve includes a quadratic term as well. It provides a somewhat improved fit to the observations!

Finally, since [length/time] corresponds to a velocity, I plotted the regress velocity in [meters/year] versus time as an equivalent visualization. It looks like this:

Image

In this plot, details become better visible. Clearly, a constant regress velocity is a pretty bad representation of the data. The green fit corresponds to a linearly rising regress velocity, while the red one even includes a quadratic term. You see from the plot that the annual regress speed of the glacier mouth varies between 10..30 meters/year, with a clear tendency to increase with time!

Fridger


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