What's in the news?

A news article on the Nature website posted on the 22^nd March 2011 looks at the people living alongside the Colonia River, in the Aysen region of Chilean Patagonia. Their significance is the threat they live under of sudden glacial lake outbursts from the above glacial mountains.

Whilst these lake outbursts are not uncommon globally (see this previous blog post), the region has experienced seven of these events since April 2008. Evidently, this is a much higher rate than seen anywhere else. During each of these seven outbursts, Lake Cachet 2 (of the Colonia glacier), has drained approximately 200 million m³ of water into the Colonia Lake and River in only a few hours. This has created a wave observed as far as 100 km downstream to the Pacific Ocean. The risks to the people of the Colonia River need no further explanation.

The Nature article uses the findings of a paper by Casassa et al. (2010), which has studied the floods to identify a primary cause.  The three year study ultimately found that the main cause was:

“...the repeated opening and closing of a tunnel 8 kilometres beneath the Colonia glacier, connecting Lake Cachet 2 above the glacier and Colonia Lake below it.”

Of course, this alone does not reveal the entire process of glacial lake outburst from the Colonia glacier. As a result, Casassa et al. (2010) found that climate change was the main culprit behind the frequency of these events. This happens as a result of the shrinking and thinning of the glacier in the past few decades, causing a weakening of the natural dam structure that the glacier forms. Thus the water moves between the two lakes with much greater ease. There seems little that can be done about this at present, although the paper offered some hope for the future:

“The researchers conclude that the discharges will continue until the ice has receded or thinned sufficiently to generate a permanent natural drainage channel.”

Figure 1. Ice-laden lake leading up to the Colonia glacier