Chile's Cachet Lake In Patagonia Has Drained 11 Times Since 2008; Increased Flood Frequency Likely

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SANTIAGO — In less than 24 hours Lake Cachet II in Chile's southern Patagonia vanished, leaving behind just some large puddles and chunks of ice in the vast lake bed. The lake's water comes from ice melting from the Colonia Glacier, located in the Northern Patagonian ice field, some 2,000 kilometers (1,250 miles) south of the capital, Santiago.

The glacier normally acts as a dam containing the water, but rising temperatures have weakened its wall. Twice this year, on January 27 and March 31, water from the lake bored a tunnel between the rocks and the glacier wall. The result: Lake Cachet II's 200 million cubic liters of water gushed out into the Baker river, tripling its volume in a matter of hours, and emptying the five square kilometer (two square miles) lake bed.

Cachet II has drained 11 times since 2008 -- and with global temperatures climbing, experts believe this will increase in frequency.

"Climate models predict that as temperatures rise, this phenomenon, known as GLOFs (Glacial Lake Outburst Floods), will become more frequent," said glaciologist Gino Casassa from the Center for Scientific Studies (CES).

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1. Glaciers, Dams and Chile's Baker River

http://www.santiagotimes.cl/chile/environment/23882-chiles-glacial-lakes-under-a-deluge

[font face=Serif][font size=5]Glaciers, Dams and Chile's Baker River[/font]

Thursday, 07 June 2012 20:02 | Written by Jimmy Langman

[font size=4]Global warming an imponderable for Endesa's HidroAysén project.[/font]

[font size=3]Four years ago, the Baker River in Aysén Patagonia suddenly tripled in size, causing a virtual river tsunami. In less than 48 hours, roads, bridges and farms were severely damaged and dozens of livestock drowned. Residents were in disbelief. Jonathan Leidich, an American whose company regularly leads tourists on treks up to nearby glaciers, hiked to the Colonia Glacier at the eastern flank of the Northern Patagonian Ice Field and discovered the source of the mysterious flood: Lake Cachet 2 had vanished. This enormous, two-square-mile glacial lake had emptied its 200 million cubic meters of water in just a matter of hours.

What happened? Glaciologists say it was yet another “glacial lake outburst flood,” or GLOF. An increasing rate of melting at the Colonia Glacier swelled the lake so much so that the resulting water pressure gradually forced the creation of a tunnel beneath the surface of the adjacent ice and drained the lake. Since Cachet 2 emptied in 2008, the lake has “disappeared” ten more times.

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Glaciers on the Chilean side of Patagonia account for more than 90 percent of the Patagonian region’s ice fields. Those fields consist of two non-contiguous sheets: the Northern Patagonian Ice Field, which includes Cachet 2, and the Southern Patagonian Ice Field, the world’s third-largest continental ice sheet after those of Antarctica and Greenland.

Data show that since 1995, the rate of thinning has more than doubled. Studies from NASA show that the Patagonian Ice Fields, which extend some 6,600 square miles altogether, account for about 9 percent of annual global sea level change from mountain glaciers.

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