MercoPress. South Atlantic News Agency

Lake disappearance linked to global warming

Experts from Chile's National Forestry Service (CONAF) and the Valdivia Center for Scientific Studies (Cecs) this week linked the May disappearance of a glacial lake in far southern Chile to global warming. The team made these claims after a series of visits to the site of the lost lake starting Thursday, and noted there is a possibility that the lake could reform.

Equipped with state-of-the-art laser scanners, personnel from both organizations measured the depth of neighboring lakes in order to digitally reconstruct the region's topography. The study group wanted to take detailed photographs of lake site itself, speculating that this data would be crucial in determining the cause of the disappearance and whether or not the lake could refill. Dense fog prohibited the team from reaching the site of the lost lake Thursday, but by Monday the weather had improved substantially, allowing the team to make the necessary measurements and conclude that climate change played a major role in what had transpired there. The team believes that the melting of nearby glaciers raised the lake's level to the point where the increased water pressure caused part of a glacier acting as a dam to give way. As glaciers retreat, lakes form behind natural dams of ice or moraine, earth and stones pushed up by a glacier. Those relatively weak dams can be breached suddenly, causing the lake to drain. The advance and retreat of glaciers is part of the normal dynamics of the Patagonia, but the group believes that climate change accelerated the process. "On one side of the Bernardo glacier one can see a large hole or gap, and we believe that's where the water flowed through,'' said Cecs investigator Andres Rivera. ''This confirms that glaciers in the region are retreating and getting thinner.'' Although the team has yet to determine if the hole will prevent the lake from returning to its former size, they concluded that glacier melt is already returning some water to the site. "Water is returning to the lake, but not to the same extent as before the lake disappeared. Smaller amounts of water are returning to the site because we are in the middle of winter and there is very little natural glacier melt at this time," added Rivera. The controversy began in late May when park rangers touring Bernardo O'Higgins National Park in Chile's Region XII were shocked to find that a five-acre glacial lake had completely disappeared. Just two months ago, rangers had seen the 100-foot-deep lake straddling the Témpanos Fjord. Residents of the extremely remote area blame the 6.2 magnitude earthquake which hit the neighboring Aysen region last April and caused over 50 landslides. They suggest that a rift opened up and drained the lake's water. But Chilean glaciologist Gino Casassa, one of the 63 experts who participated in the second UN report on global warming, told the La Tercera newspaper that he believes the lake disappeared due to a relatively common glacial phenomenon: a Glacial Lake Outburst Flood (GLOF). A GLOF is a sudden increase in a lake's volume due to one of various possible causes, including a volcanic eruption, an earthquake, an avalanche, or a portion of a glacier falling into the lake. Casassa speculated that the GLOF broke open a tunnel of ice below the lake, which drained the water to the ocean. "In this zone in particular... we have evidence that, in general, the lakes are filling up as the glaciers melt," said Casassa. Global warming is most likely responsible for this process, as well as for the increase in GLOFs, he added. SOURCE: LA TERCERA, EL MERCURIO, AP By Matt Malinowski (editor@santiagotimes.cl)