The glacier on Mount Pucaranra in the Andes feeds into Lake Palcacocha. A large avalanche would be similar to dropping a bowling ball in a bathtub. Modeling scenarios predict a 100-foot wave so powerful it would blow out the dam. Three billion gallons of ice water would go roaring down the mountain toward the city of Huaraz, burying its 200,000 residents under an Andean tsunami of mud, trees, and boulders. Photo: Jabin Botsford

By Nick Miroff 
7 August 2017

LAKE PALCACOCHA, Peru (The Washington Post) – After a day of bright sunshine, a chunk of ice the size of a dump truck broke off the glacier on Mount Pucaranra a few weeks ago. It plunged into the lake below and kicked up a wave nine feet high.

Victor Morales, a small, catlike man with a tattered ski cap who is the lake’s solitary watchman, scrambled up to a stone hut on the side of the mountain and got on the radio. The wave had damaged an emergency drainage system meant to reduce the volume of the lake. But to his great relief, the earthen dam holding back the water was intact.

“It wasn’t a big avalanche,” Morales said.

Lake Palcacocha is a mile long and 250 feet deep, and the effect of a large avalanche would be similar to dropping a bowling ball in a bathtub. Modeling scenarios predict a 100-foot wave so powerful it would blow out the dam. Three billion gallons of ice water would go roaring down the mountain toward the city of Huaraz, burying its 200,000 residents under an Andean tsunami of mud, trees, and boulders.

Lake Palcacocha is an example of the immediate threats Peru and other developing countries are facing from climate change. The country is especially vulnerable since it is home to 70 percent of the world’s “tropical glaciers” — small, high-altitude ice caps found at the earth’s middle latitudes. Their disappearance has made Peru something of a laboratory for human adaptation to climate change.

So far, it’s not going very well.

“For countries like Peru that are trying to climb out of poverty, there are major social, cultural and economic obstacles to adaptation,” said Nelson Santillán, a researcher at Peru’s national water authority. “Identifying risks is one thing, but doing something about them is another.”

In the weeks since President Trump announced the United States would renege on its commitment to the Paris climate accord, scientists have pointed to new signs the planet is edging closer to a precipice. Maximum temperature records continue falling. New cracks are opening at the polar ice caps.

Peru’s high-altitude glaciers are tiny by comparison, but millions of people depend on their runoff for water, food and hydroelectricity.

Some of Peru’s glaciers have lost more than 90 percent of their mass. While much of the water trickles harmlessly down the mountainside, in places like Lake Palcacocha, it is pooling in great big puddles of melted ice. Many of these new lakes are held back by glacial moraines, which are essentially mounds of compressed sediments. They may be structurally weak, and as the volume of water pushing on them increases, some will collapse.

“We have glaciers across 19 — no, 18 — mountain ranges,” said Marco Zapata, a top scientist at Peru’s institute for glacier research, correcting himself to reflect the latest monitoring data.

“They’re all shrinking.” [more]

A flood of problems

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