Lakes Disappearing After Glacial Outburst Floods

100 Places to See in the Americas Before They're Gone cotton coulson / getty images

Two and a half years ago, the Baker River in Chilean 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" six more times.

Such GLOFs don't necessarily arise because of climate change; indeed, some four decades ago a GLOF occurred on the Baker River. But a clear warming trend over the past decade has taken its toll on the world's glaciers, and it is widely agreed that climate change is dramatically increasing the frequency and intensity of GLOFs. Last month, the United Nations Environment Programme (UNEP) released a report on mountain glaciers at the climate-change talks in Cancún, Mexico, stating that glaciers on Argentine and Chilean Patagonia are "losing mass faster and for longer than glaciers in other parts of the world." "Accumulation of science shows us a clear general trend of melting glaciers linked to a warming climate," said UNEP executive director Achim Steiner.

The GLOFs are not just happening at an increasing rate in Patagonia, but worldwide in countries that are home to mountain glaciers. Last April, a huge slab of ice the size of several football fields broke off a mountain glacier and plunged into a central Peru lake creating a tsunami-like wave at least 76 feet high that flooded four towns, destroyed at least 50 homes, and severely damaged a water plant serving a town of 60,000 people. According to NASA's Goddard Institute for Space Studies, this accident came on the heels of the warmest summer season on record in the Southern Hemisphere.

Compared with other countries, Peru is unusually well prepared to cope with sudden lake floods, experts say. The Peruvian Andes mountain chain has witnessed more than 30 glacial floods in the past, killing nearly 6,000 people altogether since 1941. As a result, Peruvian governments have invested millions in working to drain or dam glacial lakes to lessen the hazardous risks. Yet despite significant initiatives to safeguard nearby towns, Lake 513 on the slope of Mount Hualcan burst. Peru is experiencing rapid glacial change. A 2009 World Bank report states that, due to warmer temperatures, Peru's glaciers have declined 22 percent since 1975 and are likely to disappear altogether in two decades, threatening to provoke more floods and eliminating a major source of water and hydropower for its people.

In the Himalayan region of Nepal, China, Bhutan, India, and Pakistan, the International Centre for Integrated Mountain Development has identified 200 "potentially dangerous" glacial lakes. Moreover, scientists predict that several major rivers fed by the Himalayas, such as the storied Ganges River in India, are set to be affected by massive glacial floods in the years ahead and eventually, as the glaciers retreat, the site of serious water shortages for untold millions of people during dry seasons.

At Lake Cachet 2 in Chile, the 36-year-old Leidich says, "The lake is increasing in size, and the floods are getting worse." Especially worrisome to Leidich and other residents is the combined effect these GLOFs may have together with a series of controversial large dams planned for the Baker River as part of a $5 billion HidroAysén project. The companies pushing the project, Italy's Enel and Chile's Colbun, hope to get the first of its Baker River dams readied by 2015. A GLOF-related accident at the dam could wipe out the 512-person Tortel, a small, tranquil village located at the mouth of the Baker River, where the river merges with the Pacific Ocean. Tortel is already issuing GLOF-evacuation orders for its people as the high-water mark of the Baker River hits new peaks with the GLOF events.

Leidich has met with Chilean senators, government ministers, and others to obtain financing for protection measures for ranchers and others living along the Baker. His efforts led to the creation of an early-warning system called the Sentinel Project. High-frequency radios, powered by solar panels and batteries, have been distributed to about 28 families so that they can receive warnings. "This place is a canary in the coal mine for global warming," Leidich says. "If people want to see whether global warming is for real, here it is."

Skeptics of global warming point to some Patagonia glaciers that remain stable, or that are even growing, such as Argentina's Perito Moreno Glacier. But Gino Casassa, director of Glacier and Climate Change Research at the Valdivia, Chile–based Center for Scientific Studies, says that global warming can also lead to more rain, or snow in the case of regions such as Patagonia. Studies from NASA show that the Patagonian Ice Fields, which extend some 6,600 square miles altogether and are the third-largest continental ice sheet in the world, after Antarctica and Greenland, account for about 9 percent of annual global sea-level change from mountain glaciers. "There is scientific evidence showing a new cycle of activity in GLOFs, and not just Lago Cachet. Glaciers are melting and lakes growing in size throughout Patagonia—a clear sign of global warming," says Casassa.

Beyond glacial floods, changing rain patterns linked to climate change and rising seas due to melting glaciers around the globe are also causing major floods. Last year, at a United Nations meeting in New York, Indonesia's Maritime Affairs and Fisheries Ministry said it is considering renting some of its islands to climate-change refugees. Already, many residents of Pacific Island nations are said to be fleeing because of rising sea levels. In the U.S., several recent studies predict that climate-change-related flooding will cause a marked increase in illegal migration from Latin America to the U.S. in coming years.

The official global-warming model of the International Program for Climate Change (IPCC) states that extreme floods are likely to occur more often and with greater intensity. A recent event that fits the IPCC model, climate-change observers say, was the especially long and intense monsoon in August that caused floods leaving an estimated 4 million people homeless in Pakistan. Another example of the global-warming model is India: scientists say data from the past 50 years show that extreme, larger monsoon rains are growing in India while smaller-scale monsoons occur less.

Ghassem Asrar, director of the World Climate Research Programme for the World Meteorological Organization, said that countries must begin to adapt to increasing climate-change floods by building more resilient infrastructure: "Adaptation, managing the risks from extreme events, countries must begin to plan to prepare to deal with the consequences of extreme events." Early-warning systems and other initiatives to adapt to GLOFs are essential facts of life for countries with high mountain glaciers in the decades ahead.

Climate change or not, glacial floods will not wait for a scientific consensus on the matter.