The Hot Zone

World’s Water Towers

Posted by Alison Hawkes on April 13, 2010
Category : Climate Science and Scientists

Apparently it’s not just the polar icecaps breaking apart that’s cause for worry. Yesterday a huge ice block snapped from a mountain in Peru and plunged into a lake, causing a 75-foot tsunami that washed away dozens of homes and a water processing plant in a rural town. Up to a half dozen people died.

Photo courtsey of Times of Malta

Photo courtesy of Times of Malta

So much for slow glacial melt. The Hualcan glacier collapse proves that climate change can be just as dramatic and sudden in the tropics as it is on the poles. This may go down as the first ever inland tsunami. Certainly the mountain villagers weren’t expecting it.

The glacier collapse is also a clear sign that the tropical ice fields are in danger. Peru is home to 70 percent of the world’s tropical ice fields, but there is one notable other: Mount Kilimanjaro in Tanzania.

A 2009 analysis of  Kilimanjaro’s three ice fields ringing the summit by Ohio State University’s Lonnie Thompson showed an 85 percent decline in area covered since 1912, nearly a quarter of it occurring between 2000 and 2007. Their disappearance by 2033 will end an 11,000 year existence on Africa’s highest peak. Fortunately for East Africa, the mountain provides little drinking water, although it does support a thriving tourist industry that may disappear with the ice.

Remnant of Kilimanjaro's eastern ice field, courtsey of Lonnie G. Thompson

Remnant of Kilimanjaro's eastern ice field, courtesy of Lonnie G. Thompson

The Andes are different. Tens of millions of people will be left without drinking water as the ice fields dry up. Called the world’s “water towers,” the glaciers in the Peruvian Andes support the largest tropical ice body. They are the source of hydroelectric power generation, crop irrigation, and drinking water supplies. According to a 2009 World Bank study, Equator’s capital, Quito, draws 50 percent of its water supply from the glacial basin, while Bolivia’s La Paz, 30 percent. Lima, Peru would lose a 10-year supply line of water with the loss of glaciers in its country. Without its icy Andes peaks, South America will surely be for the worse.

Further south from Hualcan near the border with Bolivia is Quelccaya, whose ice cap spans 17 miles but has been rapidly retreating. Lonnie Thompson said half of Quelccaya could disappear this year, exacerbated by natural cycles like El Nino, which releases heat in the lower atmosphere.

The Quelccaya Ice Cap is melting

The Quelccaya Ice Cap is melting

Quelccaya has been studied since 1983, when the first tropical ice cores were taken from its high dome. That has made it a noted case study in climate change. Tropical glaciers like Quelccaya and Kilimanjaro respond strongly  to key climatological variables: temperature, precipitation, cloudiness, humidity, and radiation. That’s according to Thompson’s 2007 paper, Abrupt Climate Changes: Past, Present and Future, published in the Journal of Land Resources and Environmental Law. He wrote:

“.. the observation that virtually all tropical regions are retreating under the current climate regime strongly indicates that a large-scale warming of the Earth system is currently underway.”

In the paper, he notes that recovered ice cores from ice fields in Tibet and the Andes reveal (through analysis of oxygen isotopes) that current warming at high elevations along mid to low latitudes (meaning closer to the equator) “is unprecedented for the last two millennia.” Preserved wetland plants are being exposed by Quelccaya’s glacial retreat and have been radiocarbon dated to more than 5,000 years ago, during the early Holocene when temperatures were warmer.

To put it bluntly, climate change is creating conditions in the Andes last seen more than 5,000 years ago.

–Alison Hawkes

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