April 15, 2013

Glaciers melting 20 years early

Glacial melt in the tropical Andes has already peaked and is in decline.


According to a recent study, water supplied by the glaciers of the Cordillera Blanca in northwest Peru is decreasing due to climate change at least 20 years sooner than expected, according to a new study.

The snow-topped peaks in northern Peru are retreating so much that visitors now come to see how much the glaciers have melted and it is even called climate change tourism by some. Such a fundamental environmental change is expected to have serious impacts. The coastal towns are mostly dependent on glacial melt water and, in Peru’s Amazon rivers – the lifeblood of the rainforest – also depend to a large extent on glacial flows during the dry season (May to September). Rivers have been significantly lower in terms of flow and volume of water during dry seasons over the last ten years.

“Our study reveals that the glaciers feeding the Río Santa watershed are now too small to maintain past water flows. There will be less water, as much as 30 percent less during the dry season,” said Baraer, lead author of the study “Glacier Recession and Water Resources in Peru’s Cordillera Blanca”, published in the Journal of Glaciology.

Shrinking glaciers generate “a transitory increase in runoff as they lose mass,” but the water flowing from a glacier eventually hits a plateau and from then on there is a decrease in the discharge of melt water. This decline is permanent and according to the French Institute for Research and Development , tropical glaciers of the Andes are in rapid decline, losing 30 to 50 percent of their ice in the last 30 years.

Historically, glacial retreat is extremely slow – just one or two km per century. However, the Jorge Montt Glacier in the vast Patagonian Ice Fields receded one entire km in just one year.

In many High Andean tropical and subtropical valleys, spring and summer snow and glacier melt are critical for crops, livestock and human consumption. Several major Andean cities rely heavily on glacier and snow melt for their water supply, such as La Paz and Lima, with demand increasingly outstripping the supply, according to a 2010 IAI communiqué.

The Cordillera Blanca has the most glaciers of any tropical mountain range in the world. In the 1930s glaciers covered up to 850 sq km of the region and now they cover less than 600 sq km. Until recently it was believed that such declines would take place 20 to 30 years from now, allowing time to adapt to a future with less water. “Those years don’t exist,” said Baraer.

In response to these problems, an initiative to collect moisture from the thick sea mist around Lima represents an inventive, cost-effective solution to the ever-expanding Peruvian capital’s shortage of water. Sandwiched between the cool ocean currents of the Pacific Ocean and the Andes, Peru’s coastal capital is a meteorological anomaly – second-largest desert city after Cairo, but with a cooler climate and less than 4cm annually, yet humidity can reach 98%. Home to a third of Peruvians, nearly 9 million people,

Lima is dependent on three rivers that flow from glaciers in the Andes.

Sources: Tierra America


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