From Yale Environment 360 (Jonathan Moens):
Using satellite data, scientists are documenting the inexorable melting of South America’s glaciers and ice fields, with Andean glaciers thinning by nearly three feet a year since 2000. The loss of ice poses a threat to water supplies and agriculture from Bolivia to Chile.
In recent decades, nearby residents of the Cordillera Vilcanota have watched in dismay as the Colquepunco and surrounding glaciers have steadily shrunk. Now, researchers in Germany and France have quantified just how rapidly ice in Peru and throughout the Andes is disappearing. Using high-resolution data generated by satellites and a 2000 Space Shuttle mission to create three-dimensional representations of Andean glacier change over time, the researchers calculated that the area covered by glaciers in Peru shrank by nearly a third from 2000 to 2016…
Across the Andes, glaciers have lost nearly 3 feet in thickness annually since 2000, according to Etienne Berthier, a glaciologist at the Laboratory of Geophysical Studies and Oceanography in Toulouse, France, who recently published his findings in Nature Geoscience. Warming temperatures also have caused glaciers to swiftly recede, particularly in the southern Andes, where some glaciers have retreated 5.5 miles in the past century. Ninety-eight percent of Andean glaciers have shrunk this century.
Glaciers are vital resources for communities in and around the Andes, where meltwater is used for drinking, irrigation, and hydroelectric power — especially in arid regions and during periods of drought. “The disappearance of glaciers will have an impact on the cities, but not just cities — locals, farmers, and people who do agriculture more broadly,” says Francou.
The loss of Andean glaciers also has global repercussions. Nearly all the world’s ice is locked up in the vast ice sheets of Antarctica and Greenland, with lower-latitude mountain glaciers and ice caps making up only 4 percent of the world’s land ice area. But because the world’s mountain glaciers — including in the Andes, the Himalayas, the Tibetan Plateau, the Alps, and various Alaskan and Russian ranges — are melting so rapidly, they have been responsible for a disproportionate share of global sea level rise in recent decades. No mountain region has lost more ice, relative to its size, than the Andes.
Until recently, information regarding the speed and quantity of Andean ice loss was generally restricted to more easily accessible sites, with scientists manually planting stakes in glaciers and recording changes in their mass over the years, says Berthier. But the recent satellite studies have greatly expanded scientists’ ability to track melting glaciers in the Andes and around the globe.
Patagonia’s ice fields account for 83 percent of all ice loss in South America.
“Our study, and the one from Etienne Berthier, are the first studies that cover the whole [South American]continent based on measurements everywhere,” says Thorsten Seehaus, a glaciologist at Friedrich-Alexander-Universität Erlangen-Nürnberg, who recently published his findings in Nature Climate Change.
Berthier and his team were able to obtain data covering most sub-regions of Andean glaciers, giving the researchers a more accurate picture of the pace of glacial retreat and enabling them to better forecast how quickly glaciers will recede in the future.
What the new data shows is that while Andean glaciers overall are receding, they are doing so at varying rates in different regions. In the Desert Andes, for example, a small number of glaciers are actually expanding or holding steady, says Seehaus — though these account for only 1.3 percent of the glaciers studied.
The overall trend, though, is abundantly clear. Andean glaciers — from the small icy regions of Colombia and Venezuela in the north all the way to Patagonia’s glaciated expanses in the south — are rapidly shrinking.
The south Patagonian ice fields are the fastest-melting on the continent, thinning by an average of nearly 3.3 feet a year, according to Berthier’s study. Together with the northern Patagonian ice fields, these regions account for 83 percent of all ice loss in South America. The reason for this, explains Francou, is that the low-altitude glaciers of Patagonia make them particularly vulnerable to rising air temperatures.