|Lucia Glacier, Southern Patagonia Icefield. The denuded flanks of the glaciers are another illustration of the rapid retreat of glaciers in this region. Image credit: Andres Rivera.|
Scientists have long known that most of Patagonia's glaciers have been retreating for the past half-century or more. Until recently, scientific studies of this region were limited to ground and aircraft studies of a few glaciers. With the flight of the joint NASA/National Imagery and Mapping Agency Shuttle Radar Topography Mission aboard Space Shuttle Endeavour in February 2000, scientists found themselves with a new tool to conduct a complete study of this entire 17,200 square kilometer (6,641 square mile) region. Now, a joint research effort by NASA and Chile's Centro de Estudios Cientificos has measured the changes in mass in these vast icefields over a 25-year period. This undertaking used data from the Shuttle mission and conventional topographic data from the 1970s and 1990s. Using this unique "big picture" vantage point of space from NASA, scientists took a complete stock of Earth's cryospheric refrigerator in Patagonia. And what the scientists found was that the icebox is defrosting, quickly.
|This animation depicts the thinning of Jorge Montt Glacier
in the northern part of the Southern Patagonia Icefield, South America
between 1975 and 2000. It was created using data from NASA's Shuttle Radar Topography
Mission and the Landsat Thematic Mapper. Animation credit: Vince Realmuto and Zareh Gorjian, Digital Image Animation Laboratory, JPL.
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So what's causing the increased Patagonia thinning? Rignot and his colleagues concluded the answer is climate change, as evidenced by increased air temperatures and decreased precipitation over time. Still, those factors alone are not sufficient to explain the rapid thinning. The rest of the story appears to lie primarily in the unique dynamic response of the region's glaciers to climate change.
"The Patagonia Icefields are dominated by so-called 'calving' glaciers," Rignot said. "Such glaciers spawn icebergs into the ocean or lakes and have different dynamics from glaciers that end on land and melt at their front ends. Calving glaciers are more sensitive to climate change once pushed out of equilibrium."
| Steep glaciers can be seen
running down Mt. San Valentin, the summit of the Northern Patagonia Icefield.
The glacial retreat has already cut the direct supply of ice from smaller
glaciers. Image credit: Andres Rivera
Information about the Shuttle Radar Topography Mission is available at: http://www.jpl.nasa.gov/srtm/. Information on NASA's Cryospheric Science program is available at: http://oceans.nasa.gov/csp/index.html.