Watching as an icecap shrinks The Quelccaya Ice Cap is a fairly unique feature on the Earth. The ice

Watching as an icecap shrinksThe Quelccaya Ice Cap is a fairly unique feature on the Earth. The icecap, pictured in this image, is a large glaciated area in the Andean mountains of Peru. The location of this icecap is one of the things that make it fascinating; both Peru and this icecap lie quite close to the Equator. The Quelccaya Ice Cap covers 44 square kilometers and sits at latitude of 13° south.Areas this close to the equator are not typically the best places for icecaps, but this one has formed thanks to the Andes Mountains. It sits at an elevation of 5,470 meters (18,600 feet) on average; the altitude is sufficient to allow it to grow, and it turns out; this icecap is the largest glaciated area within the tropics anywhere on Earth.However, as the modern climate warms, this area of the tropics is becoming increasingly unstable. Since 1978, this icecap has lost 20% of its mass. The effects of a changing climate can be seen in these 2 images, taken in 1988 and 2010 by the Landsat 5 satellite. By 2010, the thick snow cover has retreated, as has much of the ice cover at the fringes of the glaciers. In 1988, a small meltwater lake is highlighted at the end of one of the main outflow glaciers, but that lake has expanded by 2010 and is nearly a kilometer long. Furthermore, about 8 new lakes have appeared, most along the southern edges of the icecap.The retreat of this icecap has offered scientists a unique record of its growth. When the icecap last expanded, it overran plants, freezing them and preserving them in the ice. As it melts today, those plants are exposed and the date that they were frozen can be recovered by measuring the abundance of radioactive carbon remaining in them.That measurement was first done on some plants that were exposed from melting in 1988, the year of the upper image. Those plants were found to be 4,800 years old.That measurement was repeated on plants from recently melted ice by researchers from The Ohio State University. The more recently exposed plants were found to be 6,400 years old.Both of those ages imply that the area was cooling and the icecap was expanding at those times. Taken together though, those 2 ages mean…much older ice is melting today than was the case only 25 years ago, and the ice is retreating rapidly.Based on the ages for those 2 sites, the simplest conclusion is that ice which took 1,600 years to grow has melted away in 25 years.-JBBImage Credit: NASA IOTD:http://earthobservatory.nasa.gov/IOTD/view.php?id=80925&src=shareOSU Press release:http://researchnews.osu.edu/archive/icerosetta.htmNew York Times coverage, with highly recommended before and after image of the formation of the large meltwater lake:http://www.nytimes.com/2013/04/05/world/americas/1600-years-of-ice-in-perus-andes-melted-in-25-years-scientists-say.htmlQuelccaya ice Cap (Wikipedia):http://en.wikipedia.org/wiki/Quelccaya_Ice_Cap -- source link

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