Quelccaya Ice Cap

Quelccaya Ice Cap
Quelccaya Ice Cap on 2010/09/25
Type	Mountain glacier/Icecap
Location	Peru
Coordinates	13°56′0″S 70°50′0″W / 13.93333°S 70.83333°W / -13.93333; -70.83333
Area	44 km2 (17 mi2)
Terminus	Outlet glaciers
Status	Retreating

The Quelccaya Ice Cap is the largest glaciated area in the tropics. Located in the Cordillera Oriental section of the Andes mountains of Peru, the ice cap is at an average altitude of 5,470 meters (17,950 feet) and spans an area of 44 square kilometers (17 square miles). As with the majority of the Earth's glaciers, the Quelccaya Ice cap has retreated significantly since it was first studied. Since 1978 the icecap has lost approximately 20% of its area, and the rate of retreat is increasing.

Comparing pictures taken in 1963 and 1978, an annual retreat rate of 4.7 meters (15 feet) was estimated. In the first few years of the 21st century, the annual retreat was measured to be as much as 205 meters (673 feet), more than 40 times as fast. The major outlet glacier from the Quelccaya Ice Cap, the Qori Kalis Glacier, has also retreated significantly since 1963.

Lonnie Thompson and his research team have drilled ice cores from Quelccaya that date back almost 2,000 years and have used them to study changes in atmospheric conditions over this period. In these samples, the oxygen isotope ratio, oxygen-18 to oxygen-16, has risen abruptly in the last 50 years, an indicator of regional warming. As the ice cap is retreating, it is exposing almost perfectly preserved, unfossilized plant specimens that have been dated to 5,200 years before present, indicating that it has been more than 50 centuries since the ice cap was smaller than it is today.

Ice cores taken from Upper Fremont Glacier in the U.S. state of Wyoming show an oxygen isotope profile similar to that of the Quelccaya ice cores at the end of the Little Ice Age, a period of cooler global temperatures between the years 1550 and 1850. The sudden alterations in the oxygen isotope ratio found in ice core samples from these two glaciers, which are at great distance from each other, provide evidence of a sudden global climate change in the mid-latitude regions of the planet at this time.