The Quelccaya Ice Cap in Peru has been fluctuating in size over the past several decades. Now, scientists believe they know the cause of this phenomenon.
Measurements point to temperature, and not snowfall, as the primary mechanism driving the size of the ice mass.
Justin Stroup and Meredith Kelly of Dartmouth College in New Hampshire carried out the study. In order to test how the glacier has changed with time, the team combined field mapping and examinations of ice cores with beryllium-10 dating. The ice cores were collected by Lonnie Thompson from Ohio State University. This was the first time the geological record of a glacier has been compared directly to an annually-dated ice core.
The Quelccaya Ice Cap in Peru is the largest ice mass in the tropics. It is found 18,000 feet above sea level. Beryllium-10 was used to trace the location of glacier sediments called moraines that accompanied the outlet glacier Qori Kalis. Thomson has tracked the glacier since the early 1960's, and has found the glacier reached its greatest extent 520 years ago. Rising temperatures are thought to be the primary reason the glacier has receded.
"This is an important result since there has been debate about the causes of recent tropical glacial recession - for example, whether it is due to temperature, precipitation, humidity, solar irradiance or other factors. This result agrees with Professor Thompson's earlier suggestions that these tropical glaciers are shrinking very rapidly today because of a warming climate," Kelly said.
Over the last 1,000 years, the Earth has experienced a "little ice age." Geologists are not sure what caused the event, or the extent of cooler temperatures. The warmer temperatures were recorded in other glaciers around the world.
"[G]lacial retreat between [about 520 years ago] coincides with the highest net accumulation values of the 1800 year-long ice core record. Therefore, we suggest that temperature, rather than net accumulation, was the primary driver of these glacial fluctuations. Comparison of the late Holocene fluctuations of Qori Kalis glacier with glaciers in the southern tropical Andes, Patagonian Andes, Switzerland, Alaska, and New Zealand suggests globally synchronous, centennial-scale cold events," the team wrote in their study.
According to the World Glacier Monitoring Service, nine mountain ranges, located in different regions, experienced an average loss of 24 inches of water during the winter of 2011 to 2012.
This new study may help environmental scientists better predict the effects of global warming, especially on glaciers. The details of the study were published in the journal Geology.
