Saturday, November 7, 2009

Cook Ice Cap - Dramatic Melting Raises Concern

By Joan One

The Cook ice cap is the largest French glacier which is located over twelve thousand kilometers from the Alps, on the Kerguelen Islands. In 1963, the Cook ice cap had an area of approximately 500 square kilometers. Glaciologists have observed the increasingly rapid shrinkage of the French glacier using recently collected satellite data.

Over the last four decades, scientists have witnessed the thinning of the Cook ice cap by about 1.5 meters each year. The decrease in the area of the glacier has been at about 20%. The retreat of the glacier has been recorded as being twice as rapid since 1991. This research on the shrinkage of this ice cap has been published in the Journal of Geophysical Research.

The initial studies carried out on the melting of the Cook ice cap showed an initial slow retreat of the Ampere glacier, which is one of the outlet glaciers of the Cook ice cap between 1800 and 1965, which subsequently became much more rapid. In situ monitoring of the French glacier has no longer been carried out since 1974. Nevertheless, observations conducted from space between 1991 and 2006 have allowed scientists to collect data about the French glacier which is located in a fairly inaccessible area.

Glaciologists began their studies of the French glacier by compiling a complete inventory of the glaciers found on the Kerguelen Islands. At the time, these glaciers covered over 700 kilometers square, including the 500 kilometers square occupied by the glacier alone.

Scientists thereafter used Spot and Landsat satellite images to update this inventory for the years of 1991, 2001 and 2003, as well as to quantify the glacial retreat of the Cook ice cap. By 1991, the glacier occupied 448 kilometers square, which area had reduced to 403 kilometers square by 2003. In total, the French glacier has lost 20% of its area in 4 decades, and has been rapidly retreating twice as fast since 1991. Moreover, the scientists were able to estimate the volume loss or mass balance of the glacier over the last 4 decades.

This mass balance gives an accurate characterization of the response of this glacier to climatic variation - temperature and precipitation - and may be used in the comparisons of glacial responses for various regions of the earth. For example, the Cook ice cap has thinned by as much as 300 - 400 meters in glacier tongues at low altitude, while the variations in thickness seem smaller in the higher regions.

Joan One is a freelance journalist and creative writer who immensely enjoys writing and researching into any topic under the Sun.

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