London: Some of the Himalayan glaciers are advancing thanks to the presence of debris such as pebbles, rocks, and debris from surrounding mountains, suggests a new study.
Bodo Bookhagen, of the Department of Geography at UC Santa Barbara, co-authored a paper said, "With the aid of new remote-sensing methods and satellite images, we identified debris coverage to be an important contributor to glacial advance and retreat behaviors.
"This parameter has been almost completely neglected in previous Himalayan and other mountainous region studies, although its impact has been known for some time," he said.
The finding is one more element in a worldwide political controversy involving global warming.
"Controversy about the current state and future evolution of Himalayan glaciers has been stirred up by erroneous reports by the Intergovernmental Panel on Climate Change (IPCC)," stated the study.
"There is no ``stereotypical`` Himalayan glacier. This is in clear contrast to the IPCC reports that lumps all Himalayan glaciers together," said Bookhagen.
Bookhagen noted that glaciers in the Karakoram region of Northwestern Himalayas are mostly stagnating.
However, glaciers in the Western, Central, and Eastern Himalayas are retreating, with the highest retreat rates-approximately 8 meters per year-in the Western Himalayan Mountains.
The authors found that half of the studied glaciers in the Karakoram region are stable or advancing, whereas about two-thirds are in retreat elsewhere throughout High Asia.
Bookhagen explained the difference between debris and coverage by soot and dust on glaciers.
"The debris cover has the opposite effect of soot and dust on glaciers. Debris coverage thickness above 2 centimeters, or about a half an inch, ``shields`` the glacier and prevents melting. This is the case for many Himalayan glaciers that are surrounded by towering mountains that almost continuously shed pebbles, debris, and rocks onto the glacier."
Thus, glaciers in the steep Himalayas are not only affected by temperature and precipitation, but also by debris coverage, and have no uniform and less predictable response, explained the authors. The debris coverage may be one of the missing links to creating a more coherent picture of glacial behavior throughout all mountains.
The findings were reported in the journal Nature Geoscience.