It's a well-known fact that increasing global temperatures, of both the atmosphere and ocean, are contributing to the melting of glaciers and ice sheets on a global scale. Another contributing factor is the presence of black soot originating from massive population centers. For example, glaciers in the Himalayas, which are in close proximity to heavily industrialized Asian countries such as China, are melting at a faster pace due to the presence of this black soot.
Global Warming and Black Soot
A recent study conducted by NASA scientists aimed to look at how glaciers in the Himalayas were responding to global warming. What they found was that glaciers in the western Tibetan Plateau were melting faster than the global average for melting glaciers. Increases in global temperatures, and temperatures in the region, were not enough to explain these regional phenomena. The culprit, scientists hypothesized, was black carbon, or black soot, in the atmosphere.
Models were used to determine how black soot originating from densely populated south Asian cities could adversely affect the melting rate of Himalayan glaciers. What they found was that wind currents carried this black soot over affected glaciers. The impact was due to two scenarios: first that the black soot was warming the atmosphere over the glaciers more quickly than global warming; and second, that the black soot was falling on the glaciers, causing more radiation absorption.
Black Soot and Solar Radiation Absorption
Solar radiation is absorbed much more easily by dark colored surfaces than by light colored surfaces, which act as a radiation reflector. This is one of the reasons that the scientific community is so alarmed by the melting of glaciers and ice sheets around the globe. Ice sheets and glaciers reflect the sun's radiation, which helps to regulate the temperature of the planet. Less white surfaces on the planet means more radiation is absorbed into our oceans and atmospheres, causing global warming.
In the case of the black soot, the pollution in the atmosphere over the Himalayan glaciers is causing the atmosphere to absorb more solar radiation. This creates a layer of warm air over the Himalayas, which increases glacial melting. The soot also falls out of the atmosphere and leaves a layer of black dust on the glaciers. This increases melting by darkening the glacier and causing it to absorb more radiation rather than reflecting it back into the atmosphere.
From this study, scientists have determined that the presence of black soot in the atmosphere plays just as much of a role in the melting of glaciers as global warming does due to the presence of green house gases. If the release of black soot into the atmosphere continues, Himalayan glaciers may continue to melt at their current rate until they are gone by mid-century.
Source:
Cook-Anderson, G., "New Study Turns Up the Heat on Soot's Role in Himalayan Warming"12/14/2009, Nasa.gov
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Alexandra Matiella Novak - With a PhD in Geology and expertise in science education, Alexandra is passionate about increasing the public's Earth science literacy.
