Printer-friendly version

13 February 2004

Editorial: Snow Country Science

Forrest M. Mims III

Many readers of the E-Bulletin who live in the Northern Hemisphere are in the middle of their snow season. This provides some interesting research opportunities for serious student and citizen scientists. Of special interest is the discovery that even a very light dusting of black carbon particles in the form of soot can significantly enhance the melting of snow and greatly reduce its reflectance.

The atmospheric burden of soot has increased dramatically in recent decades. Coal-burning power plants and biomass fires are among the principle culprits, and both developed and developing countries are pumping huge volumes of soot into the atmosphere.

Soot in snow is warmed by sunlight, and this speeds up the melting of snow. As the soot deposited in the snow melts downward, its concentration increases. The result is that snow contaminated by soot gradually becomes darker.

James Hansen and Larissa Nazarenko of NASA's Goddard Institute for Space Studies have found that the reduction in the reflectance of snow caused by accumulated soot is not considered in models used by researchers to forecast climate change. They believe that soot may be causing earlier springs. Soot might also explain thinning sea ice in the Arctic and the widespread melting of glaciers.

These new findings are as provocative as they are intriguing. Are Hansen and Nazarenko correct? Serious students and citizen scientists might help provide the answer.

To start, fresh snowfall can be examined for microscopic carbon particles by means of a microscope. The number of particles in a known volume of snow melt can be counted. Particles can possibly be photographed on snow. Experiments can be designed to test the melting rate of pristine snow and snow that has been seeded with a known amount of soot. The reflectance of snow containing different concentrations of soot can be measured.

Please contact the E-Bulletin should you pursue these or related ideas. This is a good example of where we can make a contribution to a very new discovery.

Meanwhile, for details about the study by Hansen and Nazarenko, see http://pubs.giss.nasa.gov/abstracts/2004/HansenNazarenko.html
Various NASA and other web sites have articles about the impact of soot on snow. The best way to find these sites is to search on keywords like NASA, soot, snow and temperature.