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Soot Affects Polar Ice

Soot Affects Polar Ice

Far in the frigid north, glaciers rule and temperatures are harsh. It is not the sort of place one would expect pollution to be a problem, but new NASA research reveals that soot is traveling farther north than previously believed. Soot, or black carbon, could have a huge impact on the delicate Arctic environment by speeding up the melting of Arctic ice, altering temperatures and cloud formation, and changing weather patterns.

Black carbon is released into the atmosphere when fossil fuels are not completely burned, either in vehicles, home heating appliances, or when trees and other plants are burned. When large quantities of soot enter the atmosphere, they create a haze that absorbs energy from the Sun, so the temperature of the atmosphere increases. This atmospheric heating can affect weather patterns and cloud formation.

Dorothy Koch and James Hansen, climate scientists at NASA’s Goddard Institute for Space Studies (GISS), modeled the transport of black carbon particles around the world using the GISS general circulation model. The above images show some of their results. The top image shows where black carbon is concentrated in the atmosphere, and thus where surface temperatures and weather patterns might be affected, and the lower image shows where carbon is predicted to settle on the ground.

In the top image, the regions with the most haze—higher optical thickness—are white, while the least-affected areas are blue. As the image shows, Koch and Hansen found that soot in the atmosphere is most concentrated over southern and eastern China, where industry pumps black carbon into the atmosphere, and over central Africa, where fires are widely used for agriculture. Other regions with high concentrations of black carbon include the United States, Central Europe, and India. The model also reveals that instead of being clear of soot, the Arctic is blanketed with black carbon haze. About one-third of the haze, Koch and Hansen say, comes from Asia, one-third comes from fire around the world, and the remaining third comes from the United States, Russia, and Europe.

Soot does not stay in the atmosphere; it falls out in rain or with dust. Koch and Hansen’s research reveals that soot might have a longer range than previously believed, with higher concentrations reaching far into the Arctic. As dark soot falls on the snow and ice of the Arctic, it turns the white, reflective surface into a dark surface that absorbs the Sun’s energy. This extra energy makes the snow melt more quickly.

The lower image shows where the model predicted the black carbon to fall onto the surface. The highest concentrations are again in eastern China, Europe, and the Eastern United States. The model predicts that more soot falls over the eastern Arctic than in parts of the developed world.

For additional information, see “Black and White: Soot on Ice.”

NASA image courtesy Dorothy Koch and James Hansen, NASA GISS