Soot in the arctic snowpack—a cause for perturbations in radiative-transfer. Atmos. Environ
Climate models indicate that the reduction of surface albedo caused by black-carbon contamination of snow contributes to global warming and near-worldwide melting of ice 1,2 . In this study, we generated and characterized pure and black-carbonladen snow in the laboratory and verified that black-carb...
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| Language: | English |
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1985
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1069.906 http://www.ce.berkeley.edu/sites/default/files/assets/users/kirchstetter/Hadley%20and%20Kirchstetter,%20BC%20snow%20albedo%20reduction,%20Nature%20Climate%20Change,%202012.pdf |
| Summary: | Climate models indicate that the reduction of surface albedo caused by black-carbon contamination of snow contributes to global warming and near-worldwide melting of ice 1,2 . In this study, we generated and characterized pure and black-carbonladen snow in the laboratory and verified that black-carbon contamination appreciably reduces snow albedo at levels that have been found in natural settings 1,3,4 . Increasing the size of snow grains in our experiments decreased snow albedo and amplified the radiative perturbation of black carbon, which justifies the aging-related positive feedbacks that are included in climate models. Moreover, our data provide an extensive verification of the snow, ice and aerosol radiation model 1 , which will be included in the next assessment of the Intergovernmental Panel on Climate Change . Snow is among the most reflective of natural surfaces on Earth. Addition of dark impurities decreases its reflectance, also known as albedo, and increases its absorption of solar energy. In 1950s Soviet Central Asia, following a practice dating back to the time of Alexander the Great, snow was intentionally darkened with coal dust to accelerate glacial melting and increase the supply of irrigation water. In contrast, present-day, impurity-enhanced glacial melting that stems from the pollution of snow with trace amounts of black carbon (BC) is unintended and a cause for concern 1,2,6 . BC, a main component of microscopic soot particles produced from the burning of diesel, coal and biomass, strongly absorbs solar radiation. Radiation-transfer calculations indicate that seemingly small amounts of BC in snow, of the order of 10-100 parts per billion by mass (ppb), decrease its albedo by 1-5% (refs 2,7,8). When included in climate models, this BC-induced albedo reduction constitutes a positive radiative climate forcing that contributes to global and regional warming because less solar energy is reflected back to space. The globally averaged radiative forcing from BC contamination of snow is small (0.05 ... |
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