HR: 0800h
AN: A11B-0052    [Abstracts]
TI: Influence of Snowpack Metamorphism on Tropospheric Chemistry
AU: * Taillandier, A
EM: tailland@lgge.obs.ujf-grenoble.fr
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320 United States
AU: * Taillandier, A
EM: tailland@lgge.obs.ujf-grenoble.fr
AF: International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Drive, P.O. Box 757340, Fairbanks, AK 99775-7340 United States
AU: * Taillandier, A
EM: tailland@lgge.obs.ujf-grenoble.fr
AF: CNRS, Glaciology Laboratory, 54, rue Moliere, B.P. 96, Saint-Martin d'Heres, 38402 France
AU: Alvarez-Aviles, L
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320 United States
AU: Alvarez-Aviles, L
AF: Department of Chemistry, University of Alaska Fairbanks, 900 Yukon Drive, Fairbanks, AK 99775-6160 United States
AU: Domine, F
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320 United States
AU: Domine, F
AF: International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Drive, P.O. Box 757340, Fairbanks, AK 99775-7340 United States
AU: Domine, F
AF: CNRS, Glaciology Laboratory, 54, rue Moliere, B.P. 96, Saint-Martin d'Heres, 38402 France
AU: Simpson, W
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, P.O. Box 757320, Fairbanks, AK 99775-7320 United States
AU: Simpson, W
AF: Department of Chemistry, University of Alaska Fairbanks, 900 Yukon Drive, Fairbanks, AK 99775-6160 United States
AU: Houdier, S
AF: CNRS, Glaciology Laboratory, 54, rue Moliere, B.P. 96, Saint-Martin d'Heres, 38402 France
AU: Douglas, T
AF: Cold Regions Research and Engineering Laboratory, P.O. Box 35170, Fort Wainwright, AK 99703-0170 United States
AU: Sturm, M
AF: Cold Regions Research and Engineering Laboratory, P.O. Box 35170, Fort Wainwright, AK 99703-0170 United States
AU: Stolzberg, R
AF: Department of Chemistry, University of Alaska Fairbanks, 900 Yukon Drive, Fairbanks, AK 99775-6160 United States
AB: In recent years, many studies have highlighted the impact of photochemical reactions in snow on tropospheric chemistry. Snow metamorphism is another factor that affects snow-air interactions. Metamorphism consists of sublimation/condensation cycles driven by temperature gradients. It results in dramatic modifications of the physical properties of the snowpack that lead to exchanges of trace gases with the atmosphere. Even in the absence of light, the chemical compositions of both the snowpack and the troposphere are affected, influencing the chemical signal in ice cores. To better understand exchanges caused by physical processes, we undertook a winter-long study of a snowpack undergoing high-temperature gradient metamorphism, in Fairbanks, central Alaska. To monitor their relative influence on one another, we coupled our physical investigation of the snowpack (temperature, density, crystal morphology, specific surface area, permeability) to chemical measurements (ions, aldehydes, water isotopes). The effects of metamorphic intensity were studied by monitoring the evolution of a similar snowpack subjected to very low temperature gradients. This was achieved by letting the snowpack form on tables, under which air circulation allowed isothermal conditions. A much enhanced permeability and a faster decrease in specific surface area are observed under natural conditions compared to the table experiments. These characteristics considerably impact the concentration of chemical compounds within the snowpack and consequences on their remobilization depend on whether they are present as dissolved gases or particles. Gases such as formaldehyde are strongly released to the atmosphere under high grade metamorphism, while particulate species are less affected by the intensity of metamorphism. These data show that metamorphic intensity significantly influences snow composition, for a constant atmospheric composition. Climate change will decrease temperature gradients in the snow cover and thus modify chemical signals in ice cores. This paper attempts to elucidate the relationship between these two variables.
DE: 9315 Arctic region
DE: 3344 Paleoclimatology
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting