HR: 1340h
AN: A53B-1150    [Abstracts]
TI: Salt Distributions in the Sea-Ice Snowpack and Implications for Arctic Halogen Activation
AU: * Carlson, D
EM: fsdac8@uaf.edu
AF: Department of Chemistry and Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, United States
AU: Alvarez-Aviles, L
EM: ftla@uaf.edu
AF: Department of Chemistry and Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, United States
AU: Simpson, W
EM: ffwrs@uaf.edu
AF: Department of Chemistry and Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, United States
AB: Reactive halogens, derived from sea salt, are important oxidizers affecting arctic atmospheric chemistry. Bromine, and to a lesser extent chlorine and iodine, are periodically sourced, particularly during springtime, into the arctic atmosphere in the atomic or halogen oxide radical forms. These species subsequently cause depletions of surface ozone, deposit atmospheric mercury into the snowpack, and significantly change the overall oxidizing capacity and pattern of oxidation within the atmosphere. The process by which reactive halogens are released into the atmosphere is not understood, but has been linked to heterogeneous reactions on frozen surfaces that contain salts. Aerosols, frost-flowers, and open water leads have all been proposed as possible atmospheric halogen sources, but recent evidence suggests that snow on sea-ice might be the most important contributor. To better understand the impact of snow on arctic halogen chemistry, atmospherically accessible snow on various types of sea-ice were sampled from the University of Washington Applied Physics Laboratory Ice Station (APLIS 07) Beaufort Sea ice camp. Salt distributions were measured by means of bulk conductivity and ion chromatography. The high bulk salinities found support the idea of snow that has wicked up salts from newly formed sea-ice as a significant atmospheric halogen source. The resulting distributions show distinct differences in snowpack salinities on the different types of underlying sea-ice. The heterogeneous chemistry of halogen activation is likely to not depend upon the bulk salinity but instead on the surface salinity of the snow. From laboratory studies and theoretical considerations, there appears to be a saturation behavior where highly saline samples react at similar rates to less saline samples. Therefore, one needs to understand distributions of salinity and ion contents in snow to predict reactivity with respect to halogen activation. These distributions could be used with surface reactivity data and remotely sensed sea-ice data to model activated halogen inputs into the arctic atmosphere.
DE: 0365 Troposphere: composition and chemistry
DE: 0736 Snow (1827, 1863)
DE: 0750 Sea ice (4540)
DE: 9315 Arctic region (0718, 4207)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting