Open AccessFormaldehyde in the Alaskan Arctic snowpack: Partitioning and physical processes involved in air‐snow exchanges
Author(s) -
Barret Manuel,
Domine Florent,
Houdier Stephan,
Gallet JeanCharles,
Weibring Petter,
Walega James,
Fried Alan,
Richter Dirk
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jd016038
Subject(s) - snow , snowpack , atmospheric sciences , flux (metallurgy) , atmosphere (unit) , deposition (geology) , arctic , formaldehyde , albedo (alchemy) , diffusion , environmental science , firn , mineral dust , snow field , aerosol , environmental chemistry , chemistry , meteorology , geology , snow cover , geography , physics , oceanography , thermodynamics , geomorphology , structural basin , art , organic chemistry , performance art , art history
The snowpack is a photochemically active medium which produces numerous key reactive species involved in the atmospheric chemistry of polar regions. Formaldehyde (HCHO) is one such reactive species produced in the snow, and which can be released to the atmospheric boundary layer. Based on atmospheric and snow measurements, this study investigates the physical processes involved in the HCHO air‐snow exchanges observed during the OASIS 2009 field campaign at Barrow, Alaska. HCHO concentration changes in a fresh diamond dust layer are quantitatively explained by the equilibration of a solid solution of HCHO in ice, through solid‐state diffusion of HCHO within snow crystals. Because diffusion of HCHO in ice is slow, the size of snow crystals is a major variable in the kinetics of exchange and the knowledge of the snow specific surface area is therefore crucial. Air‐snow exchanges of HCHO can thus be explained without having to consider processes taking place in the quasi‐liquid layer present at the surface of ice crystals. A flux of HCHO to the atmosphere was observed simultaneously with an increase of HCHO concentration in snow, indicating photochemical production in surface snow. This study also suggests that the difference in bromine chemistry between Alert (Canadian Arctic) and Barrow leads to different snow composition and post‐deposition evolutions. The highly active bromine chemistry at Barrow probably leads to low HCHO concentrations at the altitude where diamond dust formed. Precipitated diamond dust was subsequently undersaturated with respect to thermodynamic equilibrium, which contrasts to what was observed elsewhere in previous studies.