HR: 08:45h
AN: A21D-04    [Abstracts]
TI: First Observations of Atmospheric Hydrogen Peroxide (H$_{2}$O$_{2}$) and Methylhydroperoxide (CH$_{3}$OOH) in West Antarctica: Comparison of Experiment and Model Results
AU: * Frey, M M
EM: mfrey@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, University of Arizona, 1133 E.North Campus Drive, Tucson, AZ 85721 United States
AU: Stewart, R W
EM: stewart@oasis.gsfc.nasa.gov
AF: Atmospheric Chemistry and Dynamics Branch, National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), Code 130, Greenbelt, MD 20771 United States
AU: McConnell, J R
EM: jmcconn@dri.edu
AF: Desert Research Institute , Divison of Hydrologic Sciences, 2215 Raggio Parkway, Reno, NV 89512 United States
AU: Bales, R C
EM: rbales@ucmerced.edu
AF: University of California, Merced, 4225 N. Hospital Road, Bldg 1200, Atwater, CA 95301 United States
AB: Hydrogen peroxide (H$_{2}$O$_{2}$) and higher organic peroxides such as methylhydroperoxide MHP (CH$_{3}$OOH) are closely linked to chemical feedback mechanisms controlling the composition of the atmosphere. Recent findings in Central Greenland and at the South Pole show that a physical snowpack source is contributing significantly to boundary-layer H$_{2}$O$_{2}$. This has important implications for the current understanding of HO$_{x}$ radical chemistry above extended snow and ice surfaces as well as for the quantitative interpretation of the H$_{2}$O$_{2}$ record from ice cores. Here we report atmospheric measurements of hydroperoxides from three U.S. ITASE traverses, 2000-03. The wide spatial distribution of the 21 traverse sites between $75\deg$S and $90\deg$S, allows investigation of the peroxide photochemistry in the summer troposphere and the impact of the upper snowpack on the boundary layer in varying depositional environments, such as up to a 5-fold change in accumulation rate (8-44 cm SWE/yr) and a 30 K difference in mean annual temperature (-21.4 to $-49.3\deg$C). The only higher organic peroxide detected using a continuous-flow HPLC method is MHP, as expected in the remote atmosphere. Site averages of both, H$_{2}$O$_{2}$ and MHP showed a latitudinal gradient between $75\deg$S and $90\deg$S, decreasing from $803\pm150$ pptv to $230\pm56$ pptv and from $491\pm296$ pptv to $102\pm41$ pptv respectively. The MHP:H$_{2}$O$_{2}$ ratios varied between 0.4 and 2.5 with the higher values occuring during storm events as a consequence of the large difference in water solubility. Model runs using the NASA-Goddard Flight Center (GSFC) point photochemical model match observations of peroxides within the experimental uncertainties only by introducing source fluxes of H$_{2}$O$_{2}$ and HCHO, estimated from measured firn-ambient air ratios. The best model fits put some constraints on levels as well as snowpack fluxes of atmospheric NO$_{x}$ (not measured), ranging from 20 pptv at Byrd Surface Camp ($80\deg$S) to 30-40 pptv at the South Pole.
DE: 3344 Paleoclimatology
DE: 3307 Boundary layer processes
DE: 1863 Snow and ice (1827)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting