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AGU: Journal of Geophysical Research, Atmospheres

 

Keywords

  • O-17
  • nitrate
  • Greenland

Index Terms

  • Atmospheric Composition and Structure: Geochemical cycles
  • Geochemistry: Stable isotope geochemistry
  • Cryosphere: Ice cores
  • Biogeosciences: Trace element cycling
  • Biogeosciences: Paleoclimatology and paleoceanography
Abstract
Cited By (0)
 

Abstract

Measurements and modeling of Δ17O of nitrate in snowpits from Summit, Greenland

S. A. Kunasek

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

B. Alexander

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

E. J. Steig

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

M. G. Hastings

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, Washington, USA

D. J. Gleason

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

J. C. Jarvis

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

We quantify controls on seasonal changes of the oxygen isotope anomaly of nitrate (Δ17O(NO3 −), wherein Δ17O ≈ δ 17O − (0.52 × δ 18O)) in snow at Summit, Greenland, in an effort to enable quantitative reconstructions of paleoatmospheric oxidant concentrations from ice core Δ17O(NO3 −). Measurements of Δ17O(NO3 −) from a snowpit at Summit are compared to calculations from an atmospheric chemical box model. Measured values of Δ17O(NO3 −) covering three seasonal cycles (January–December 2000, July 2003–March 2006) range from 22.4‰ in summertime to 33.7‰ in wintertime, while model results show a larger range (18.9–31.5‰). Agreement between observed and modeled results is excellent for winter, when O3 oxidation of nitrogen oxides dominates nitrate production (winter averages agree within 0.3‰). The 2–7‰ discrepancy between summertime box model results and measurements of Δ17O(NO3 −) may result from several influences not accounted for by our box model, including nonzero Δ17O of OH over polar regions, stratospheric influence on surface O3 at Summit, participation of BrO in nitrate production, and tropospheric transport of nitrate. A box model sensitivity study shows that annual mean Δ17O(NO3 −) is most sensitive to changes in the ratio of [O3]/([HO2] + [RO2]) in summer.

Received 23 May 2008; accepted 1 October 2008; published 20 December 2008.

Citation: Kunasek, S. A., B. Alexander, E. J. Steig, M. G. Hastings, D. J. Gleason, and J. C. Jarvis (2008), Measurements and modeling of Δ17O of nitrate in snowpits from Summit, Greenland, J. Geophys. Res., 113, D24302, doi:10.1029/2008JD010103.

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