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| Titel |
Atmospheric nitrogen oxides (NO and NO2) at Dome C: first observations and implications for reactive nitrogen cycling above the East Antarctic Ice Sheet |
| VerfasserIn |
M. M. Frey, N. Brough, J. L. France, M. D. King, J. Erbland, J. Savarino, P. S. Anderson, A. E. Jones, E. W. Wolff |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039735
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| Zusammenfassung |
| The nitrogen oxides NO and NO2 (NOx) play a key role in determining the oxidizing
capacity of the boundary layer in high latitudes. This influence is achieved via the photolysis
of NO2 – the only source for in situ production of tropospheric ozone (O3) – and through
shifting HOx radical partitioning towards the hydroxyl radical (OH) via the reaction NO +
HO2 - OH + NO2. Previous field campaigns in the Arctic and Antarctic have demonstrated
that the polar snow pack can release significant emissions of NOx and that one of the
major driving mechanisms is UV-photolysis of snow nitrate (NO3-). Unusually
high levels of NO observed at South Pole and on an airborne campaign suggested
that the East Antarctic Ice Sheet (EAIS) can be perceived as a gigantic chemical
reactor, processing many chemical trace species at the surface and thereby modifying
their concentration eventually preserved in ice cores. However, the database for a
quantitative understanding of reactive nitrogen recycling across Antarctica is still
weak.
Here, we present first measurements of atmospheric NOx mixing ratios and fluxes at Dome C
(DC), East Antarctica (75.1ºS 123.3ºE, 3233 m) during austral summer 2009/2010. As seen
previously, NO mixing ratios were highly perturbed, ranging between 10 pptv and >600 pptv,
but unlike at South Pole showed a strong diurnal variability. Concentration maxima occurring
in the evening hours coincided with the strongest gradients between the snow surface and 4.0
m, highlighting the importance of the interplay between snow pack source strength and the
evolution of boundary layer depth. Conversely, surface-near firn air levels of NOx varied in
phase with solar radiation, consistent with a photolytic source in the surface-near
snow. Observed NOx emissions were compared to calculations based on NO3-
concentration profiles and e-folding depths of actinic flux measured in the upper
snowpack.
Contrary to South Pole, surface observations at DC are thought to be more representative for
the wider East Antarctic plateau region and are discussed as a significant step towards the
parameterization of NOx emissions in a quantitative model of reactive nitrogen recycling
above Antarctica. |
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