An inverse model for corrections of the effects of post-depositional processing on snow nitrate: ice-core applications and preliminary results
Abstract
Atmospheric nitrate preserved in ice cores has been sought to provide information on past variability in atmospheric NOx, and the Δ17O of ice core nitrate is a proxy to reconstruct atmospheric oxidants. However, the photo-driven post-depositional processing of snow nitrate leads to changes in nitrate concentrations and its isotopic composition (δ15N and Δ17O) relative to the original atmospheric signals. Such changes must be quantified and corrected for in order to use ice-core nitrate records to retrieve past information on atmospheric NOxand oxidant abundances. Here we introduce an inverse snow photochemical column model to correct for the effects of post-depositional processing. The model uses the preserved nitrate concentrations and isotopes (δ15N and Δ17O), applying layered snow nitrate photochemical mass-balance calculations, to recover the original atmospheric signals, i.e., nitrate deposition flux and δ15N and Δ17O of the deposited nitrate. The model was tested using snowpit and atmospheric aerosol samples from Summit Greenland, and the model matches well with the observed atmospheric nitrate δ15N and Δ17O. The model will be further applied to GISP2 and WAIS divide ice core records of nitrate, to recover glacial-interglacial changes in nitrate deposition flux and its isotopes, and to explore climate driven changes in atmosphere NOxand oxidant abundances. Preliminary results from the ice cores will be shown.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C11C1289G
- Keywords:
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- 0724 Ice cores;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY