EGU24-548, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Isotope analysis of snowpack nitrate in coastal Antarctica; evidence of nitrate photolysis and preservation.

Amelia Bond1, Markus M. Frey1, Jan Kaiser2, Alina Marca2, and Freya Squires1
Amelia Bond et al.
  • 1British Antarctic Survey, Cambridge, UK
  • 2School of Environmental Sciences, University of East Anglia, Norwich, UK

Photolysis of snowpack nitrate results in emission of the reactive nitrogen species NOx and HONO. These are important pre-cursors of HOx radicals and ozone, and thereby affect the oxidising capacity of the lower atmosphere above remote snow-covered areas. This is of particular importance in the polar regions as the usual OH radical formation pathway (ozone photolysis and reaction of O(1D) with H2O) is limited by the low water vapour concentration. Isotope analysis of atmospheric reactive nitrogen species and snow nitrate is proving to be a crucial tool for elucidating mechanisms of reactive nitrogen cycling in and above snow.

The first snowpit profiles of nitrate stable isotopes (δ15N, δ18O) and concentration at Halley VI Research Station in coastal Antarctica will be presented. The observed isotope fractionation provides evidence of photochemical loss of nitrate and allows estimation of the photolytic isotope fractionation constant at the site. At this high accumulation site, the peak in nitrate concentration from the previous summer is preserved below the snow surface, unlike at low accumulation sites on the Antarctic Plateau. Combining measurements of nitrate concentration and its isotopic compositions preserved in snow helps disentangle the isotope signature of seasonal changes in atmospheric nitrate sources from post-depositional isotope fractionation occurring even at high snow accumulation sites.

How to cite: Bond, A., Frey, M. M., Kaiser, J., Marca, A., and Squires, F.: Isotope analysis of snowpack nitrate in coastal Antarctica; evidence of nitrate photolysis and preservation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-548,, 2024.