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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-140
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
30 May 2017
Review status
This discussion paper is under review for the journal Biogeosciences (BG).
Spatial variations in snowpack chemistry and isotopic composition of NO3 along a nitrogen deposition gradient in West Greenland
Chris J. Curtis1,5, Jan Kaiser2, Alina Marca2, N. John Anderson3, Gavin Simpson4,5, Vivienne Jones5, and Erika Whiteford3 1School of Geography, Archaeology & Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa
2Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
3Dept of Geography, Loughborough University, UK
4Dept of Biology, University of Regina, Saskatchewan, Canada
5ECRC, Dept of Geography, University College London, Gower Street, London, UK
Abstract. Snowpack chemistry, nitrate stable isotopes and net deposition fluxes for the largest ice-free region in Greenland were investigated to determine whether there are spatial gradients from the ice sheet margin to the coast linked to a gradient in precipitation. Late-season snowpack was sampled in March 2011 at 8 locations within 3 lake catchments in each of 3 regions (ice sheet margin in the east, central area near Kelly Ville and the coastal zone to the west). At the coast, snowpack accumulation averaged 181 mm snow water equivalent (SWE), compared with 36 mm SWE by the ice sheet. Coastal snowpack showed significantly greater concentrations of marine salts (Na+, Cl, other major cations), ammonium (regional means 1.4–2.7 µmol L−1), total and non-sea salt sulfate (total 1.8–7.7, non-sea salt 1.0–1.8 µmol L−1) than the two inland regions. Nitrate (1.5–2.4 µmol L−1) showed significantly lower concentrations at the coast. Despite lower concentrations, higher precipitation at the coast results in a strong deposition gradient for NO3 as well as NH4+ and non-sea salt sulfate (nss-SO42−) increasing from the inland regions to the coast (lowest at Kelly Ville 6, 4 and 3; highest at coast 9, 17 and 11 mol ha−1 yr−1 of NO3, NH4+ and nss-SO42− respectively). The δ(15N) of snowpack NO3 shows a significant decrease from the ice sheet margin (−7.5 ‰) to the coast (−11.3 ‰). We attribute the spatial gradient of δ(15N) in SW Greenland to post-deposition processing rather than differing sources because of (1) the climatic gradient from ice sheet margin to coast, (2) within-catchment isotopic differences between terrestrial snowpack and lake-ice snowpack, and (3) similarities between fresh snow (rather than accumulated snowpack) at Kelly Ville and the coast. Hence the δ(15N) of coastal snowpack is most representative of snowfall in SW Greenland, but after deposition the effects of photolysis, volatilization and sublimation lead to enrichment of the remaining snowpack with the greatest effect in inland areas of low precipitation and high sublimation losses.

Citation: Curtis, C. J., Kaiser, J., Marca, A., Anderson, N. J., Simpson, G., Jones, V., and Whiteford, E.: Spatial variations in snowpack chemistry and isotopic composition of NO3 along a nitrogen deposition gradient in West Greenland, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-140, in review, 2017.
Chris J. Curtis et al.
Chris J. Curtis et al.
Chris J. Curtis et al.

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Short summary
Few studies have investigated the atmospheric deposition of nitrate in the Arctic or its impacts on Arctic ecosystems. We collected late season snowpack from 3 regions of W Greenland from the coast to the edge of the ice sheet. We found major differences in nitrate concentrations (lower at the coast) and deposition load (higher at the coast). Nitrate in snowpack undergoes losses and isotopic enrichment which are greatest in inland areas, hence deposition impacts may be greatest at the coast.
Few studies have investigated the atmospheric deposition of nitrate in the Arctic or its impacts...
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