Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 2
Biogeosciences, 15, 529-550, 2018
https://doi.org/10.5194/bg-15-529-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 15, 529-550, 2018
https://doi.org/10.5194/bg-15-529-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Jan 2018

Research article | 29 Jan 2018

Spatial variations in snowpack chemistry, isotopic composition of NO3 and nitrogen deposition from the ice sheet margin to the coast of western Greenland

Chris J. Curtis1,6, Jan Kaiser2, Alina Marca2, N. John Anderson3, Gavin Simpson4,5,6, Vivienne Jones6, and Erika Whiteford3 Chris J. Curtis et al.
  • 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, Loughborough, UK
  • 4Institute of Environmental Change & Society, University of Regina, Saskatchewan, Canada
  • 5Dept of Biology, University of Regina, Saskatchewan, Canada
  • 6ECRC, Dept of Geography, University College London, Gower Street, London, UK

Abstract. The relative roles of anthropogenic nitrogen (N) deposition and climate change in causing ecological change in remote Arctic ecosystems, especially lakes, have been the subject of debate over the last decade. Some palaeoecological studies have cited isotopic signals (δ(15N)) preserved in lake sediments as evidence linking N deposition with ecological change, but a key limitation has been the lack of co-located data on both deposition input fluxes and isotopic composition of deposited nitrate (NO3). In Arctic lakes, including those in western Greenland, previous palaeolimnological studies have indicated a spatial variation in δ(15N) trends in lake sediments but data are lacking for deposition chemistry, input fluxes and stable isotope composition of NO3. In the present study, snowpack chemistry, NO3 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 eight locations within three lake catchments in each of three regions (ice sheet margin in the east, the central area near Kelly Ville and the coastal zone to the west). At the coast, snowpack accumulation averaged 181mm snow water equivalent (SWE) compared with 36mm SWE by the ice sheet. Coastal snowpack showed significantly greater concentrations of marine salts (Na+, Cl, other major cations), ammonium (NH4+; regional means 1.4–2.7µmolL−1), total and non-sea-salt sulfate (SO42−; total 1.8–7.7, non-sea-salt 1.0–1.8µmolL−1) than the two inland regions. Nitrate (1.5–2.4µmolL−1) showed significantly lower concentrations at the coast. Despite lower concentrations, higher precipitation at the coast results in greater net deposition for NO3 as well as NH4+ and non-sea-salt sulfate (nss-SO42−) relative to the inland regions (lowest at Kelly Ville 6, 4 and 3; highest at coast 9, 17 and 11molha−1a−1 of NO3, NH4+ and nss-SO42− respectively). The δ(15N) of snowpack NO3 shows a significant decrease from inland regions (−5.7‰ at Kelly Ville) to the coast (−11.3‰). We attribute the spatial patterns of δ(15N) in western Greenland to post-depositional processing rather than differing sources because of (1) spatial relationships with precipitation and sublimation, (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 western 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.

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Few studies have investigated the atmospheric deposition of nitrate in the Arctic or its impacts on Arctic ecosystems. We collected late-season snowpack from three regions in western 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). 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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