First ice core records of NO3− stable isotopes from Lomonosovfonna, Svalbard

Abstract

AbstractSamples from two ice cores drilled at Lomonosovfonna, Svalbard, covering the period 1957–2009, and 1650–1995, respectively, were analyzed for NO3−concentrations, and NO3− stable isotopes (δ15N and δ18O). Post‐1950 δ15N has an average of (−6.9 ± 1.9)‰, which is lower than the isotopic signal known for Summit, Greenland but agrees with values observed in recent Svalbard snow and aerosol. Pre‐1900 δ15N has an average of (4.2 ± 1.6)‰ suggesting that natural sources, enriched in the 15 N isotope, dominated before industrialization. The post‐1950 δ18O average of (75.1 ± 4.1)‰ agrees with data from low and polar latitudes, suggesting similar atmospheric NOy (NOy = NO + NO2 + HNO3) processing pathways. The combination of anthropogenic source δ15N and transport isotope effect was estimated as −29.1‰ for the last 60 years. This value is below the usual range of NOx (NOx = NO + NO2) anthropogenic sources which is likely the result of a transport isotope effect of −32‰. We suggest that the δ15N recorded at Lomonosovfonna is influenced mainly by fossil fuel combustion, soil emissions, and forest fires; the first and second being responsible for the marked decrease in δ15N observed in the post‐1950s record with soil emissions being associated to the decreasing trend in δ15N observed up to present time, and the third being responsible for the sharp increase of δ15N around 2000.