Nitrate stable isotopes and major ions in snow and ice samples from four Svalbard sites

Abstract

Increasing reactive nitrogen (Nr) deposition in the Arctic may adversely impact N-limited ecosystems. To investigate atmospheric transport of Nr to Svalbard, Norwegian Arctic, snow and firn samples were collected from glaciers and analysed to define spatial and temporal variations (1-10 years) in major ion concentrations and the stable isotope composition (δ15N and δ18O) of nitrate (NO-3) across the archipelago. The δ15NNO-3 and δ18ONO-3 averaged -4‰ and 67‰in seasonal snow (2010-11) and -9‰and 74‰in firn accumulated over the decade 2001-2011. East-west zonal gradients were observed across the archipelago for some major ions (non-sea salt sulphate and magnesium) and also for δ15NNO-3 and δ18ONO-3 in snow, which suggests a different origin for air masses arriving in different sectors of Svalbard. We propose that snowfall associated with long-distance air mass transport over the Arctic Ocean inherits relatively low δ15NNO-3 due to in-transport N isotope fractionation. In contrast, faster air mass transport from the north-west Atlantic or northern Europe results in snowfall with higher δ15NNO-3 because in-transport fractionation of N is then time-limited.