Abstract
Abstract. We present the records of the two nitrogen species nitrate (NO3-) and ammonium (NH4+) analysed in a new ice core from Lomonosovfonna, Svalbard, in the Eurasian Arctic covering the period 1222–2009. Changes in melt at the Lomonosovfonna glacier are assumed to have a negligible effect on the decadal variations of the investigated compounds. Accordingly, we use decadal records to investigate the major emission sources of NO3- and NH4+ precursors and find that during the twentieth century both records are influenced by anthropogenic pollution from Eurasia. In pre-industrial times NO3- is highly correlated with methane sulfonate (MSA), which we explain by a fertilising effect. We propose that enhanced atmospheric NO3- concentrations and the corresponding nitrogen input to the ocean trigger the growth of dimethyl-sulfide-(DMS)-producing phytoplankton. Increased DMS production results in elevated fluxes to the atmosphere where it is oxidised to MSA. Eurasia was presumably the main source area also of pre-industrial NO3-, but a more exact source apportionment could not be performed based on our data. This is different for NH4+, where biogenic ammonia (NH3) emissions from Siberian boreal forests were identified as the dominant source of pre-industrial NH4+.
Highlights
The Arctic is generally a nutrient limited region (Dickerson, 1985)
Our finding is in agreement with results from transport modelling and trajectory analysis, identifying Eurasia as a source region for Svalbard (Hirdman et al, 2010a, b)
We presented the 800-year records of the two nitrogen species NO−3 and NH+4 analysed in a new ice core collected from Lomonosovfonna, Svalbard, in 2009
Summary
The Arctic is generally a nutrient limited region (Dickerson, 1985). Nutrients originate from lower latitudes and reach the remote polar areas via long-range transport; local sources are sparse. The major source of bio-available nitrogen in the Arctic is the deposition of reactive atmospheric nitrogen that is present primarily as nitrate (NO−3 ) and ammonium (NH+4 ) (Björkman et al, 2013; Kühnel et al, 2011). NH+4 derives from biogenic emissions of ammonia (NH3) from terrestrial and marine sources, biomass burning, agriculture, and livestock breeding (Fuhrer et al, 1996; Galloway et al, 2004; Wolff, 2013) Both NO−3 and NH+4 concentrations in the atmosphere have varied greatly with time and space due to changing emissions and the short atmospheric lifetimes of a few days (Adams et al, 1999; Feng and Penner, 2007). The deposition of NO−3 and NH+4 in Published by Copernicus Publications on behalf of the European Geosciences Union
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