Articles | Volume 15, issue 13
Research article
07 Jul 2015
Research article |  | 07 Jul 2015

800-year ice-core record of nitrogen deposition in Svalbard linked to ocean productivity and biogenic emissions

I. A. Wendl, A. Eichler, E. Isaksson, T. Martma, and M. Schwikowski

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+.

Short summary
Nitrate and ammonium ice core records from Lomonosovfonna, Svalbard, indicated anthropogenic pollution from Eurasia as major source during the 20th century. In pre-industrial times nitrate is correlated with methane sulfonate, which we explain with a fertilising effect, presumably triggered by enhanced atmospheric nitrogen input to the ocean. Eurasia was likely the main source area also of pre-industrial nitrate, but for ammonium, biogenic emissions from Siberian boreal forests were dominant.
Final-revised paper