Spatiotemporal variability of elemental and organic carbon in Svalbard snow during 2007–2018

Abstract. Light-absorbing carbonaceous aerosols emitted by biomass or fossil fuel combustion can contribute to amplify Arctic climate warming by lowering the albedo of snow. The Svalbard archipelago, being near to Europe and Russia, is particularly affected by these pollutants, and improved knowledge of their distribution in snow is needed to assess their impact. Here we present and synthesize new data obtained on Svalbard between 2007 and 2018, comprising 324 measurements of elemental (EC) and organic carbon (OC) in snow from 49 sites. We used these data, combined with meteorological and aerosol data and snowpack modelling, to investigate the variability of EC and OC deposition in Svalbard snow across latitude, longitude, elevation and time. Overall, EC concentrations (C_snow^EC) ranged from < 1.0 to 266.6 ng g⁻¹, while OC concentrations (C_snow^OC) ranged from < 1.0 to 9449.1 ng g⁻¹, with the highest values observed near Ny-Ålesund. Calculated snowpack loadings (L_snow^EC, L_snow^OC) in April 2016 were 0.1 to 16.2 mg m⁻² and 1.7 to 320.1 mg m⁻², respectively. The median C_snow^EC and L_snow^EC in the late 2015‒16 winter snowpack on glaciers were close to or lower than those found in earlier (2007–09), comparable surveys. Both L_snow^EC and L_snow^OCC increased exponentially with elevation and snow accumulation, with dry deposition likely playing a minor role. Estimated area-averaged snowpack loads across Svalbard were 1.8 mg EC m⁻² and 71.5 mg OC m⁻² in April 2016. An ~ 11-year long dataset of spring surface snow measurements from central Brøgger Peninsula was used to quantify the interannual variability of EC and OC deposition in snow. On average, C_snow^EC and C_snow^OC at Ny-Ålesund (50 m a.s.l.) were 3 and 7 times higher, respectively, than on the nearby Austre Brøggerbreen glacier (456 m a.s.l.), and the median EC/OC in Ny-Ålesund was 6 times higher, pointing to some local EC emission from Ny-Ålesund. While no long-term trends between 2011 and 2018 were found, C_snow^EC and C_snow^OC showed synchronous variations at Ny-Ålesund and Austre Brøggerbreen. Comparing C_snow^EC at Austre Brøggerbreen with aerosol data from Zeppelin Observatory, we found that snowfall washout ratios between 10 and 300 predict a range of C_snow^EC in agreement with that measured in surface snow. Together, results from this study and comparable surveys confirm the existence of a longitudinal gradient in EC deposition across the Arctic and sub-Arctic, with the lowest C_snow^EC found in the western Arctic (Alaska, Yukon) and central Greenland, and the highest in northwestern Russia and Siberia.