Abstract
In the Arctic areas, the influence of global climate change is enhanced. Enabling a better understanding of the changes in the Arctic environment is of the utmost importance. The deposition of local and long-range transported air pollutants includes light-absorbing aerosols, such as black carbon (BC), which darken bright surfaces and induce snow melt. In 2009–2013, surface snow was sampled on a weekly basis during autumn, winter and spring at the Arctic Space Centre of the Finnish Meteorological Institute in Sodankylä, which is located north of the Arctic Circle (67.37o N, 26.63o E). Snow samples were analyzed for BC with an Organic/Elemental Carbon Aerosol (OCEC) analyzer. These data were combined with SILAM modeling (System for Integrated modeLing of Atmospheric coMposition) to reveal the origin and temporal variability of BC in seasonal snow. Quantitative footprint calculations for the BC observations were performed with the SILAM -model considering emission sources at all heights and including also the sensitivity to the local and near-surface sources. The median BC concentration in snow was 25 µg/kg (n = 107, skewness γ1 = 0.12, 75th percentile Q3 = 42 µg/kg), determined as [μg-EC/L-H2O]. During snow accumulation season, the median surface snow BC concentration was 21µg/kg (n = 78, γ1 = 1.5, Q3 = 33 µg/kg), and during melt season, it was 57 µg/kg (n = 29, γ1 = 2.2, Q3 = 85 µg/kg). The melt period was identified using snow depth data from the Sodankylä station. The highest BC values in spring represented the enrichment of BC to the snow surface due to seasonal snow melt. The spring melt BC enrichment ratio was 2.7 (calculated as the ratio of median melt season concentration to median accumulation season snow concentration). The results showed that increased surface snow BC concentrations (> 30 µg/kg) were due to air masses originating from the Murmansk region in Russia, where smelting and mining industries are located. The temporal variability of BC in snow was high and depended on atmospheric and cryospheric processes, mostly the origin of BC due to atmospheric transport and dry and wet deposition processes, as well as post-depositional snow processes.
Highlights
The influence of climate change is enhanced in the Arctic in comparison to other areas (Serreze and Barry, 2011)
The modeling results showed that increased surface snow black carbon (BC) concentrations (>30 μg/kg) were due to air masses originating from the Murmansk region, Kola Peninsula, Russia, where smelting and mining industries are located (Figure 5)
The aim was to investigate the origin and temporal variability of black carbon observed in surface snow in Sodankylä, north of the Arctic Circle
Summary
The influence of climate change is enhanced in the Arctic in comparison to other areas (Serreze and Barry, 2011). Ice-albedo feedback is greatly influenced by the deposition of local pollution and pollution transported over long distances. This includes light-absorbing aerosols, such as black carbon (BC), which darken bright surfaces, induce snow melt, and enhance Arctic climate change (IPCC, 2019). Various cryospheric and climatic impacts of BC in snow and ice have been widely investigated (e.g., Forsström et al, 2009; Doherty et al, 2010; Meinander et al, 2014; Peltoniemi et al, 2015), and detailed scientific assessments have been presented in Bond et al (2013), in the Arctic Monitoring Assessment Programme report (AMAP, 2015) and in the Intergovernmental Panel on Climate Change report (IPCC, 2019)
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