Organic Compounds, Radiocarbon, Trace Elements and Atmospheric Transport Illuminating Sources of Elemental Carbon in a 300‐Year Svalbard Ice Core.

Black carbon (BC) particles produced by incomplete combustion of biomass and fossil fuels warm the atmosphere and decrease the reflectivity of snow and ice, hastening their melt. Although the significance of BC in Arctic climate change is widely acknowledged, observations on its deposition and sources are few. We present BC source types in a 300‐year (1700–2005) Svalbard ice core by analysis of particle‐bound organic compounds, radiocarbon, and trace elements. According to the radiocarbon results, 58% of the deposited elemental carbon (EC, thermal‐optical proxy of BC) is of non‐fossil origin throughout the record, while the organic compounds suggest a higher percentage (68%). The contribution of fossil fuels to EC is suggested to have been elevated between 1860 and 1920, particularly based on the organics and trace element data. A second increase in fossil fuel sources seems to have occurred near the end of the record: according to radiocarbon measurements between 1960 and 1990, while the organics and trace element data suggest that the contribution of fossil fuels has increased since the 1970s to the end of the record, along with observed increasing EC deposition. Modeled atmospheric transport between 1948 and 2004 shows that increasing EC deposition observed at the glacier during that period can be associated with increased atmospheric transport from Far East Asia. Further observational BC source data are essential to help target climate change mitigation efforts. The combination of robust radiocarbon with organic compound analyses requiring low sample amounts seems a promising approach for comprehensive Arctic BC source apportionment. Plain Language Summary: Black carbon (BC) is a fine particulate emission component formed in natural and anthropogenic combustion of biomass and fossil fuels. BC effectively warms the atmosphere, and when it is deposited on snow and ice, it hastens their melt. BC strongly amplifies Arctic climate change but information on its deposition variations and sources are still very scarce. We studied sources of BC in a Svalbard (high‐Arctic) ice core covering the years 1700–2005 by analysis of chemical compounds, radiocarbon and trace elements. We found that throughout the ice core, the contribution of biomass combustion to BC was higher (ca. 60%–70%) than that of fossil fuels. The contribution of fossil fuel sources to BC in the ice core was elevated in 1860–1920, and again at the end of the record starting in the 1960s–1970s. Atmospheric transport modeling shows that increasing BC deposition observed at the glacier since the 1970s was associated with airmasses arriving increasingly from Far East Asia. Further observations on Arctic BC sources are essential to inform decision makers on which BC emissions most affect Arctic climate change. Key Points: Non‐fossil sources have dominated (ca. 60%–70%) elemental carbon (EC) deposition in a Svalbard ice core between 1700 and 2005The contribution of fossil fuels to EC was highest between 1860 and 1920 and toward the end of the record starting in the 1960s or 1970sAtmospheric transport modeling indicates that observed increased EC deposition was associated with potential Asian sources in 1948–2004 [ABSTRACT FROM AUTHOR]