Tagged tracer simulations of black carbon in the Arctic: transport, source contributions, and budget

Abstract

Abstract. We implemented a tagged tracer method of black carbon (BC) into a global chemistry transport model, GEOSChem, examined the pathways and efficiency of long-range transport from a variety of anthropogenic and biomass burning emission sources to the Arctic, and quantified the source contributions of individual emissions. Firstly, we evaluated the simulated BC by comparing it with observations at the Arctic sites and examined the sensitivity of an aging parameterization and wet scavenging rate by ice clouds. For tagging BC, we added BC tracers distinguished by source types (anthropogenic and biomass burning) and regions; the global domain was divided into 16 and 27 regions for anthropogenic and biomass burning emissions, respectively. Our simulations showed that BC emitted from Europe and Russia was transported to the Arctic mainly in the lower troposphere during winter and spring. In particular, BC transported from Russia was widely spread over the Arctic in winter and spring, leading to a dominant contribution of 62 % to the Arctic BC near the surface as the annual mean. In contrast, BC emitted from East Asia was found to be transported in the middle troposphere into the Arctic mainly over the Sea of Okhotsk and eastern Siberia during winter and spring. We identified an important "window" area, which allowed a strong incoming of East Asian BC to the Arctic (130-180 • E and 3-8 km of altitude at 66 • N). The model demonstrated that the contribution from East Asia to the Arctic had a maximum at about 5 km of altitude due to uplifting during long-range transport in early spring. The efficiency of BC transport from East Asia to the Arctic was lower than that from other large source regions such as Europe, Russia, and North America. However, the East Asian contribution was the most important for BC in the middle troposphere (41 %) and the BC burden over the Arctic (27 %) because of the large emissions from this region. These results suggested that the main sources of Arctic BC differed with altitude. The contribution of all the anthropogenic sources to Arctic BC concentrations near the surface was dominant (90 %) on an annual basis. The contributions of biomass burning in boreal regions (Siberia, Alaska, and Canada) to the annual total BC deposition onto the Arctic were estimated to be 12-15 %, which became the maximum during summer.

Source attribution of Arctic black carbon constrained by aircraft and surface measurements

“…The dominant role of eastern and southern Asia in the middle troposphere is consistent with Ikeda et al (2017), who studied the source attribution of Arctic BC using a tagged tracer method in GEOS-Chem with the HTAP v2.2 emission inventory. The largest contribution from eastern and southern Asia to Arctic BC burden in this study is also consistent with Ma et al (2013) and Wang et al (2014).…”

“…Stohl, 2006;Shindel et al, 2008;Hirdman et al, 2010;Wang et al, 2014) while others found eastern and southern Asia had the largest contribution (Koch and Hansen, 2005;Ikeda et al, 2017). Some studies suggested that Europe was the dominant source of BC aloft (Stohl, 2006;Huang et al, 2010b) while others found eastern and southern Asia was the most important source (Sharma et al, 2013;Breider et al, 2014;Wang et al, 2014;Ikeda et al, 2017) in the middle troposphere. Recent work by Stohl et al (2013) and Sand et al (2016) raised questions about prior studies by identifying the importance of seasonally varying residential heating and by suggesting a significant overlooked source from gas flaring in high-latitude regions.…”

“…Some studies attributed the surface BC primarily to emissions in highlatitude regions including Europe and northern Eurasia (e.g. Stohl, 2006;Shindel et al, 2008;Hirdman et al, 2010;Wang et al, 2014) while others found eastern and southern Asia had the largest contribution (Koch and Hansen, 2005;Ikeda et al, 2017). Some studies suggested that Europe was the dominant source of BC aloft (Stohl, 2006;Huang et al, 2010b) while others found eastern and southern Asia was the most important source (Sharma et al, 2013;Breider et al, 2014;Wang et al, 2014;Ikeda et al, 2017) in the middle troposphere.…”

Processes Controlling the Composition and Abundance of Arctic Aerosol

“…Long aerosol lifetimes and descent from the upper and middle troposphere can allow aerosol transported from lower latitudes to influence the lower Arctic troposphere, but the extent of this influence and its seasonality remains poorly constrained (e.g., Koch & Hansen, ; Stohl, ; Willis et al, ). Evidence from vertically resolved in situ and satellite observations suggests that the seasonal maximum in aerosol concentrations aloft may occur later than at the Arctic surface (Di Pierro et al, ; Ikeda et al, ; Scheuer et al, ; Stohl, ); however, the extent to which aerosol aloft correlates with aerosol observed near the surface remains an important question. The challenge in resolving these questions arises partly from the difficulty of making regular vertically resolved measurements of the Arctic atmosphere, especially in dark months, and consequently chemically detailed data are limited.…”

Current and Future Arctic Aerosols and Ozone From Remote Emissions and Emerging Local Sources—Modeled Source Contributions and Radiative Effects

“…Anthropogenic emissions from Europe, Asia, and North America in the midlatitudes are currently the main source of Arctic pollution, especially in winter and spring when poleward atmospheric transport is efficient and removal processes are weak (Barrie, 1986;Stohl, 2006). Biomass burning at middle and high latitudes is also an important source of Arctic pollution during late spring and summer (Brock et al, 1989;Ikeda et al, 2017;Stohl, 2006;Warneke et al, 2009), although its exact contribution is uncertain. These remote emissions are an important source of Arctic aerosols (e.g., black carbon [BC] and sulfate) and ozone, which act as short-lived climate forcers that can enhance or mitigate the observed rapid Arctic warming (Arctic Monitoring and Assessment Programme [AMAP], 2015; Najafi et al, 2015;Shindell et al, 2006).…”