Abstract
Abstract. Observations show that the concentrations of Arctic sulfate and black carbon (BC) aerosols have declined since the early 1980s. Previous studies have reported that reducing sulfate aerosols potentially contributed to the recent rapid Arctic warming. In this study, a global aerosol–climate model (Community Atmosphere Model, version 5) equipped with Explicit Aerosol Source Tagging (CAM5-EAST) is applied to quantify the source apportionment of aerosols in the Arctic from 16 source regions and the role of aerosol variations in affecting changes in the Arctic surface temperature from 1980 to 2018. The CAM5-EAST simulated surface concentrations of sulfate and BC in the Arctic had a decrease of 43 % and 23 %, respectively, in 2014–2018 relative to 1980–1984 mainly due to the reduction of emissions from Europe, Russia and local Arctic sources. Increases in emissions from South and East Asia led to positive trends in Arctic sulfate and BC in the upper troposphere. All aerosol radiative impacts are considered including aerosol–radiation and aerosol–cloud interactions, as well as black carbon deposition on snow- and ice-covered surfaces. Within the Arctic, sulfate reductions caused a top-of-atmosphere (TOA) warming of 0.11 and 0.25 W m−2 through aerosol–radiation and aerosol–cloud interactions, respectively. While the changes in Arctic atmospheric BC has little impact on local radiative forcing, the decrease in BC in snow and ice led to a net cooling of 0.05 W m−2. By applying climate sensitivity factors for different latitudinal bands, global changes in sulfate and BC during 2014–2018 (with respect to 1980–1984) exerted a +0.088 and 0.057 K Arctic surface warming, respectively, through aerosol–radiation interactions. Through aerosol–cloud interactions, the sulfate reduction caused an Arctic warming of +0.193 K between the two time periods. The weakened BC effect on snow–ice albedo led to an Arctic surface cooling of −0.041 K. The changes in atmospheric sulfate and BC outside the Arctic produced a total Arctic warming of +0.25 K, the majority of which is due to the midlatitude changes in radiative forcing. Our results suggest that changes in aerosols over the midlatitudes of the Northern Hemisphere have a larger impact on Arctic temperature than other regions through enhanced poleward heat transport. The combined total effects of sulfate and BC produced an Arctic surface warming of +0.297 K, explaining approximately 20 % of the observed Arctic warming since the early 1980s.
Highlights
The Arctic has warmed rapidly since the 1980s with a 1.5 K increase in the surface air temperature, which is about 2 to 4 times faster than the global average (Trenberth et al, 2007; Serreze et al, 2009)
EAST was implemented in CAM5 to quantify the source– receptor relationships of aerosols in recent studies (Wang et al, 2014; Yang et al, 2017a, b, 2018a, b, c)
Different from the emission perturbation method that was often used in previous studies, in this study, the EAST was implemented in CAM5 to quantify the source attribution of aerosols in the Arctic and the aerosol-related Arctic warming during 1980–2018
Summary
The Arctic has warmed rapidly since the 1980s with a 1.5 K increase in the surface air temperature, which is about 2 to 4 times faster than the global average (Trenberth et al, 2007; Serreze et al, 2009). Studies have shown that changes in long-range transport of sulfate and BC aerosols from midlatitude regions have caused strong wintertime warming in the Arctic (e.g., Breider et al, 2014; Fisher et al, 2011; Shindell et al, 2008). Based on simulations of a chemical transport model, Fisher et al (2011) concluded that West Asian emissions dominated wintertime Arctic sulfate concentration with contributions between 30 % and 45 %. In the past few decades, anthropogenic emissions have changed rapidly, with a decrease in Europe and North America and an increase in South and East Asia This may have had an important impact on the Arctic aerosols and climate (Breider et al, 2014).
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