Simulation of black carbon in snow and its climate impact in the Canadian Global Climate Model

Namazi, Maryam; Salzen, Knut von; Cole, Jason N. S.

doi:10.5194/acp-15-10887-2015

Cited by 26 publications

(31 citation statements)

References 79 publications

(101 reference statements)

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“…For example, most of the models with forcing stronger than CanESM2 treat the second indirect effect as well as the first [ Boucher et al , ]; therefore, we could expect to see a stronger impact of declining aerosols on Arctic sea ice in these models. Lastly, the surface effect of BC is missing in our model, but based on recent studies this effect is likely to be small [ Namazi et al , ]. Further investigation of the effect of BC on snow/ice is however desirable.…”

Section: Discussionsupporting

confidence: 63%

“…The effect of black carbon on snow and ice albedo is not accounted for in this version of the model, so this paper only focuses on the atmospheric forcing of aerosols. Given that the impacts of radiative forcing from black carbon (BC) in snow over the last few decades are very small compared to impacts caused by changes in greenhouse gas and other aerosol radiative forcings [ Boucher et al , ; Namazi et al , ], despite large changes in BC deposition on snow over this time period, we do not expect the exclusion of the effect of BC deposition in the CanESM2 parameterization to substantially affect the results of our study. Lastly, the 1850–2000 aerosol ERF for CanESM2 is −0.9 W/m 2 , which lies close to the middle of the range found in the CMIP5 models (ensemble mean of −1.1 W/m 2 with a standard deviation of 0.3 W/m 2 ) and is consistent with the best estimate of −0.9 W/m 2 reported in the last assessment report of the Intergovernmental Panel on Climate Change (IPCC) [ Boucher et al , ].…”

Section: Model and Simulationsmentioning

confidence: 99%

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Impact of aerosol emission controls on future Arctic sea ice cover

Gagné

Gillett

Fyfe

2015

Geophys. Res. Lett.

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We examine the response of Arctic sea ice to projected aerosol and aerosol precursor emission changes under the Representative Concentration Pathway (RCP) scenarios in simulations of the Canadian Earth System Model. The overall decrease in aerosol loading causes a warming, largest over the Arctic, which leads to an annual mean reduction in sea ice extent of approximately 1 million km2 over the 21st century in all RCP scenarios. This accounts for approximately 25% of the simulated reduction in sea ice extent in RCP 4.5, and 40% of the reduction in RCP 2.5. In RCP 4.5, the Arctic ocean is projected to become ice‐free during summertime in 2045, but it does not become ice‐free until 2057 in simulations with aerosol precursor emissions held fixed at 2000 values. Thus, while reductions in aerosol emissions have significant health and environmental benefits, their substantial contribution to projected Arctic climate change should not be overlooked.

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Section: Discussionsupporting

confidence: 63%

Section: Model and Simulationsmentioning

confidence: 99%

Impact of aerosol emission controls on future Arctic sea ice cover

Gagné

Gillett

Fyfe

2015

Geophys. Res. Lett.

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“…Brock et al, 2011). Deposition of BC onto snow and ice can reduce surface albedo and enhance light absorption by snow and ice (Wiscombe and Warren, 1980;Chýlek et al, 1983) and trigger chain reactions involving the acceleration of snow aging (Clarke and Noone, 1985;Hansen and Nazarenko, 2004), leading to accelerated melting (Quinn et al, 2008;Namazi et al, 2015). The modified local radiative balance exerted by deposited BC has the potential to further affect climate at a larger scale (Flanner et al, 2007;Doherty et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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

Martin

Morrow

et al. 2017

Atmos. Chem. Phys.

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Abstract. Black carbon (BC) contributes to Arctic warming, yet sources of Arctic BC and their geographic contributions remain uncertain. We interpret a series of recent airborne (NETCARE 2015; PAMARCMiP 2009 and 2011 campaigns) and ground-based measurements (at Alert, Barrow and Ny-Ålesund) from multiple methods (thermal, laser incandescence and light absorption) with the GEOS-Chem global chemical transport model and its adjoint to attribute the sources of Arctic BC. This is the first comparison with a chemical transport model of refractory BC (rBC) measurements at Alert. The springtime airborne measurements performed by the NETCARE campaign in 2015 and the PAMARCMiP campaigns in 2009 and 2011 offer BC vertical profiles extending to above 6 km across the Arctic and include profiles above Arctic ground monitoring stations. Our simulations with the addition of seasonally varying domestic heating and of gas flaring emissions are consistent with ground-based measurements of BC concentrations at Alert and Barrow in winter and spring (rRMSE < 13 %) and with airborne measurements of the BC vertical profile across the Arctic (rRMSE = 17 %) except for an underestimation in the middle troposphere (500-700 hPa).Sensitivity simulations suggest that anthropogenic emissions in eastern and southern Asia have the largest effect on the Arctic BC column burden both in spring (56 %) and annually (37 %), with the largest contribution in the middle troposphere (400-700 hPa). Anthropogenic emissions from northern Asia contribute considerable BC (27 % in spring and 43 % annually) to the lower troposphere (below 900 hPa). Biomass burning contributes 20 % to the Arctic BC column annually.At the Arctic surface, anthropogenic emissions from northern Asia (40-45 %) and eastern and southern Asia (20-40 %) are the largest BC contributors in winter and spring, followed by Europe (16-36 %). Biomass burning from North America is the most important contributor to all stations in summer, especially at Barrow.Our adjoint simulations indicate pronounced spatial heterogeneity in the contribution of emissions to the Arctic BC column concentrations, with noteworthy contributions from emissions in eastern China (15 %) and western Siberia (6.5 %). Although uncertain, gas flaring emissions from oilfields in western Siberia could have a striking impact (13 %) on Arctic BC loadings in January, comparable to the total influence of continental Europe and North America (6.5 % each in January). Emissions from as far as the Indo-Gangetic Plain could have a substantial influence (6.3 % annually) on Arctic BC as well.

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“…The snow-albedo effect of BC in the Arctic has since received wide attention. Numerous studies have examined the snow-albedo change in this region due to BC deposition (Jacobson, 2004;Marks and King, 2013;Namazi et al, 2015;Tedesco et al, 2016) and estimated the associated surface BC snow-albedo radiative forcing to be substantial (0.024-0.39 W m −2 ) in the Arctic (Bond et al, 2013, and references therein;Flanner, 2013;Jiao et al, 2014;Namazi et al, 2015), comparable to the forcing of tropospheric ozone in springtime Arctic (0.34 W m −2 , Quinn et al, 2008). BC deposited on snow and ice is likely to be an important reason for unexpectedly rapid sea-ice shrinkage in the Arctic (Koch et al, 2009;Goldenson et al, 2012;Stroeve et al, 2012).…”

mentioning

confidence: 99%

Factors controlling black carbon distribution in the Arctic

Liu¹,

Li²,

et al. 2017

Atmos. Chem. Phys.

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Abstract. We investigate the sensitivity of black carbon (BC) in the Arctic, including BC concentration in snow (BC snow , ng g −1 ) and surface air (BC air , ng m −3 ), as well as emissions, dry deposition, and wet scavenging using the global threedimensional (3-D) chemical transport model (CTM) GEOSChem. We find that the model underestimates BC snow in the Arctic by 40 % on average (median = 11.8 ng g −1 ). Natural gas flaring substantially increases total BC emissions in the Arctic (by ∼ 70 %). The flaring emissions lead to up to 49 % increases (0.1-8.5 ng g −1 ) in Arctic BC snow , dramatically improving model comparison with observations (50 % reduction in discrepancy) near flaring source regions (the western side of the extreme north of Russia). Ample observations suggest that BC dry deposition velocities over snow and ice in current CTMs (0.03 cm s −1 in the GEOS-Chem) are too small. We apply the resistance-in-series method to compute a dry deposition velocity (v d ) that varies with local meteorological and surface conditions. The resulting velocity is significantly larger and varies by a factor of 8 in the Arctic (0.03-0.24 cm s −1 ), which increases the fraction of dry to total BC deposition (16 to 25 %) yet leaves the total BC deposition and BC snow in the Arctic unchanged. This is largely explained by the offsetting higher dry and lower wet deposition fluxes. Additionally, we account for the effect of the Wegener-Bergeron-Findeisen (WBF) process in mixed-phase clouds, which releases BC particles from condensed phases (water drops and ice crystals) back to the interstitial air and thereby substantially reduces the scavenging efficiency of clouds for BC (by 43-76 % in the Arctic). The resulting BC snow is up to 80 % higher, BC loading is considerably larger (from 0.25 to 0.43 mg m −2 ), and BC lifetime is markedly prolonged (from 9 to 16 days) in the Arctic. Overall, flaring emissions increase BC air in the Arctic (by ∼ 20 ng m −3 ), the updated v d more than halves BC air (by ∼ 20 ng m −3 ), and the WBF effect increases BC air by 25-70 % during winter and early spring. The resulting model simulation of BC snow is substantially improved (within 10 % of the observations) and the discrepancies of BC air are much smaller during the snow season at Barrow, Alert, and Summit (from −67-−47 % to −46-3 %). Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g., the emission factors, temporal, and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds. In addition, we find that the poorly constrained precipitation in the Arctic may introduce large uncertainties in estimating BC snow . Doubling precipitation introduces a positive bias approximately as large as the overall effects of flaring emissions and the WBF effect; halving precipitation produces a similarly large negative bias.

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Simulation of black carbon in snow and its climate impact in the Canadian Global Climate Model

Cited by 26 publications

References 79 publications

Impact of aerosol emission controls on future Arctic sea ice cover

Impact of aerosol emission controls on future Arctic sea ice cover

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

Factors controlling black carbon distribution in the Arctic

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