Fisher, Jenny A. and Jacob, Daniel J. and Wang, Qiaoqiao and Bahreini, Roya and Carouge, Claire C. and Cubison, Michael J. and Dibb, Jack E. and Diehl, Thomas and Jimenez, Jose L. and Leibensperger, Eric M. and Lu, Zifeng and Meinders, Marcel B. J. and Pye, Havala O. T. and Quinn, Patricia K. and Sharma, Sangeeta and Streets, David G. and van Donkelaar, Aaron and Yantosca, Robert M. (2011) Sources, distribution, and acidity of sulfate-ammonium aerosol in the Arctic in winter-spring. Atmospheric Environment, 45 (39). pp. 7301-7318. ISSN 1352-2310 http://resolver.caltech.edu/CaltechAUTHORS:20120130-152256716
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We use GEOS-Chem chemical transport model simulations of sulfate-ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter-spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH^(+)_(4)]/(2[SO^(2-)_(4)] + [NO^(-)_(3)]) of 0.5 mol mol^(-1) below 2 km and 0.7 mol mol^(-1) above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.
|Additional Information:||© 2011 Elsevier Ltd. Received 25 January 2011; Received in revised form 9 August 2011; Accepted 10 August 2011. This work was supported by the NASA Tropospheric Chemistry Program and the Decadal and Regional Climate Prediction using Earth System Models (EaSM) Program of the U. S. National Science Foundation. We thank A. M. Middlebrook for obtaining the ARCPAC AMS data.|
|Subject Keywords:||Arctic; Aerosol acidity; Sulfate; Ammonium; Pollution sources|
|Official Citation:||Jenny A. Fisher, Daniel J. Jacob, Qiaoqiao Wang, Roya Bahreini, Claire C. Carouge, Michael J. Cubison, Jack E. Dibb, Thomas Diehl, Jose L. Jimenez, Eric M. Leibensperger, Zifeng Lu, Marcel B.J. Meinders, Havala O.T. Pye, Patricia K. Quinn, Sangeeta Sharma, David G. Streets, Aaron van Donkelaar, Robert M. Yantosca, Sources, distribution, and acidity of sulfate–ammonium aerosol in the Arctic in winter–spring, Atmospheric Environment, Volume 45, Issue 39, December 2011, Pages 7301-7318, ISSN 1352-2310, 10.1016/j.atmosenv.2011.08.030.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||31 Jan 2012 18:13|
|Last Modified:||31 Jan 2012 18:13|
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