Overview paper: new insights into aerosol and climate in the Arctic

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Abbatt, JPD, Leaitch, WR, Aliabadi, AA, Bertram, AK, Blanchet, J-P, Boivin-Rioux, A, Bozem, H, Burkart, J, Chang, RYW, Charette, J, Chaubey, JP, Christensen, RJ, Cirisan, A, Collins, DB, Croft, B, Dionne, J, Evans, GJ, Fletcher, CG, Gali, M, Ghahremaninezhad, R, Girard, E, Gong, W, Gosselin, M, Gourdal, M, Hanna, SJ, Hayashida, H, Herber, AB, Hesaraki, S, Hoor, P, Huang, L, Hussherr, R, Irish, VE, Keita, SA, Kodros, JK, Kollner, F, Kolonjari, F, Kunkel, D, Ladino, LA, Law, K, Levasseur, M, Libois, Q, Liggio, J, Lizotte, M, Macdonald, KM, Mahmood, R, Martin, RV, Mason, RH, Miller, LA, Moravek, A, Mortenson, E, Mungall, EL, Murphy, JG, Namazi, M, Norman, A-L, O'Neill, NT, Pierce, JR, Russell, LM, Schneider, J, Schulz, H, Sharma, S, Si, M, Staebler, RM, Steiner, NS, Thomas, JL, von Salzen, K, Wentzell, JJB, Willis, MD, Wentworth, GR, Xu, J-W, Yakobi-Hancock, JD
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2019
• Subjects: Earth Sciences; Oceanography; Biological Oceanography; Arctic; Canadian Arctic Archipelago; Nunavut; Arctic Archipelago; Tundra
• Online Access: https://doi.org/10.5194/acp-19-2527-2019; http://ecite.utas.edu.au/141009

Motivated by the need to predict how the Arctic atmosphere willchange in a warming world, this article summarizes recent advances made bythe research consortium NETCARE (Network on Climate and Aerosols: AddressingKey Uncertainties in Remote Canadian Environments) that contribute to ourfundamental understanding of Arctic aerosol particles as they relate toclimate forcing. The overall goal of NETCARE research has been to use aninterdisciplinary approach encompassing extensive field observations and arange of chemical transport, earth system, and biogeochemical models. Severalmajor findings and advances have emerged from NETCARE since its formation in2013. (1)Unexpectedly high summertime dimethyl sulfide (DMS) levels wereidentified in ocean water (up to 75 nM) and the overlying atmosphere (up to1 ppbv) in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds,which are widely prevalent, were identified as an important DMS source (withDMS concentrations of up to 6 nM and a potential contribution to atmosphericDMS of 20 % in the study area). (2)Evidence of widespread particlenucleation and growth in the marine boundary layer was found in the CAA inthe summertime, with these events observed on 41 % of days in a 2016cruise. As well, at Alert, Nunavut, particles that are newly formed and grownunder conditions of minimal anthropogenic influence during the months of Julyand August are estimated to contribute 20 % to 80 % of the 3050 nmparticle number density. DMS-oxidation-driven nucleation is facilitated bythe presence of atmospheric ammonia arising from seabird-colony emissions,and potentially also from coastal regions, tundra, and biomass burning. Viaaccumulation of secondary organic aerosol (SOA), a significant fraction of the newparticles grow to sizes that are active in cloud droplet formation. Althoughthe gaseous precursors to Arctic marine SOA remain poorly defined, themeasured levels of common continental SOA precursors (isoprene andmonoterpenes) were low, whereas elevated mixing ratios of oxygenated volatileorganic compounds (OVOCs) were inferred to arise via processes involving thesea surface microlayer. (3)The variability in the vertical distribution ofblack carbon (BC) under both springtime Arctic haze and more pristinesummertime aerosol conditions was observed. Measured particle sizedistributions and mixing states were used to constrain, for the first time,calculations of aerosolclimate interactions under Arctic conditions.Aircraft- and ground-based measurements were used to better establish the BCsource regions that supply the Arctic via long-range transport mechanisms,with evidence for a dominant springtime contribution from eastern andsouthern Asia to the middle troposphere, and a major contribution fromnorthern Asia to the surface. (4)Measurements of ice nucleating particles(INPs) in the Arctic indicate that a major source of these particles ismineral dust, likely derived from local sources in the summer and long-rangetransport in the spring. In addition, INPs are abundant in the sea surfacemicrolayer in the Arctic, and possibly play a role in ice nucleation in theatmosphere when mineral dust concentrations are low. (5)Amongst multipleaerosol components, BC was observed to have the smallest effective depositionvelocities to high Arctic snow (0.03 cm s −1 ).