New insights into aerosol and climate in the Arctic
Authors: Abbatt Jonathan P. D. , Leaitch W. Richard , Aliabadi Amir A. , Bertram Alan K. , Blanchet Jean-Pierre , Boivin-Rioux Aude , Bozem Heiko , Burkart Julia , Chang Rachel Y. W. , Charette Joannie , Chaubey Jai P. , Christensen Robert J. , Cirisan Ana , Collins Douglas B. , Croft Betty , Dionne Joelle , Evans Greg J. , Fletcher Christopher G. , Ghahreman Roya , Girard Eric , Gong Wanmin , Gosselin Michel , Gourdal Margaux , Hanna Sarah J. , Hayashida Hakase , Herber Andreas B. , Hesaraki Sareh , Hoor Peter , Huang Lin , Hussherr Rachel , Irish Victoria E. , Keita Setigui A. , Kodros John K. , Köllner Franziska , Kolonjari Felicia , Kunkel Daniel , Ladino Luis A. , Law Kathy , Levasseur Maurice , Libois Quentin , Liggio John , Lizotte Martine , Macdonald Katrina M. , Mahmood Rashed , Martin Randall V. , Mason Ryan H. , Miller Lisa A. , Moravek Alexander , Mortenson Eric , Mungall Emma L. , Murphy Jennifer G. , Namazi Maryam , Norman Ann-Lise , O'Neill Norman T. , Pierce Jeffrey R. , Russell Lynn M. , Schneider Johannes , Schulz Hannes , Sharma Sangeeta , Si Meng , Staebler Ralf M. , Steiner Nadja S. , Galí Martí , Thomas Jennie L. , von Salzen Knut , Wentzell Jeremy J. B. , Willis Megan D. , Wentworth Gregory R. , Xu Jun-Wei , Yakobi-Hancock Jacqueline D. 
Published: October 2018

Abstract. Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013 . (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water and the overlying atmosphere in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source. (2) Evidence was found of widespread particle nucleation and growth in the marine boundary layer in the CAA in the summertime. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from sea bird colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic material (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol–climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow.