Around 40 scientists will gather in Fairbanks, Alaska between 14-16 May 2018 for the first ALaskan Pollution and Chemical Analysis (ALPACA) project workshop ALPACA seeks to improve knowledge of atmospheric chemical mechanisms occurring under cold and dark conditions. These gaps are exacerbated by lack of knowledge of emissions and by wintertime meteorology, and a lack of measurements in regions with sub-freezing temperatures and low to absent photochemistry.

Estimation of the Siberian fire in September 2016 on BC concentration in the Bering Sea using a regional chemical transport model

 To estimate the impact of biomass burning on the concentration of BC and other pollutants, we had conducted model simulations over the Pan-Arctic region using a regional chemical transport model (WRF-Chem). The initial and lateral boundary conditions for the meteorology and chemical species were taken from NCEP-GFS and MOZART-4/GEOS-5, respectively. RACM and GOCART modules were used for the gaseous and aerosol chemistry, respectively. Anthropogenic emissions were based on EDGAR 4.3, and the biomass burning were based on the near-real-time version of FINN for each day.

Local versus remote sources of mineral dust in the Arctic - an emerging issue?

Mineral dust can have a strong radiative forcing impact in the Arctic, including its effect on snow albedo, which has seen relatively little attention compared to black carbon, despite its probably much larger importance. Global dust models focus on the main dust source regions in other parts of the world and largely ignore high-latitude dust sources. Groot Zwaaftink et al.

Historic Measurements of Arctic Air Pollution (Arctic Haze) from Barrow Observatory and the Arctic Gas and Aerosol Program (AGASP)

Air Pollution measured at the NOAA, Barrow Atmospheric Baseline Observatory (71<sup>0</sup> N, 156<sup>0</sup> W, 11 m asl) arrives predominately in easterly winds with the pollution originating in Eastern Europe and northern Russia. The pollution is highly stratified and concentrated above the Arctic marine boundary layer. As such, surface concentrations of pollution are generally much lower than those measured above the marine boundary layer (aircraft profiles).

An aerosol-climate model evaluation study in the framework of the (AC)^3 project

In the Arctic, climate warming is about twice as fast as the rest of the world. However, various feedback mechanisms that potentially play an important role are yet poorly understood. The German project &ldquo;Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms&rdquo; (AC)<sup>3 </sup>is dedicated to better quantify relevant processes and broaden the understanding of the mechanism involved with a range of field measurements and modelling. Aerosol plays an important role by modulating the Arctic energy balance.

Aerosols at the Poles: An AeroCom Phase II multi-model evaluation

The role of atmospheric aerosols in the changing Polar climate is not well understood and aerosols are poorly constrained in models. Aerosols from anthropogenic and natural sources reach the Polar Regions through long-range transport. Here we compare aerosol optical depth (AOD) from simulations with 16 global aerosol models from the AeroCom phase II model inter-comparison project with available observations at both Poles. We show that the annual mean multi-model median is representative of the observations in Arctic, but that the inter-model spread is large.

Long-term (1850-2010) trends of black carbon deposition in the European Arctic

The climate warming effect of black carbon (BC) is amplified in the Arctic due to its deposition on light surfaces, decreasing reflectivity and hastening snow and ice melt. Monitoring indicates that Arctic atmospheric BC concentrations have declined by 40 % between 1990 and 2009. However, ca. 90 % of BC is wet-deposited in the Arctic and therefore mostly not recorded by atmospheric measurements. Consequently, atmospheric BC concentration and BC deposition trends may diverge. To get a comprehensive view on the climate impact of BC in the Arctic measurements of BC deposition are essential.

Cross-polar transport and scavenging of Siberian aerosols containing black carbon during the 2012 ACCESS summer campaign

During the ACCESS airborne campaign in July 2012, extensive boreal forest fires resulted in significant aerosol transport to the Arctic. A 10 day episode combining intense biomass burning over Siberia and low-pressure systems over the Arctic Ocean resulted in efficient transport of plumes containing black carbon (BC) towards the Arctic, mostly in the upper troposphere. A combination of in situ airborne observations, satellite analysis and WRF-Chem simulations are used to understand the vertical and horizontal transport mechanisms of BC with a focus on the role of wet removal.

Coordinating interdisciplinary and international research through CATCH (The Cryosphere and ATmospheric CHemistry)

CATCH is a new international activity co-sponsored by IGAC (International Global Atmospheric Chemistry). As an emerging international activity established in 2016, the CATCH mission is to facilitate atmospheric chemistry research within the international community, with a focus on natural processes specific to cold regions of the Earth. Cryospheric processes are known to be important for atmospheric chemistry in the Polar regions as well as other cold regions, such as continental snowpack.