The goal of MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) is to improve the understanding of coupled atmosphere-ice-ocean- ecosystem processes in the Central Arctic in order to support improved sea ice and regional weather forecasting as well as climate predictions. Activities within MOSAIC include ship-borne measurements on the RV Polarstern and airborne observations, e.g. with the AWI research aircraft.

This study presents long-term observations of aerosol size distributions for both coarse and fine modes as well as of aerosol light scattering and light absorption that are ongoing at the Polar Environment Atmospheric Research Laboratory (PEARL) in the Canadian High Arctic (80N, 86W). A variety of optical poperties are determined including the aerosol single scattering albedo and the scattering angstrom exponent for 405 and 870 nm as well as the black carbon concentration.

Model simulations of an intensive field campaign conducted over the Canadian high Arctic during the summer of 2014 were carried out using an online regional air quality model (GEM-MACH). Model results were compared with in-situ measurements from multiple platforms. The model captured the regional sources and transport to the Canadian Arctic well; the vertical structure of the lower atmosphere was well simulated by the model.

Aerosol surface data is nonexistent in the main river valleys of Interior Alaska. Baseline aerosol and meteorological surface data is vital for human health, prosperity, and ecosystem preservation in a rapidly changing world. A high concentration of aerosols, of diameter ≤ 2.5 micrometer, is linked to respiratory illnesses and contributes to health care costs. In Alaska, that includes air travel by charter. A system of aerosol monitors and meteorological ground stations are being placed and managed by the Tribes in four Yukon Flats villages.

Black carbon (BC) concentrations observed in 22 snowpits sampled in the northwest sector of theGreenland Ice Sheet in April, 2014 have allowed us to identify a strong and widespread BC aerosol deposition event, which was dated to have accumulated in the pits from two snow storms between 27 July and 2 August, 2013. This event comprises a significant portion (57% on average across all pits) of total BC deposition over 10 months (July, 2013 – April, 2014).

A decrease in precipitation during winter allows polluted air parcels from mid-latitudes to reach the Arctic. Low vertical mixing in the region concentrates aerosols and decreases scavenging. Aerosol impacts on cloud microphysical parameters remain poorly understood. However, cloud properties and pollution concentrations also vary with meteorological state, which poses the challenge of how to disentangle the impact of aerosols on clouds from that of natural thermodynamic variability.

In 1990 the predecessor to the Department of Environmental Science, Aarhus University initiated the first measuring activities at Station Nord, located in the Northern part of Greenland (81°36'N 16°40' W). The first activities were carried out in a small hut containing long-wave equipment, but in 1995 it was moved to a new hut, Flygers Hut. Finally in 2015 the activities moved to a new large research infrastructure, the Villum Research Station, Station Nord (VRS).

Emissions from ships inside Arctic are an important source of the Arctic pollution as e.g. SO2, NOx and Black Carbon (BC). In an earlier work, see Winther et al (2014), a first estimate of detailed emissions inventories for BC, NOx and SO2 was presented, where the emissions were estimated by using satellite sampled AIS data for one particular year 2012 combined with ship engine power functions and technology stratified emission factors.

Using a combination of observations, lab studies and modelling we have developed an Icelandic dust storm emission inventory for climate models. Here we present results from a global modelling study quantifying the contribution of Icelandic dust in 2001 (a ‘moderate’ year with ~5Tg dust emitted) to high-latitude: ice nucleating particles (INP), cloud condensation nuclei (CCN), PM_2.5, AOD and ‘dark’ particulate deposition. Our results suggest that Icelandic dust storms do not add significantly to high-latitude CCN.

A new PACES-coordinated modeling/measurement project focused on reducing errors in model descriptions of pollutant transport, wet removal, and chemistry at mid- and high-latitudes is being developed. This project, IMPAACT (Investigation of Multiscale Processes Affecting Atmospheric Chemical Transport) will examine the transport and evolution of aerosol and gas-phase pollutants originating in East Asia and exported to the Arctic and North America.