Increased aerosol concentrations in the High Arctic attributable to changing atmospheric transport patterns

The Arctic environment has changed profoundly in recent decades. Aerosol particles are involved in numerous feedback mechanisms in the Arctic, e.g., aerosol-cloud/radiation interactions, which have important climatic implications. To understand changes in different Arctic aerosol types and number concentrations, we have performed a trend analysis of particle number size distributions, their properties, and their associated air mass history at Villum Research Station, northeastern Greenland, from 2010 to 2018. We found that, during spring, the total/ultrafine mode number concentration and the time air masses spent over the open ocean is significantly increasing, which can be ascribed to transport patterns changing to more frequent arrival from the ice-free Greenland Sea. We found that, during summer, the total/ultrafine mode number concentration, the occurrence of the Nucleation cluster (i.e. newly formed particles from gas to particle conversion), and the time air masses spent over the open ocean is significantly increasing. This can also be attributed to changing transport patterns, here with air masses arriving more frequently from Baffin Bay. Finally, we found that, during autumn, the ultrafine number concentration and the occurrence of the Pristine cluster (i.e. clean, natural Arctic background conditions) is significantly increasing, which is likely due to increasing amounts of accumulated precipitation along the trajectory path and decreasing time air masses spent above the mixed layer, respectively. Our results demonstrate that changing circulation and precipitation patterns are the factors predominantly affecting the trends in aerosol particle number concentrations and the occurrence of different aerosol types in northeastern Greenland