Long-range transport of mineral dust into the Arctic

Mineral dust is one of the most abundant aerosol types in the Arctic and it has multiple effects on the sensitive Arctic climate system. In this study, three-dimensional reanalysis datasets of atmospheric composition, CAMSRA and MERRA-2, are analyzed for the years 2003 to 2018 with the aim to assess where and when significant amounts of dust aerosols are transported into the Arctic. We also examine how the transport occurs i.e. to what degree dust is transported in distinct dust events versus more continual diffusive transport according to the reanalyses. The reanalysis data show that the largest dust mass transport into the Arctic occurs across Siberia during spring and early summer, but occasionally transport events of high impact occur across other geographical areas during various seasons. In some respects, the reanalyses show considerable differences: the transport in MERRA-2 is significantly greater, more widespread and occurs at higher altitudes than in CAMSRA. The transport in CAMSRA is to a higher degree focused to well-defined events in space and time; the integrated mass transport of the 10 most intense dust events in CAMSRA constitutes 6% of the total integrated dust transport 2003-2018, whereas the corresponding value for MERRA-2 is only 1%. The deviating results between CAMSRA and MERRA-2 could be explained by production of too coarse dust in CAMSRA in combination with an assimilation process that consequently assimilates too little dust. Additionally, MERRA-2 overestimates the production of light particles and the assimilation process increases dust concentration in remote areas. Our results underscore the difficulties of modelling such a complex process as the mineral dust transport into the Arctic; from the fundamentals to define potential dust emitting areas around the globe and the parametrization of the dust emission, to the atmospheric transport, vertical diffusion scheme and assimilation of AOD into the forecast model. However, this study gives new insights into the magnitude and spatiotemporal distribution of mineral dust transport into the Arctic.