Quantifying the Impact of Icelandic Dust Storms on High-Latitude aerosol

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. Nor can they explain the formation and persistence of summertime mixed-phase Arctic marine clouds. However, Icelandic dust storms are shown to contribute to high-latitude summertime PM_2.5 (and PM₁₀) both during and in the aftermath of dust events frequently raising PM_2.5concentrations around Iceland and S. Greenland above ~100ug/m³contributing to poor air quality. Our results also suggest that Icelandic dust storms may in the short term increase aerosol optical depth at high latitudes although significant uncertainty remains due to variations in measured refractive indices. Finally, we note that while the majority of Icelandic dust is deposited on, or in the vicinity of Iceland, deposition rates of Icelandic dust on Greenland and the European Arctic ocean are higher than BC. However, variations in refractive index (BC is significantly more light absorbent), differing deposition processes (dust is primarily dry deposited while BC is nucleation scavenged) and underestimation of Arctic BC in the model suggest further research is required to fully quantify the impact of dust deposition compared to BC in the Arctic.