[A-AS11] Atmospheric Chemistry

[AAS11-26] The effect of increased dust by warming on ice nucleation in Arctic lower tropospheric clouds

*Hitoshi MATSUI¹, Kei Kawai¹, Yutaka Tobo^2,3, Yoshinori Iizuka⁴, Sumito Matoba⁴ (1.Graduate School of Environmental Studies, Nagoya University, 2.National Institute of Polar Research, 3.Graduate Institute for Advanced Studies, SOKENDAI, 4.Institute of Low Temperature Science, Hokkaido University)

Keywords:Aerosol-cloud interactions, Ice nucleation, Arctic warming, Global model simulations, Feedback

Ice nucleating particles (INPs) affect the cloud radiative budget in the rapidly warming Arctic by changing the cloud liquid/ice phase balance. Dust emitted in the Arctic (Arctic dust) has been suggested to be a major contributor to INPs in the Arctic lower troposphere. However, how Arctic dust and its impacts on ice nucleation change with Arctic warming has not been explored. Here we use global model simulations to show that the Arctic dust emission flux increases by 20% from 1981−1990 to 2011−2020 (and by 140% in sensitivity simulations with a 4 K increase in sea surface temperature) as the surface temperature increased and snow cover fraction decreased in the Arctic. As an average over the Arctic, this increase in the Arctic dust emission flux weakens the sensitivity of ice nucleation in Arctic lower tropospheric clouds to warming by more than 40% compared to the case that does not consider Arctic dust emission increases. Regionally, the increase in ice nucleation by increasing emissions outweighs the decrease in ice nucleation by decreasing ice nucleation efficiency of INPs due to increasing temperature in more than 30% of the Arctic region, which might change the sign of the phase transition of mixed-phase clouds in the Arctic lower troposphere. Our results demonstrate a better understanding of the counterbalancing effects of Arctic dust (increasing emissions and decreasing ice nucleation efficiency) is needed for more accurate estimates of changes in ice nucleation and its impacts on mixed-phase clouds in the rapidly changing climate of the Arctic.