Long-Lived Sub-Micron Desert Dusts are Important Ice-Nucleating Particles in the Polar Regions

Ice-nucleating particles (INPs) modify the distribution and radiative properties of mixed-phase clouds, making them a key component of the climate system. However, we have a very limited understanding of INPs, particularly in polar regions that are remote from major low-latitude sources. In this global model study, we find that mineral dust particles persisting in the atmosphere for over 60 days still make a substantial contribution to INP concentrations in remote regions. These long-lived dust particles contribute approximately 22% of the global annual mean dust INPs, with 17% in the Arctic and 54% in the Southern Ocean. While the total dust mass, dominated by large particles, declines rapidly after emission and is rarely relevant to the radiative budget at high latitudes, the INP population remains strongly influenced by a pervasive background of small dust particles, which remain relevant for cloud phase and radiative properties long after emission.