Impact of Dust on Climate and AMOC During the Last Glacial Maximum Simulated by CESM1.2.

While the impact of dust on climate and Atlantic Meridional Overturning Circulation (AMOC) during the interglacial period such as the mid‐Holocene has been studied extensively, its impact during the glacial period is unclear. Here we investigate how the climate and AMOC would change if there had been no dust during the Last Glacial Maximum. Model simulations show that the dust removal leads to a global cooling of over 2.4°C and a weakening of AMOC by ∼30%. Such temperature change is opposite in sign to that for the MH. The cooling is attributed to the increase of snow and ice albedo and weakening of AMOC when dust is removed, and is amplified through a positive feedback between sea ice and AMOC. Our results indicate that the climate and AMOC are more sensitive to dust change during the glacial than the interglacial period. Plain Language Summary: Dust in the atmosphere reflects and absorbs sunlight, reducing the shortwave radiation reaching the surface, while the dust deposited on snow and ice reduces the surface albedo and increases the shortwave radiation received at the surface. Our previous work (Zhang et al., 2021) showed dust reduction during the interglacial period (e.g., mid‐Holocene; MH) would cause a global warming of 0.1°C and a weakening of Atlantic Meridional Overturning Circulation (AMOC) by 6.2%. This warming was due to more sunlight received at the surface when atmospheric dust is removed. Here we show that if dust was removed during the Last Glacial Maximum (LGM), climate will be cooled significantly rather than warmed. The major reason is that snow on land was much more extensive during LGM than MH, such that the increase of snow albedo after dust removal has a dominating effect on climate. Result suggests that the global climate and AMOC in the glacial period are more sensitive to dust change than those in the interglacial period. Key Points: If there were no dust during the Last Glacial Maximum (LGM), global surface temperature would have been lower by 2.4 °CAtlantic Meridional Overturning Circulation would have been 30% weaker if there were no dust during the LGMThe ocean and sea‐ice dynamics amplify the climate impact of dust by a factor of 2 [ABSTRACT FROM AUTHOR]