Dust-driven cloud phase changes may impact summertime cooling over Arctic sea ice

Cloud phase has important impacts on Arctic surface temperatures, and there is substantial circumstantial evidence that dust aerosols have strong impacts on cloud phase over the Arctic on a regional scale. We used seven years of satellite observations and model and reanalysis products to control for co-varying meteorology, and to assess how dust and other aerosols impact cloud phase over the summertime sea ice. We focus on clouds at 3 km, where dust modeling is most accurate. Dust aerosols caused about 4.5% of clouds below -15 °C to change phase, with smaller effects at higher temperatures. Sulfate has a smaller impact on cloud phase. Dust is associated with cloud-mediated surface cooling of up to a 6.3 W m-2 below single-layer clouds at ~3 km in June. Lastly, we discuss the optimal meteorological conditions for future in situ studies to maximize insight into the mechanisms driving the observed dust effects.