Arctic Ice Fog: Unveiling the Role of Aerosol Chemistry

NURUN NAHAR LATA, Ismail Gultepe, Harindra Joseph Fernando, Darielle Dexheimer, Zezhen Cheng, Fan Mei, Swarup China, Pacific Northwest National Laboratory

     Abstract Number: 480
     Working Group: Aerosols, Clouds and Climate

Abstract
Arctic ice fog (IF) is a meteorological phenomenon characterized by cold air temperatures (Ta) and suspended ice crystals (<200 µm) in the lower atmosphere, reducing visibility to less than 1 km. Despite its prevalence, the effects of IF on the Arctic climate are poorly understood. IF impacts traffic, human safety, ecosystems, and local weather by reducing visibility and causing light snow (LSN) precipitation. Associated with high-latitude boundary layer mixed-phase clouds, IF's evolution and properties are poorly known. To address this gap, we conducted aerosol sampling during IF, light-blowing snow (LSN), and cloudy conditions at the U.S. Department of Energy Atmospheric Radiation Measurement Program's facility at Oliktok Point, Alaska, in the IFFExO (Ice Fog Field Experiment at Oliktok Point).

Aerosols were collected using the Size and Time-resolved Aerosol Collector (STAC) and cascade impactors on ARM's Tethered Balloon System (TBS). Samples were analyzed using multimodal microscopy and spectroscopic techniques, covering particle sizes ranging from 0.12 to 5 µm. Chemical analysis revealed variations in size-resolved composition between IF and non-IF (NIF) periods. IF samples were characterized by a higher fraction of sulfate and carbonaceous particles with lower organic volume fractions (OVF<20% and 20-40%). In contrast, LSN and cloudy/foggy samples contained more Na-rich and carbonaceous particles with higher organic volume fraction, OVF~60-80%. This suggests that ice nuclei (IN) leading to IF crystal nucleation likely originated from solid sulfate and carbonaceous particles. The physicochemical properties of IF-processed aerosols offer valuable information for IF prediction and to better evaluate the lifecycle of high-level ice clouds. This study provides critical insights into IF particle chemistry and formation mechanisms, improving our understanding of IF processes and their impacts on weather and climate simulations, and informing strategies for mitigating IF-related challenges in the Arctic region and cold climates.