Aircraft ice-nucleating particle and aerosol composition measurements in the western North American Arctic

Abstract

Abstract. Knowledge of the temperature-dependent concentration of ice-nucleating particles (INPs) is crucial to understanding the properties of mixed-phase clouds. However, the sources, transport and removal of INPs around the globe, and particularly in the Arctic region, are poorly understood. In the Arctic winter and spring, when many local sources are covered by ice and snow, it is not clear which INP types are important. In this study, we present a new dataset of aircraft-based immersion mode INP measurements and aerosol size-resolved composition in the western North American Arctic from 11 to 21 March 2018. Aerosol samples were collected between ∼ 70 and 600 m above the surface on filters that were analysed using both a freezing droplet-based assay and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The measured INP concentrations were at or close to the limit of detection, with concentrations at −20 ∘C of 1 L−1 or below. The size-resolved composition measurements indicates that the aerosol concentrations were low, dominated mostly by sea spray aerosol and mineral dust. Further analysis shows that mineral dust is important for the ice-nucleating properties of our samples, dominating over the sea spray aerosol particles in the four cases we analysed, suggesting that mineral dust is a relevant type of INP in the Alaskan springtime Arctic. Furthermore, the INP concentrations are more consistent with fertile soil dusts that have an ice-active biological component than what would be expected for the ice-active mineral K-feldspar alone. While we cannot rule out local high-latitude sources of dust, the relatively small size of the mineral dust implies that the dust was from distant sources.

Vertical distribution of ice nucleating particles over the boreal forest of Hyytiälä, Finland

“…INPs from different sources may exhibit distinct ice nucleation activities due to differences in their chemical compositions, sizes, phases, and morphologies (Kanji et al, 2017). For example, desert dust is one of the most important sources of atmospheric INPs active at temperatures below -15 °C (Hoose and Möhler, 2012;Vergara-Temprado et al, 2017;Kanji et al, 2017;Sanchez-Marroquin et al, 2023). Biological aerosols are considered another widely present type of INPs (O′Sullivan et al, 2015;O'Sullivan et al, 2018;Wex et al, 2019;Dreischmeier et al, 2017;Morris et al, 2004), and they can form ice at relatively higher temperatures than dust, although their global emissions are lower (Després et al, 2012).…”