Multi-Seasonal Measurements of the Ground-Level Atmospheric Ice-Nucleating Particle Abundance in the North Slope of Alaska

Atmospheric ice-nucleating particles (INPs) are an important subset of aerosol particles that promote the heterogeneous formation of ice crystals under ice-supersaturated conditions. In the Arctic, INPs contribute to partitioning between ice and liquid water in mixed-phase clouds, influencing cloud albedo. INPs can also catalyze precipitation and act as cloud-destroying agents in the Arctic, and accordingly, model studies suggest a high sensitivity of cloud lifetime to INP concentrations. The increase in INPs may overall result in accelerated positive radiative feedback globally. The number of Arctic INP studies investigating specific INP episodes or sources has increased in a relatively short span of time. However, there are few long-term datasets, which are needed to determine the abundance and variability of ambient Arctic INPs. Continuous INP data will benefit many researchers in the aerosol-cloud interaction research community, for example, to verify and/or improve the modeling simulation performance. Here we present one of the first long-duration INP data sets for the Arctic, 2 years of INP concentrations (n_INP) measured continuously at the Barrow Atmospheric Baseline Observatory in North Slope of Alaska (BRW-NSA). A portable ice nucleation experiment chamber (PINE-03), which simulates adiabatic expansion cooling, was used to directly monitor the ground-level INP abundance with an approximately 12-minute time resolution from October 2021 to December 2023. We document PINE-03-measured n_INP data over a wide range of heterogeneous freezing temperatures from -16 °C to -31 °C. Complementary aerosol and meteorological data analyses were performed to assess the correlation between ambient INP propensity, air mass source region, and meteorological variability in NSA. Our findings suggest (1) very high freezing efficiency of INPs across the measured temperatures as compared to the previous mid-latitude INP measurements by the same apparatus, (2) surprisingly consistent n_INP above -21 °C throughout the year that were not measured before, and (3) higher n_INP in spring than other seasons, possibly facilitated by the Arctic haze episodes.