EESS talk on "An Observation-Based Climatology of Aerosols During Warm and Moist Intrusions into the Arctic"

Arctic climate change is more pronounced than in other regions, manifesting itself through increase in surface temperatures three to four times that of the global average, a phenomenon referred to as Arctic Amplification (AA). Increased heat and moisture transport to the Arctic from lower latitudes, primarily occurring through warm and moist air intrusions, associated with abrupt increased transport of heat and moisture to the polar regions, has been shown to potentially contribute to AA. Recent studies highlight that these events are significant sources of aerosol particles in the Arctic, which can significantly influence the local climate by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INP), thereby affecting Arctic cloud properties and thus the resulting radiative forcing in the region. However, the contribution of these short-lived events to different aerosol size modes, CCN and droplet number concentrations remains unconstrained. In this study, we use long term aerosol and CCN observations, combined with back trajectory analysis and a state-of-the-art cloud droplet parameterization, to assess the contribution of warm and moist intrusion events to CCN variability, aerosol size distributions, and cloud droplet number concentrations at five Arctic sites: Zeppelin, Villum, Tiksi, Alert, and Utqiaġvik/Barrow. Our results show that intrusions are a major driver of CCN perturbations in the Arctic, especially in summer, when accumulation mode and CCN concentrations increase significantly at all sites during warm and moist intrusion events. In winter and spring, however, the response splits into two distinct regimes: at sites near 0° longitude (Zeppelin, Villum, and Alert), intrusions lead to reduced concentrations, while at sites near 180° longitude (Tiksi and Utqiaġvik/Barrow), they result in increased accumulation mode and CCN concentrations. We attribute these contrasting patterns to the balance between pollution source influence and wet scavenging along air mass trajectories. The same regimes are also reflected in simulated droplet concentrations: intrusions consistently enhance droplet concentrations at Tiksi and Utqiaġvik/Barrow year-round, whereas at Zeppelin, Villum, and Alert, lower droplet concentrations in winter and spring indicate more pristine cloud conditions.

Berkay is a PhD researcher at EPFL in the Extreme Environments Research Laboratory (EERL) and the Laboratory of Atmospheric Processes and their Impacts (LAPI), supervised by J. Schmale and A. Nenes. His work focuses on modeling aerosol–cloud interactions in the Arctic. He grew up in Istanbul, Türkiye, and earned his BSc and MSc in Meteorological Engineering and Atmospheric Sciences at Istanbul Technical University.