Influence of warm and moist air intrusions on black carbon deposition and snowmelt in the central Arctic

In the central Arctic, warm and moist air intrusions (WAMIs) are increasingly prevalent during winter and spring, significantly affecting the near-surface energy budget. Here, we combine in situ observations from the 2019–2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition with model simulations to investigate the role of WAMIs in transporting pollutants and enhancing black carbon (BC) wet deposition. Several WAMI episodes were associated with elevated ambient BC concentrations, and the model indicates that these events lead to an average of approximately 40% increase in BC wet deposition compared to typical winter–spring conditions. To assess the potential implications of this deposition for the cryosphere, we performed a set of sensitivity experiments using the SURFEX/ISBA-Crocus multilayer snowpack model. These experiments allowed isolating the impact of enhanced BC deposition, indicating that WAMI-driven inputs can increase solar energy absorption by 3–5 W/m2 on average and accelerate snowmelt rates by more than 20% during the following summer. These simulations offer process-based insights on the influence of episodic pollution transport events on snow and climate feedbacks. These findings underscore the need for targeted and spatially distributed measurements of BC in central Arctic snowpacks—away from potential local contamination sources (e.g., ship exhaust)—to better constrain the role of WAMIs in Arctic snow and climate processes.