Warm and moist air intrusions drive black carbon deposition and accelerate central Arctic snowmelt

In the central Arctic, warm and moist air intrusions (WAMIs) are increasingly prevalent during winter and spring, significantly impacting the near-surface energy budget. This study investigates WAMI-induced transport and wet deposition of black carbon (BC) and its subsequent influence on snow properties and melting. Using a modeling approach combined with extensive observational data from the 2019–2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, we document several episodes of elevated BC wet deposition during winter and spring (Nov–Apr). These events, driven by WAMI-transported pollution and moisture, result in an average 41% increase in BC wet deposition compared to typical winter/spring conditions. Furthermore, this enhanced BC deposition contributes to increased solar energy absorption (+3.4–4.6 W/m2 on average) and accelerated snowpack melt rate (+24–36%) during the subsequent summer. Despite their episodic occurrence (only 15% of the time), this study underscores the critical role of WAMIs in shaping the central Arctic environment and emphasizes the importance of the BC snow albedo effect. Our findings highlight the need for further investigation into the broader climatic impacts of WAMI-induced pollution transport in the Arctic.