A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation: insights from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition

[摘要] The Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline insea ice extent, which thereby enhances feedback loops in the surface energybudget in the Arctic. Arctic aerosols play an important role in theradiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study,we investigate the annual cycle in the aerosol particle number sizedistribution (PNSD), particle number concentration (PNC), and black carbon(BC) mass concentration in the central Arctic during the Multidisciplinarydrifting Observatory for the Study of Arctic Climate (MOSAiC) expedition.This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k -meanscluster analysis, FLEXPART simulations, and inverse modeling to evaluateseasonal patterns and the influence of different source regions on theArctic aerosol population. Furthermore, we compare the aerosol observationsto land-based sites across the Arctic, using both long-term measurements andobservations during the year of the MOSAiC expedition (2019–2020), toinvestigate interannual variability and to give context to the aerosolcharacteristics from within the central Arctic. Our analysis identifiesthat, overall, the central Arctic exhibits typical seasonal patterns ofaerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea icemelting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was thedominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based observatories. We also show that thewintertime Arctic Oscillation (AO) phenomenon, which was reported to achievea record-breaking positive phase during January–March 2020, explains theunusual timing and magnitude of Arctic haze across the Arctic region compared to longer-term observations. In summer, the aerosol PNCs of the nucleation and Aitken modes are enhanced; however, concentrations werenotably lower in the central Arctic over the ice pack than at land-basedsites further south. The analysis presented herein provides a currentsnapshot of Arctic aerosol processes in an environment that is characterizedby rapid changes, which will be crucial for improving climate modelpredictions, understanding linkages between different environmentalprocesses, and investigating the impacts of climate change in future Arcticaerosol studies.

[学科分类] 医学（综合）