Instant and Delayed Effects of Autumn Black Carbon Aerosols Over South Asia on Arctic and Eurasian Surface Air Temperature

Black carbon (BC) aerosols can affect both local and remote long-term climate, but whether they can induce remote changes at short-term timescales is unclear. Through analyses of observations and time-slice model simulations, this study shows that South Asian autumn BC aerosols can cause instant and delayed responses of surface air temperature over the Arctic and Eurasia. In autumn, higher BC loading over South Asia leads to decreased rainfall and tropospheric diabatic cooling there. This cooling can remotely excite an anomalous anticyclone over Europe that transports warm and moist air into the Arctic to precondition sea ice melting over the Barents-Kara Seas (BKS). The consequent decrease of sea ice cover (SIC) causes BKS warming through increased surface exchange fluxes, and the concurring anomalous anticyclone near the Ural Mountains induces surface cooling over Eurasia. This temperature anomaly pattern can persist into the ensuing winter due to the continued SIC decrease across seasons.