Heating Rate of Light-Absorbing Aerosols from Midlatitudes to the Arctic: Implications for Arctic Warming and Northward Energy Transport

Arctic surface temperatures have increased much faster than the global mean, leading to Arctic amplification; the role of light-absorbing aerosols (LAAs; especially black carbon) in this amplification remains poorly constrained by observations. In this study, ship-borne measurements of LAAs heating rate (HR) from four research cruises between Europe and the Arctic were combined with reanalysis data (MERRA-2) determining a reanalysis HR field driving climate model simulations (CESM2). The aim was to assess how the meridional gradients in LAAs HR can influence Arctic warming by modulating atmospheric energy transport. LAAs HR declined from 335.5 ± 6.6 mK d−1 in summer and 254.0 ± 17.4 mK d−1 in winter, near Europe, to 0.9 ± 0.1 mK d−1 in summer, with zero HR inferred under polar-night conditions in winter. This gradient creates more than two orders of magnitude of atmospheric power surplus between midlatitudes and the Arctic, enhancing the poleward atmospheric meridional heat transport by 7 ± 2 and 5 ± 1 TW (summer and winter; CESM2 results). An Arctic-to-global temperature response ratio of 1.1 emerged in summer and was not meaningfully defined in winter, as the global-mean temperature response was statistically indistinguishable from zero, while the Arctic response remained positive due to the remote effect of LAAs.