Arctic autumn warming since 2002 dominated by changes in moisture modulated by multiple large-scale atmospheric circulations

Abstract

The clear-sky downward longwave radiation related to water vapor (LW-WV) has been confirmed to be the dominant factor promoting the autumn warming in the Arctic in the boreal autumn. In this study, we reveal the spatiotemporal characteristics of the 2 m air temperature (t2m), clear-sky downward longwave radiation (CDLW), and water vapor in the Arctic and the mechanism affecting the change in the autumn LW-WV. Since 2002, not only have the temporal variations in regional t2m, CDLW, and water vapor been synchronous at the interdecadal scale, but their largest spatial variations have also mainly been located in the Barents-Kara Sea and the Chukchi Sea. A diagnosis of the atmospheric moisture budget shows that the change in the water vapor divergence is dominated by the change in the mean circulation dynamics in the Barents-Kara Sea, while the change in the thermodynamics caused by the changes in the local specific humidity and the mean circulation dynamics are both important to the change in the water vapor divergence in the Chukchi Sea. The positive phase in the Arctic Oscillation (AO) and the Pacific/North American Pattern (PNA) have contributed to the increase in the water vapor in the Barents-Kara Sea, while the positive phase in the North Atlantic Oscillation (NAO) and the PNA are responsible for the increase in the water vapor in the Chukchi Sea. Therefore, synergetic effects of the multiple large-scale circulations play an important role in the recent warming in the Arctic in autumn.