Role of atmospheric rivers in shaping long term Arctic moisture variability

Atmospheric rivers (ARs) reaching high-latitudes in summer contribute to the majority of climatological poleward water vapor transport into the Arctic. This transport has exhibited long term changes over the past decades, which cannot be entirely explained by anthropogenic forcing according to ensemble model responses. Here, through observational analyses and model experiments in which winds are adjusted to match observations, we demonstrate that low-frequency, large-scale circulation changes in the Arctic play a decisive role in regulating AR activity and thus inducing the recent upsurge of this activity in the region. It is estimated that the trend in summertime AR activity may contribute to 36% of the increasing trend of atmospheric summer moisture over the entire Arctic since 1979 and account for over half of the humidity trends in certain areas experiencing significant recent warming, such as western Greenland, northern Europe, and eastern Siberia. This indicates that AR activity, mostly driven by strong synoptic weather systems often regarded as stochastic, may serve as a vital mechanism in regulating long term moisture variability in the Arctic. Arctic surface air temperatures have shown a warming trend at a rate more than twice that of the global average in recent decades, attributed to various Arctic Amplification (AA) processes driven by both anthropogenic and natural climate forcing10-13. As constrained by the Clausius-Clapeyron (CC) relationship, Arctic atmospheric warming also leads to atmospheric moistening, resulting in higher specific humidity, greater cloud cover and cloud water content, and more precipitation across the Arctic10-13. This moisture increase has substantially altered the Arctic hydrological and cryospheric variability over the past few decades14,15, owing to various moisture-related positive feedbacks connected to changing radiative properties of the atmosphere, clouds, and surface conditions. This increase in moisture is prominent throughout the year, with the most significant rise occurring during the summer months

Zhibiao Wang, Qinghua Ding, Renguang Wu, Thomas J. Ballinger, Bin Guan, Deniz Bozkurt, Deanna Nash, Ian Baxter, Dániel Topál, Zhe Li, Gang Huang, Wen Chen, Shangfeng Chen, Xi Cao, Zhang Chen