What Configuration of the Atmospheric Circulation Drives Extreme Net and Total Moisture Transport Into the Arctic

Abstract

Previous work highlighted different configurations of the atmospheric circulation causing moisture transport into the Arctic and contributing to surface warming. Here, we clarify the configurations leading to extreme wintertime events of zonal-mean net and total (sum of absolute values of poleward and equatorward) moisture transports by comparing feature-based weather system diagnostics with zonal-wavenumber decomposition of moisture transport in reanalysis data. Results show that extreme Arctic moisture transport events are attributable to individual weather systems, where cyclones favor net transport and blocks favor total transport. Zonal-wavenumber decomposition reveals that net moisture transport is dominated by planetary scales (zonal-wavenumbers k ≤ 3). Comparison between the two diagnostics suggests that blocks account for planetary scale contributions to net transport by interacting with cyclones rather than driving the transport themselves. Finally, net and total moisture transport events result in Arctic surface warming via different underlying processes related to cyclones and blocks, respectively. ©2020. American Geophysical Union. All Rights Reserved.