Prolonged Effect of the Stratospheric Pathway in Linking Barents-Kara Sea Sea Ice Variability to the Midlatitude Circulation in a Simplified Model

To better understand the dynamical mechanism that accounts for the lead-lag correlation between early winter Barents-Kara Sea (BKS) sea ice variability and later winter midlatitude circulation response, a series of simplified atmospheric general circulation model (AGCM) experiments is conducted with a prescribed idealized near-surface heating over the BKS. A prolonged effect is found in the idealized experiments and can be attributed to the stratospheric pathway and the longer time scale in the stratosphere. The analysis of Eliassen-Palm (EP) flux shows that, as a result of the imposed heating and linear constructive interference, anomalous upward propagating planetary-scale waves are excited and weaken the stratospheric polar vortex. The response in the stratosphere persists for about 1-2 months and migrates downward to the troposphere and the surface, amplifying and lenthening the low-level jet deceleration at the midlatitudes. The stratospheric pathway is also found to amplify the cold air mass over Eurasia.