Prolonged effect of the stratospheric pathway in linking Barents–Kara Sea sea ice variability to the midlatitude circulation in a simplified model
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To better understand the dynamical mechanism that accounts for the observed lead-lag correlation between the early winter Barents–Kara Sea (BKS) sea ice variability and the later winter midlatitude circulation response, a series of experiments are conducted using a simplified atmospheric general circulation model with a prescribed idealized near-surface heating over the BKS. A prolonged effect is found in the idealized experiments following the near-surface heating and can be explicitly attributed to the stratospheric pathway and the long time scale in the stratosphere. The analysis of the Eliassen-Palm 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. This stratospheric response persists for approximately 1–2 months accompanied by downward migration to the troposphere and the surface. This downward migration largely amplifies and extends the low-level jet deceleration in the midlatitudes and cold air advection over central Asia. The idealized model experiments also suggest that the BKS region is the most effective in affecting the midlatitude circulation than other regions over the Arctic.
KeywordsStratosphere–troposphere coupling Nudging method Planetary-scale wave propagation Barents–Kara Sea sea ice Midlatitude low-level jet Cold advection over central Asia
The authors thank Dr. Linjiong Zhou at GFDL for model stability testing and Dr. Yueyue Yu at Florida State University for discussion. PZ and YW are supported by the U.S. National Science Foundation (NSF) Climate and Large-Scale Dynamics program under Grant AGS-1406962 and a start-up fund from the Department of Earth, Atmospheric, and Planetary Sciences at Purdue University. KLS is funded by the NSF Office of Polar Programs, Arctic Research Opportunities, PLR-1603350.
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