Distinct Tropospheric and Stratospheric Mechanisms Linking Historical Barents‐Kara Sea‐Ice Loss and Late Winter Eurasian Temperature Variability

Abstract

AbstractReduced Arctic sea‐ice has been proposed to induce severe Eurasian cold events. However, the physical mechanisms for this connection, particularly the relative importance of tropospheric and stratospheric processes, remain unclear. Using ERA‐Interim reanalysis data and WACCM‐SC simulations, we show that the Eurasian cooling induced by reduced sea‐ice centers over eastern Asia and northern Europe. Tropospheric and stratospheric processes contribute roughly equally to the cooling over eastern Asia, while the stratospheric and tropospheric contributions are 60% and 40%, respectively, over northern Europe. In the tropospheric pathway, weakened meridional temperature gradient due to reduced sea‐ice strengthens the Ural blocking and enhances the Siberian High. The enhanced Siberian High favors two streams of cold air‐mass, reaching northern Europe and eastern Asia. In the stratospheric pathway, enhanced upward‐propagating planetary wave 1 causes a shift of the stratospheric polar vortex toward Eurasia and consequently, tropospheric cyclonic anomalies are induced that enhance surface cold anomalies.