A Possible Linkage between Arctic Sea-ice Loss and Stratospheric Polar Vortex

The abrupt retreat of Arctic sea-ice in recent several decades and associated atmospheric circulation changes are debating issue. In particular, what brings a lagged connection between sea-ice and atmospheric circulation remains unclear. In this study, we propose that Arctic sea-ice loss in autumn (October-December) has likely affected stratospheric polar vortex and temperature in winter (January-March). During recent two decades a large-scale wave pattern has emerged in mid-troposphere in autumn, which is characterized by anomalous high centered over Eastern Europe and elongated low along the wave-guide of polar jet. At the same time, stratospheric polar vortex in subsequent winter has weakened substantially. Statistical analysis shows that both of these trends are significantly correlated with the Arctic sea-ice melting in autumn. With a simple linear model experiment, it is shown that the enhanced diabatic heating due to the sea-ice melting can generate a similar large-scale wave as observed. Furthermore, this wave pattern highly projects onto the climatological wave-number 1 stationary wave, driving stronger planetary-scale wave propagation from the troposphere to the stratosphere through constructive wave interference. The resulting stratospheric change might contribute to the weakening of stratospheric polar vortex during last two decades. Although more quantitative investigations are needed, this result suggests that Arctic sea-ice change might play a broader role in global climate change than what is currently thought of.