Interannual Variability of Early Winter Sea Ice over the Barents-Kara Seas Due to the Quasi-Biennial Oscillation

Arctic sea ice has been declining rapidly in recent decades with a large interannual variability. While its long-term change has been extensively examined, its interannual variability is not well understood. In this study, we show that the interannual variability of early winter Arctic sea ice is partly modulated by the Quasi-Biennial Oscillation (QBO) in the tropical stratosphere. When the QBO is in an easterly phase, early winter sea ice concentrations over the Greenland and Barents Seas become anomalously low, with delayed freeze-up. This remote connection is mediated by the QBO-induced tropical convection change. During the easterly phase of the QBO in October-December, tropical convections over the Maritime Continent are enhanced while those over the Indian Ocean and the South China Sea are suppressed. These tripolar convection anomalies excite the Rossby waves that propagate into the extratropics and generate an anticyclonic circulation anomaly around the Barents-Kara Seas. The associated moisture transport into the Arctic enhances the downward infrared radiation, resulting in anomalously low sea ice concentrations over the Greenland and Barents Seas. The linear model experiments confirm the formation of an anticyclonic circulation anomaly around the Barents-Kara Seas by tropical heating anomalies. This result suggests that early winter sea ice concentrations over the Greenland and Barents Seas can be better understood and predicted by considering the QBO.