The Early Winter Sea Ice Variability under the Recent Arctic Climate Shift*

This study reveals that sea ice in the Barents and Kara Seas plays a crucial role in establishing a new Arctic coupled climate system. The early winter sea ice before 1998 shows double dipole patterns over the Arctic peripheral seas. This pattern, referred to as the early winter quadrupole pattern, exhibits the anticlockwise sequential sea ice anomalies propagation from theGreenland Sea to the Barents–Kara Seas and to the Bering Sea from October to December. This early winter in-phase ice variability contrasts to the out-of-phase relationship in late winter. The mean temperature advection and stationary wave heat flux divergence associated with the atmospheric zonal wave-2 pattern are responsible for the early winter in-phase pattern. Since the end of the last century, the early winter quadrupole pattern has broken down because of the rapid decline of sea ice extent in the Barents–Kara Seas. This remarkable ice retreat modifies the local ocean– atmosphere heat exchange, forcing an anomalous low air pressure over the Barents–Kara Seas. The subsequent collapse of the atmospheric zonal wave-2 pattern is likely responsible for the breakdown of the early winter sea ice quadrupole pattern after 1998. Therefore, the sea ice anomalies in the Barents–Kara Seas play a key role in establishing new atmosphere–sea ice coupled relationships in the warming Arctic.