Pacific Decadal Oscillation Modulates the Impacts of Bering Sea Ice Loss on North American Temperature

Abstract

The cold surges have frequently attacked North America (NA) in recent decades, which has been tied to the diminished sea-ice over the Bering Sea. However, we find that the contribution of sea-ice loss to NA winter coldness is state-dependent on the Pacific Decadal Oscillation (PDO) phase. Using observations and CAM6 model simulations, we find that the phase regulates the atmospheric response to Bering ice loss. During the negative PDO phase (PDO−), there is an apparent eastward-propagating wave train, accompanied by a strengthened Alaskan ridge and NA cold high, resulting in a robust cold over Central NA. Meanwhile, enhanced upward-propagating planetary waves weaken the stratospheric polar vortex over the Pacific-NA regions. During the positive phase (PDO+), the NA temperature response to Bering ice loss is quite weak or even warm. We speculate that more NA cold extremes will appear as the PDO− continues and less as the PDO− shifts to PDO+.