North Pacific zonal wind response to sea ice loss in the Polar Amplification Model Intercomparison Project and its downstream implications.

Recent studies suggest that the wintertime North Pacific eddy-driven jet stream will strengthen and extend eastward in response to Arctic sea ice loss. Using output from the Polar Amplification Model Intercomparison Project we examine the mean change of the North Pacific wintertime zonal winds, and use cluster analysis to explore the change in sub-seasonal, wintertime variability in zonal winds between experiments with future Arctic sea ice concentrations relative to a pre-industrial run. Further, given the relationship between the North Pacific jet stream and North American weather regimes, we also examine the changes in surface temperature variability over North America. The four climate models investigated here exhibit robust agreement in both sign and structure of the atmospheric responses, with a strengthened wintertime North Pacific jet, an increase in anomalously strong and extended jet events, and a decreased frequency of weakened and equatorward-shifted jet events in response to reduced Arctic sea ice. The models also show changes in wintertime, North American surface temperature patterns that are consistent with the zonal wind changes seen in the North Pacific. There is an increase in the frequency of occurrence of the North American temperature dipole pattern, defined as anomalously warm temperatures in the west or northwest and anomalously cold temperatures in the east or southeast, and a decrease in the frequency of anomalously cold temperatures over North America.