North Pacific zonal wind response to sea ice loss in the Polar Amplification Model Intercomparison Project and its downs
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North Pacific zonal wind response to sea ice loss in the Polar Amplification Model Intercomparison Project and its downstream implications Bryn Ronalds1 · Elizabeth A. Barnes1 · Rosie Eade2 · Yannick Peings3 · Michael Sigmond4 Received: 3 March 2020 / Accepted: 22 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 preindustrial 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. Keywords Atmospheric circulation · Arctic amplification · Jet stream variability
1 Introduction Many recent studies have examined the impacts of Arctic warming and sea ice loss on both the Northern Hemisphere large scale circulation (e.g. Ronalds et al. 2018; Screen et al. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05352-w) contains supplementary material, which is available to authorized users.
2018a, b; Zappa et al. 2018; Blackport and Screen 2019; Ronalds and Barnes 2019) and midlatitude weather regimes (e.g. Sellevold et al. 2016; Cohen et al. 2018; Overland and Wang 2018a, b; Li and Luo 2019). Much of the work looking at the midlatitude eddy-driven jet streams has shown that, both in the zonal mean and over the North Atlantic basin, the eddy-driven jet stream weakens and shifts equatorward in response to Arctic amplification (e.g. Screen et al. 2018b). Recent work by Ronalds and Barnes (2019), however,
* Bryn Ronalds [email protected]
1
Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
Elizabeth A. Barnes [email protected]
2
MetOffice Hadley Centre, Exeter, Devon
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