We examine the midlatitude jet stream responses to projected Antarctic and Arctic sea‐ice loss and global ocean warming in coordinated multi‐model experiments from the Polar Amplification Model Intercomparison Project. Antarctic and Arctic sea‐ice loss cause an equatorward shift of the winter jet stream in the southern and northern hemisphere, respectively, on average across the models. Models with stronger eddy feedback simulate farther equatorward jet shifts in response to both Antarctic and Arctic sea‐ice loss. The models simulate too weak eddy feedback compared to the real world, particularly in the northern hemisphere, resulting in an underestimation of the boreal jet response to Arctic sea‐ice loss. More precise estimates of the jet shifts are obtained by using the observed eddy feedback as a constraint and suggest that the equatorward jet shifts in response to Antarctic and Arctic sea‐ice loss exceed in magnitude the simulated poleward shifts due to ocean warming.

The influence of the Atlantic Multidecadal Variability (AMV) on the North Atlantic storm track and eddy–driven jet in the winter season is assessed via a coordinated analysis of idealised simulations with state-of-the-art coupled models. Data used are obtained from a multi-model ensemble of AMV± experiments conducted in the framework of the Decadal Climate Prediction Project component C. These experiments are performed by nudging the surface of the Atlantic ocean to states defined by the superimposition of observed AMV± anomalies onto the model climatology. A robust extra-tropical response is found in the form of a wave-train extending from the Pacific to the Nordic seas. In the warm phase of the AMV compared to cold phase, the Atlantic storm track is typically contracted and less extended poleward and the low-level jet is shifted towards the equator in the Eastern Atlantic. Despite some robust features, the picture of an uncertain and model-dependent response of the Atlantic jet emerges and we demonstrate a link between model bias and the character of the jet response.

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