The poleward shift of storm tracks under global warming: A Lagrangian perspective

Comprehensive models of climate change projections have shown that the latitudinal band of extratropical storms will likely shift poleward under global warming. Here we study this poleward shift from a Lagrangian storm perspective, through simulations with an idealized general circulation model. By employing a feature tracking technique to identify the storms, we demonstrate that the poleward motion of individual cyclones increases with increasing global mean temperature. A potential vorticity tendency analysis of the cyclone composites highlights two leading mechanisms responsible for enhanced poleward motion: nonlinear horizontal advection and diabatic heating associated with latent heat release. Our results imply that for a 4 K rise in the global mean surface temperature, the mean poleward displacement of cyclones increases by about 0.85 degrees of latitude, and this occurs in addition to a poleward shift of about 0.6 degrees in their mean genesis latitude. Changes in cyclone tracks may have a significant impact on midlatitude climate, especially in localized storm tracks such as the Atlantic and Pacific storm tracks, which may exhibit a more poleward deflected shape.