Future changes in the wintertime ENSO-NAO teleconnection under greenhouse warming

Abstract

AbstractEl Niño-Southern Oscillation (ENSO) teleconnection to the Euro-Atlantic exhibits strong subseasonal variations, as the North Atlantic Oscillation (NAO) response systematically reverses its phase from early to late winter. Based on two sets of atmospheric model simulations in CMIP6 forced by historical and projected SST, we report a future disappearance of this teleconnection reversal, with the positive early winter ENSO-NAO correlation turning negative and the negative late winter correlation becoming stronger. We suggest that this negative NAO tendency is associated with the strengthening and eastward shift of the ENSO atmospheric teleconnection towards the Euro-Atlantic due to parallel changes in the ENSO tropical convection. While the early winter NAO phase transition is further facilitated by the mean state change in the North Atlantic jet meridional shear, which shifts the ENSO-driven Rossby wave-propagating direction, an intensified stratospheric pathway is demonstrated to play an additional role in strengthening the late winter NAO response.