How does extratropical warming affect ENSO?

Idealized experiments in a coupled climate model show that the remote impact of the extratropics on the tropics can modulate the behavior of El Nino-Southern Oscillation (ENSO) phenomenon. An extratropical warming can weaken the Hadley cells and slow down the shallow meridional overturning circulations in the upper Pacific, causing reductions in the equatorward cold water supply and the equatorial upwelling and thus a weakened stratification of the equatorial thermocline. Therefore, weaker and longer ENSO cycle would occur in the stabilized equatorial coupled system resulted from the extratropical warming.