To investigate the role of ENSO in regulating the timemean
thermal stratification of the equatorial Pacific,
perturbation experiments are conducted in pairs with a
coupled model. In one experiment, ENSO is turned off
while in the other experiment ENSO is kept on.
Perturbations are introduced through either enhancing
tropical heating or increasing subtropical cooling. In the
absence of ENSO, the time-mean difference between the
warm-pool SST (Tw) and the characteristic temperature of
the equatorial thermocline (Tc) responds sensitively to
either enhanced tropical heating or enhanced subtropical
cooling. In the presence of ENSO, such a sensitivity to
destabilizing forcing disappears. The lack of sensitivity in
the response of Tw-Tc is linked to a stronger ENSO in
response to the destabilizing forcing. ENSO in the model
acts as a basin-scale heat ‘‘mixer’’ that enables surface heat
to be transported to the depths of the equatorial thermocline.
The study raises the question whether models with poor
simulations of ENSO can give reliable predictions of the
response of the time-mean climate to global warming.
Citation: Sun, D.-Z., and T. Zhang (2006), A regulatory effect
of ENSO on the time-mean thermal stratification of the equatorial
upper ocean, Geophys. Res. Lett., 33, L07710, doi:10.1029/