Simulating the Equatorial Pacific Cold Tongue
Zheng, Y., Lin, J.-L. and Shinoda, T. 2012. The equatorial Pacific cold tongue simulated by IPCC AR4 coupled GCMs: Upper ocean heat budget and feedback analysis. Journal of Geophysical Research 117: 10.1029/2011JC007746.
In describing what the three researchers learned, they are quoted directly below; but italics have been added to the many words they use that are indicative of various failures of the models to do specific things correctly.
"Errors in both net surface heat flux and total upper ocean heat advection significantly contribute to the excessive cold tongue in the equatorial Pacific." "The stronger heat advection in the models is caused by overly strong horizontal heat advection associated with too strong zonal currents, and overly strong vertical heat advection due to excessive upwelling and the vertical gradient of temperature." "The Bjerknes feedback in the coupled models is shown to be weaker than in observations, which may be related to the insufficient response of surface zonal winds to SST in the models and an erroneous subsurface temperature structure," such that "the cold tongue becomes colder than the cold tongue in the observations."
In final parting words the authors say that "more work is needed on the role of the ocean model and ocean-atmosphere feedback in the growth of the double-ITCZ pattern." And, it might be added, this is but one of many aspects of the challenge of attempting to correctly chart the development of global climate change over the coming decades and centuries.
Wyrtki, K. 1981. An estimate of equatorial upwelling in the Pacific. Journal of Physical Oceanography 11: 1205-1214.