Such deep stratification is efficiently produced, even in single - basin, single - hemisphere simulations, in the presence of a partially topographically blocked channel at high latitudes, provided there is also a surface meridional temperature gradient across the channel. (gfdl.noaa.gov)
In the Southern Ocean the increased meridional temperature gradient increases the strength of westerlies in all seasons at all longitudes. (realclimate.org)
WHOI published on the centennial scale Pacific Oscillation which is also blissfully ignore and Toggwieler and Briereley have published on the impact of shifting westerlies and zonal / meridional temperature gradients also blissfully ignored. (judithcurry.com)