Is there a simple bi-polar ocean seesaw?

Using an atmosphere–ocean coupled model, the climate response to an idealized freshwater input into the Southern Ocean is studied. In response to the freshwater input, the surface waters around Antarctica freshen and cool. As the addition of freshwater continues, the fresh, surface anomalies spread throughout the world ocean in contrast to ocean-only experiments and North Atlantic experiments using coupled models. Because of the fundamental difference in altering sea surface salinity (SSS) from the two sources (northern hemisphere and southern hemisphere), a bi-polar seesaw fails to develop in the ocean, at least in our coupled atmosphere–ocean experiments. Control ocean-only experiments with mixed boundary conditions and similar short-term southern freshwater impacts match the results of the coupled experiments. Based on these experiments, we argue that the concept of ocean bi-polar seesaw should be taken with some caveats.