The earth has spent most of its recent million years in ice ages with brief interludes, called "interglacial periods". The question of what mechanism causes the planet to emerge from an interglacial is relevant to understanding the current global warming process. The thermohaline circulation of the North Atlantic is known to be a very significant mechanism in regulating climate because it transports massive amounts of heat from the tropical regions to the North Atlantic and keeps Europe much more mild than might be expected for such high latitude. But Knorr and Lohmann (2003) suggest that oceanic changes around Antarctica can have a profound influence on events in the North Atlantic Ocean. From a modeling study they show that slowly increasing sea surface temperatures around Antarctica and receding sea-ice cover can switch on the thermohaline circulation and pump heat northward to accelerate the glacial melting. Stocker (2003) provides an very nice summary of this research.
Reference
Knorr, G., and G. Lohmann, 2003: Southern ocean origin for the resumption of Atlantic thermohaline circulation during deglaciation. Nature 424, 532-536.
Stocker, T. F., 2003: South dials north. Nature 424, 496-499.