Asymmetry of the Atlantic and Pacific sea surface salinity (SSS) is recognized as an important element of the global ocean thermohaline circulation. However, a threshold of such asymmetry that may trigger a true global deep-ocean conveyor has not yet been examined. A combined effect of the Atlantic-Pacific and the Southern Ocean surface salinity asymmetries also has not yet been clearly shown. We address these issues and conclude that Atlantic-Pacific SSS asymmetry is one of the most critical elements for maintaining the global ocean conveyor. Our experiments suggest, albeit preliminary, that high-latitudinal freshwater impacts, as a mechanism of altering global ocean thermohaline circulation, may be less effective than inter-basin freshwater communications.