The case of 'salt in the oceans' is poor choice of something we don't need to worry about. The macro mechanics of the oceans depend intimately on salinity. http://oceanservice.noaa.gov/facts/conveyor.html

Messing that up would be catastrophic. It is also the sort of dynamical system susceptible to bifurcation. The conveyor could potentially invert due to a threshold change in temperature or salinity. http://en.wikipedia.org/wiki/Bifurcation_theory