The consequences are not quite yet understood, but eventually it could change forecasts of one of the worst-case global warming scenarios - still considered unlikely this century - in which the mixing stops and climate chaos ensues.
Scientists describe it as a giant ocean conveyor belt that moves ocean water around the globe.
The engine of this belt, where water of different temperatures and salinity mix, was thought to be near Canada.
Scientists reported Thursday in the journal Science that it appears to be closer to Scotland.
