Meltwater from glaciers and ice sheets will impact the system of ocean currents that move heat around the world, and drive the climate. Scientists are now observing fluctuations in these currents.
About a quarter of our planet’s heat flux (the heat that is moved around the world) is driven by a current called the Atlantic Meridional Overturning Circulation (AMOC).
The current is powered by variations in water density: Water that is cold or salty sinks; water that is warm and less saline rises. Today, cold water sinks in the North Atlantic and flows southwards, while warm waters at the surface flow northwards in a current called the Gulf Stream, which keeps the climate in northern Europe unusually mild for its latitude.
If water in the northern hemisphere gets too warm, or too fresh, then it will not be dense enough to sink, and will create a “traffic jam”, preventing the current from flowing as it should.