One of the world’s great geophysical phenomena is the flow of warm water, and associated weather, from the Gulf of Mexico across the Atlantic towards western Europe. This flow is known as the Gulf Stream and the North Atlantic Drift and although huge in scale, it is merely a surface feature of a much bigger ocean process.
As this current travels north, warm water evaporates, leaving the surface water saltier and denser. Then, as it reaches the Arctic, the water begins to cool and freeze, making the remaining liquid even saltier and denser.
This salty, dense water sinks to the bottom of the Atlantic Ocean and begins the long journey back to the tropics and beyond, at depths of several thousand meters, where it begins the long cycle again. Any given parcel of water takes a thousand years to complete this conveyor belt ride.
The whole process is known as ...
