The warm waters of the Gulf are very salty due to surface water evaporation. The Earth’s rotation helps to push this water to the north east where it becomes  cooler, saltier, denser and heavier. It then sinks pulling the current behind it and heads back south as a deep water current.
Scientists are extremely worried that fresh water pouring into the northern ocean from melting glaciers will mix with the salt water of the current making it lighter and unable to sink. It is disturbing that from measurements taken in the last few years there is already a decline in the vigour of the circulation, and studies indicate that unlike other climate changes, ocean currents can shift or stop in just a few years.
