The Gulf Stream or "AMOC" (Atlantic Metidonial Overturning Circulation) is the movement of warm water from the Gulf of Mexico north-eastwards across the Atlantic Ocean to the seas around western Europe. It is the warming effect of the Gulf Stream that enables north-west Europe to enjoy a temperate climate, despite a northerly latitude.
High salinity water warmed by high solar temperatures in the tropics moves North parallel to the coast of the United States before swinging eastwards across the Atlantic towards Northern Europe. This warm water increases temperatures of Northern European countries by 4 - 6deg C compared to countries at similar latitudes elsewhere. As the dense salt water reaches the Arctic it sinks below the fresh water melt from the Polar Ice Pack and Greenland. This water movement causes significant nutrient movement in the North Atlantic which has produced huge diversity in marine life.
There is increasing evidence from NOAA, the Met Office and various other scientific bodies that show the Gulf Stream is slowing (15 - 20% reduction in 50 years). This has been linked to increasing meltwater from the artic ice pack and Greenland, caused by human induced climate change, causing the AMOC to deflect further South. This may have devastating consequences for Northern European weather and world climate generally. As ocean currents are linked the knock effects of the AMOC slowing or reducing will have an impact on other currents world wide.