Meridional overturning circulation refers to the global circulation pattern that transports heat from the tropics to the poles. This oceanic current system is also known as the Atlantic or thermohaline circulation. Synonyms for this term include the North Atlantic Drift, the Gulf Stream, and the Subpolar Gyre. Meridional overturning circulation directs heat from the equator towards the poles, creating a warming effect on northern and western Europe. Without this circulation, temperatures would be much cooler in these regions. Climate change has been altering the meridional overturning circulation, potentially leading to significant changes in weather patterns and sea levels.