The currents in the Gulf Stream → are mainly pushed along the surface of the ocean by the wind. The Gulf Stream originates in the gulf of Mexico. In the Atlantic, at around 40° North – the latitude of Portugal - it splits in two. One current turns south and flows back off West Africa, staying on the surface. The other continues northwards with the north-flowing current in the Atlantic Conveyor. Here it eventually cools and sinks down to form cold deep water. Only about one-fifth of the Gulf Stream flow contributes to the overturning circulation.