The freshwater evaporating from the North Atlantic subtropics feeds excess rainfall in the Pacific Ocean's western tropical regions. The Atlantic gets salty, the Pacific gets fresher. However the freshwater export across Central America can't explain the salty South Atlantic. That may be explained by the removal of water vapor from the South Atlantic subtropics to the Antarctic Circumpolar Current by a mean southwest-directed wind. The South Atlantic gets saltier and the excess freshwater is carried into the Indian and ultimately to the Pacific Ocean by the Antarctic Circumpolar Current. Both routes of water vapor, from the North Atlantic and from the South Atlantic, make for a salty Atlantic. But that's not all, there is also an influx of Indian Ocean water around the southern rim of Africa by the Agulhas Current. This is referred to as the Agomes interesting.

Naturally as water vapor is removed from the Atlantic Ocean by the winds and the Atlantic gets saltier there must be some compensating action that brings freshwater back to the Atlantic, otherwise the Atlantic will continuously become saltier, the Pacific fresher. Compensation is accomplished by interocean exchange, the fresher Pacific waters make their way to the salty Atlantic. Much of the interocean exchange is part of a sluggish global scale circulation associated with North Atlantic Deep Water.

Cooling of the salty surface water of the northern North Atlantic leads to the formation of North Atlantic Ocean Deep Water. The production rate is thought to be about 15 Sv. NADW flows southward between 1000 and 3500 m where upon reaching the Antarctic Circumpolar Current it upwells and advected eastward around Antarctica, into the Indian and Pacific Oceans. Slowly the NADW water enters into the upper kilometer of the ocean, altered in temperature and salinity. This surface layer water winds it way back to the Atlantic Ocean.http://eesc.columbia.edu/courses/ees/climate/lectures/saltyatlantic.html