Climate's Role in the Odd Couple Affair
Latitude affects the temperature of ocean water. Cold winds blowing across the ocean at high latitudes cool and evaporate the water. If it is cold enough, sea ice will form. The sea ice is fresher water than the sea water. Since the salts are left behind when the sea ice forms, the cold water becomes more dense and sinks deep into the ocean. This sinking of cold dense water at high latitudes is due to temperature and salinity differences. The sinking and spreading of cold water is known as --here come the big words--the Thermohaline Circulation or the Meridional Overturning Circulation.
The existence of this very cold water in the ocean basins has been known about for a long, long time. There is much more of this deep water than there is of the surface water. The currents in the deep water are not as strong as those of the surface water.
So what does the atmosphere have to do with deep ocean movement? Picture this. Clouds, which are part of the atmosphere, block the sun's rays from the ocean. The ocean cools. These same clouds could also bring rain, which is fresh water. The fresh water reduces the salinity of the ocean. Winds blow in and evaporate some of the ocean water. The water goes up and the salt stays behind. Let's see if we got that. Temperature, precipitation, and wind can affect density, which affects deep ocean movement.