Atlantic high salt differentiation, Pacific low salt differentiation (review)

　Water vapor evaporated in the tropical Atlantic is carried by trade winds, some of which are brought over the low mountains of Central America to the Pacific Ocean. On the other hand, water vapor generated in the tropical Pacific and Indian Oceans is returned to the Pacific Ocean by the East Asian monsoon rains. Some of the water vapor reaches the west coast of North America on the prevailing westerly winds, but is intercepted by the Rocky Mountains and turned into rain, which is eventually returned to the Pacific Ocean.

　

This results in higher salinization in the Atlantic and lower salinization in the Pacific. Compared to the subarctic region, the Atlantic Ocean has higher salinity. The North Atlantic subarctic zone has a salinity of about 34-36‰, while the North Pacific subarctic zone has a salinity of 32-34‰ (see figure above).

　 ‰ (permil) is a thousandth of a gram, so one kilogram of seawater contains the equivalent of 34.5 grams of salt in the Atlantic and 32.5 grams in the Pacific. Although the difference is only 2 grams, this difference creates the density difference that drives the ocean general circulation.

(How much is 2g of salt? (It is about 4 light pinches with the thumb and forefinger)