What is the salt content of seawater?

As we all know, the water in the sea is not drinkable because it is salt water with a very high salt content. However, the salinity of the water in each ocean may be different because the salinity of seawater is affected by many factors, such as the evaporation of seawater. In addition, the melting of glaciers will also have a very large impact on the salinity of seawater. The following introduces relevant knowledge about the salinity of seawater.

What is the salt content of seawater?

Seawater is salty because it contains various salts. On average, there are 35 grams of salt in every 1,000 grams of seawater. It has been estimated that if all the salt in the seawater were extracted and spread on land, a salt layer 153 meters thick would be obtained; if spread on the territory of the country, the average height of the country would be about 2,400 meters above sea level.

The average salinity of the Pacific Ocean is 35‰, but the salt content in different sea areas varies greatly. The distribution characteristics of the salinity of the ocean's surface seawater are as follows: near the equator (slightly north), the salinity is low because precipitation is greater than evaporation, dropping from 34.5‰ in the west to 33‰ in the east; in the north and south subtropical waters, because they are under the control of the tropical high-pressure belt all year round, evaporation is greater than precipitation, and the seawater salinity is relatively high, especially in the subtropical regions of the southern hemisphere, generally 35-35.5‰ in the northern hemisphere and 36-36.5‰ in the southern hemisphere; in high-latitude regions, due to low temperature, evaporation weakens, and salinity decreases, with the northern North Pacific below 32‰ and the southern South Pacific at 33.5‰. The Yellow Sea and the East China Sea in the western Pacific Ocean have low salinity, less than 34‰, due to the influence of continental runoff, and have obvious seasonal changes. Close to the Isthmus of Central America and the southern coast of Chile, the salinity of the seawater is low, less than 33‰, because precipitation is greater than evaporation. In short, the distribution pattern of salinity in the Pacific Ocean's surface water is that the salinity is higher in the subtropical waters and gradually decreases towards the equator and the poles. In terms of the eastern and western seas, the salinity is lower along the western Asian continental coast, and the salinity is also lower along the eastern coasts of North and South America where cold currents pass through and in rainy areas.

Salinity Definition:

After the definition of salinity was first established in 1902, with the development of marine science, the requirements for the accuracy of salinity values ​​have become increasingly higher, so the definition of salinity has been revised several times.

The first definition was in the late 19th century, when some European countries held an international ocean conference. In order to unify observation data, an expert group was established to study issues related to the salinity, chlorinity (see seawater chlorinity) and density of seawater. Under the leadership of MHC Knudzen, the team proposed a method to determine salinity, which involves taking a certain amount of seawater sample, acidifying it with hydrochloric acid, then adding chlorine water, evaporating it, and continuing to heat it, and finally drying it at 480°C to constant weight, and weighing the remaining salt. According to this measurement method, the salinity of seawater is defined as: "The number of grams of inorganic salts contained in 1 kg of seawater after all the bromine and iodine in it are replaced by equivalent amounts of chlorine and all carbonates are converted into oxides." It is represented by the symbol "S‰" and the unit is grams per kilogram.