Our planet is covered with water by 70%, of which more than 96% is occupied by oceans. This means that most of the water on Earth is salty. What is water salinity? How is it determined and what does it depend on? Is it possible to use such water on the farm? Let's try to answer these questions.
What is water salinity?
Most of the water on the planet has salinity. It is usually called sea water and is found in oceans, seas and some lakes. The rest is fresh, its amount on Earth is less than 4%. Before you understand what the salinity of water is, you need to understand what salt is.
Salts are complex substances that consist of cations (positively charged ions) of metals and anions (negatively charged ions) of acid bases. Lomonosov defined them as “fragile bodies that can dissolve in water.” There are many substances dissolved in sea water. It contains sulfates, nitrates, phosphates, cations of sodium, magnesium, rubidium, potassium, etc. Together these substances are defined as salts.
So what is water salinity? This is the content of substances dissolved in it. It is measured in parts per thousand - ppm, which are designated by a special symbol - %o. Permille determines the number of grams in one kilogram of water.
What determines the salinity of water?
In different parts of the hydrosphere and even at different times of the year, the salinity of water is not the same. It changes under the influence of several factors:
- evaporation;
- ice formation;
- precipitation;
- melting ice;
- river flow;
- currents.
When water evaporates from the surface of the oceans, salts remain and do not erode. As a result, their concentration increases. The freezing process has a similar effect. Glaciers contain the largest reserve of fresh water on the planet. During their formation, the salinity of the waters of the World Ocean increases.
The melting of glaciers has the opposite effect, reducing the salt content. In addition to them, the source of fresh water is precipitation and rivers flowing into the ocean. The level of salts also depends on the depth and nature of the currents.
Their greatest concentration is on the surface. The closer to the bottom, the less salinity. influence the salt content in a positive direction; cold ones, on the contrary, reduce it.
Salinity of the World Ocean
What is the salinity of sea water? We already know that it is far from the same in different parts of the planet. Its indicators depend on geographic latitudes, climatic features of the area, proximity to river objects, etc.
The average salinity of the waters of the World Ocean is 35 ppm. Cold areas near the Arctic and Antarctic are characterized by lower concentrations of substances. Although in winter, when ice forms, the amount of salts increases.
For the same reason, the least saline ocean is the Arctic Ocean (32%). The Indian Ocean has the highest content. It covers the Red Sea and Persian Gulf region, as well as the southern tropical zone, where salinity is up to 36 ppm.
The Pacific and Atlantic oceans have approximately equal concentrations of substances. Their salinity decreases in the equatorial zone and increases in subtropical and tropical regions. Some are warm and balance each other out. For example, the non-salty Gulf Stream and the salty Labrador Current in the Atlantic Ocean.
Salinity of lakes and seas
Most lakes on the planet are fresh, as they are fed mainly by sediments. This does not mean that there are no salts in them at all, just that their content is extremely low. If the amount of dissolved substances exceeds one ppm, then the lake is considered saline or mineral. The Caspian Sea has a record value (13%). The largest freshwater lake is Baikal.
The concentration of salts depends on how the water leaves the lake. Fresh water bodies are flowing, while saltier ones are closed and subject to evaporation. The determining factor is also the rocks on which the lakes were formed. Thus, in the region of the Canadian Shield, rocks are poorly soluble in water, which is why the water bodies there are “clean”.
The seas are connected to the oceans through straits. Their salinity is slightly different and affects the average values of ocean waters. Thus, the concentration of substances in the Mediterranean Sea is 39% and is reflected in the Atlantic. The Red Sea, with an indicator of 41%o, greatly raises the average. The saltiest is the Dead Sea, in which the concentration of substances ranges from 300 to 350%o.
Properties and significance of sea water
Not suitable for economic activity. It is not suitable for drinking or watering plants. However, many organisms have long adapted to life in it. Moreover, they are very sensitive to changes in its salinity level. Based on this, organisms are divided into freshwater and marine.
Thus, many animals and plants that live in the oceans cannot live in the fresh water of rivers and lakes. Edible mussels, crabs, jellyfish, dolphins, whales, sharks and other animals are exclusively marine.
People use fresh water for drinking. Salted water is used for medicinal purposes. Water with sea salt is consumed in small quantities to restore the body. The healing effect comes from swimming and bathing in sea water.
Sea water has an unpleasant bitter-salty taste, which is why it is impossible to drink. However, it is not the same in all seas. Many people are interested in what determines the salinity of water, and experts find many explanations for this.
The water in all the seas on the planet has a different composition. Salinity, which is measured in ppm, depends on the geographical location of the reservoirs. According to experts, the further north the sea is, the higher this figure. Consequently, the seas and oceans of the southern part of the planet are less salty.
However, there are exceptions to any rule - the water in the oceans is much saltier than in the seas, regardless of the region. Researchers do not provide an explanation for this geographical division. Maybe the answer lies at the very beginning of the development of life on our planet?
It is known that water salinity is influenced by:
- sodium chlorides;
- magnesium chlorides;
- other salts.
It is likely that certain areas of the earth's crust are rich in deposits of such substances, in contrast to neighboring regions. Although this explanation is quite fragile: if we take into account the factor of sea currents, the salinity level should have leveled off sooner or later.
Causes of increased salinity
Scientists put forward several theories that explain this phenomenon. Some argue that the increased amount of salt is the result of evaporation of water from inflowing rivers. Others are proponents of a theory that explains the high salinity by the washing away of stones and rocks. And some associate this composition of water with active volcanoes.
Many may find the hypothesis strange, which states that an increased amount of salt in the sea appears with the water of the rivers flowing into it. Nevertheless, any river moisture contains salt. Of course, there is much less of it than, say, in any ocean.
Therefore, when a river enters the sea, its composition is desalinated. But after the river water evaporates, the salt remains in the reservoir. Of course, the amount of river impurities is small, but if you consider that the process lasts millions of years, a lot of them have accumulated in sea water. They settle to the bottom, forming huge rocks and blocks there for thousands of years. But the sea current is very strong - it can destroy any stones. This process is quite long and constant. By the way, it is he who is responsible for the bitter taste of sea water.
Explanations indicating what determines the salinity of sea water include the presence of underwater volcanoes. Periodically, they emit a large amount of various substances, including salts.
Volcanoes were very active during the formation of the Earth. They released acid into the atmosphere. It is assumed that due to frequent acid rain, the water in the seas and oceans was initially acidic. However, when interacting with magnesium, calcium or potassium, salts were obtained. It was in this way that the water acquired the usual salinity.
There are other assumptions, which include:
- Salt-carrying winds.
- Soils that, passing water through themselves, enrich it with salts and throw it into the ocean.
- Salt-forming minerals that, located under the ocean floor, penetrate through hydrothermal vents.
Which sea is the saltiest
Sea water is perhaps the most abundant substance on Earth. Many people associate a full and healthy vacation with warm waves and sunny beaches. As mentioned above, all reservoirs have their own mineral composition. But which sea is the saltiest?
Scientists have come to a consensus that this is the Red Sea. One liter of its water contains 41 g of salts. Compared to other bodies of water, this is a very high figure. For example, in the Mediterranean Sea it is 39 g, much less salt in the Black Sea - 18 g, and in the Baltic Sea it is even less - only 5 g. But in ocean water it is 34 grams.
Why is the sea salty: Video
I have had the opportunity to travel to the seas in my life. And it’s true, everyone is different! Somewhere you can calmly swim and even dive - and even your eyes practically don’t sting. And somewhere you can’t even plunge your head into it, otherwise your hair will turn into straw from the salt, and your eyes will be red until the next day. But what is the reason for this? differences in salinity of water in different seas?
What determines the salinity of sea water?
For a while it seemed to me that this was just self-deception. Indeed, why should there be any differences between the seas!
But long hours on the Internet and reading books told me: the salinity of water really is different for each sea. AND it depends on the following things:
The ratio of all these parameters determines how salty the sea will be.
Which sea is the saltiest and why?
The most The Dead Sea is considered the saltiest– where for every liter of water there are about 200 grams of salt.
Such a high concentration of salts leads to its consequences. Simply at sea living organisms cannot inhabit– cannot withstand salinity of waters. That is why the sea got its name.
The reasons for this accumulation of salt are trivial. Here only one river flows in- Jordan. AND no river flows from the Dead Sea. Also close to the Dead Sea very hot.
It turns out that there is simply nowhere for salt to escape from the sea. The water evaporates, but the salt does not disappear - and a concentrated salt solution is obtained.
But there is another plus - because of such salinity It's almost impossible to drown in the Dead Sea. The water itself will push you to the surface.
Seventy percent of our planet's surface is covered with water - most of it in the oceans. The waters of the World Ocean are heterogeneous in composition and have a bitter-salty taste. Not every parent can answer the child’s question: “Why does sea water taste like that?” What determines the amount of salt? There are different points of view on this matter.
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What determines the salinity of water?
At different times of the year in different parts of the hydrosphere, salinity is not the same. Several factors influence its change:
- ice formation;
- evaporation;
- precipitation;
- currents;
- river flow;
- melting ice.
While water evaporates from the surface of the ocean, the salt does not erode and remains. Its concentration increases. The freezing process has a similar effect. Glaciers contain the largest supply of fresh water on the planet. The salinity of the World Ocean increases during their formation.
The opposite effect is characterized by the melting of glaciers, during which the salt content decreases. The source of salt is also rivers flowing into the ocean and atmospheric precipitation. The closer to the bottom, the less salinity. Cold currents reduce salinity, warm currents increase it.
Location
According to experts, The concentration of salt in the seas depends on their location. Closer to the northern regions the concentration increases, to the south it decreases. However, in the oceans the salt concentration is always greater than in the seas, and location has no effect on this. There is no explanation for this fact.
Salinity is determined by the presence in it magnesium and sodium. One of the options for explaining the different concentrations is the presence of certain land areas enriched with deposits of such components. However, such an explanation is not very plausible if we take into account sea currents. Thanks to them, over time, the salt level should stabilize throughout the entire volume.
World Ocean
Ocean salinity depends on geographic latitude, proximity of rivers, and climatic features of objects etc. Its average value according to measurement is 35 ppm.
Near the Antarctic and Arctic in cold areas the concentration is lower, but in winter, during the formation of ice, the amount of salt increases. Therefore, the water in the Arctic Ocean is the least salty, and in the Indian Ocean the concentration of salt is the highest.
The Atlantic and Pacific oceans have approximately the same salt concentration, which decreases in the equatorial zone and, conversely, increases in tropical and subtropical regions. Some cold and warm currents balance each other. For example, the salty Labrador Current and the unsalted Gulf Stream.
Interesting to know: How many exist on Earth?
Why are the oceans salty?
There are different points of view that reveal the essence of salt in the ocean. Scientists believe that the reason is the ability of water masses to destroy rock, leaching easily soluble elements from it. This process is ongoing. Salt saturates the seas and gives them a bitter taste.
However, there is also a diametrically opposite opinion on this issue:
Volcanic activity decreased over time and the atmosphere cleared of vapors. Acid rain fell less and less, and about 500 years ago the composition of the ocean water surface stabilized and became what we know it today. Carbonates, which enter the ocean with river water, are an excellent building material for marine organisms.
) or PSU (Practical Salinity Units) units of the Practical Salinity Scale.
| Element | Content, mg/l |
|---|---|
| Chlorine | 19 500 |
| Sodium | 10 833 |
| Magnesium | 1 311 |
| Sulfur | 910 |
| Calcium | 412 |
| Potassium | 390 |
| Bromine | 65 |
| Carbon | 20 |
| Strontium | 13 |
| Bor | 4,5 |
| Fluorine | 1,0 |
| Silicon | 0,5 |
| Rubidium | 0,2 |
| Nitrogen | 0,1 |
Salinity in ppm is the amount of solids in grams dissolved in 1 kg of seawater, provided that all halogens are replaced by an equivalent amount of chlorine, all carbonates are converted to oxides, and organic matter is burned.
In 1978, the practical salinity scale (PSS-78) was introduced and approved by all international oceanographic organizations, in which the measurement of salinity is based on electrical conductivity (conductometry), and not on water evaporation. Oceanographic CTD sounders became widely used in marine research in the 1970s, and since then salinity has been measured primarily electrically. To check the operation of electrical conductivity cells that are immersed in water, laboratory salt meters are used. In turn, standard seawater is used to check salinity meters. Standard seawater, recommended by the international organization IAPSO for calibrating salinity meters, is produced in the UK by the Ocean Scientific International Limited (OSIL) laboratory from natural seawater. If all measurement standards are met, a salinity measurement accuracy of up to 0.001 PSU can be achieved.
The PSS-78 scale produces numerical results similar to mass fraction measurements, and differences are noticeable either when measurements with precision better than 0.01 PSU are required or when the salt composition does not correspond to the standard composition of ocean water.
- Atlantic Ocean - 35.4 ‰ The highest salinity of surface waters in the open ocean is observed in the subtropical zone (up to 37.25 ‰), and the maximum is in the Mediterranean Sea: 39 ‰. In the equatorial zone, where the maximum amount of precipitation is recorded, salinity decreases to 34 ‰. A sharp desalination of water occurs in the estuary areas (for example, at the mouth of La Plata - 18-19 ‰).
- Indian Ocean - 34.8 ‰. The maximum salinity of surface waters is observed in the Persian Gulf and the Red Sea, where it reaches 40-41 ‰. High salinity (more than 36 ‰) is also observed in the southern tropical zone, especially in the eastern regions, and in the northern hemisphere also in the Arabian Sea. In the neighboring Bay of Bengal, due to the desalinating influence of the Ganges runoff with the Brahmaputra and Irrawaddy, the salinity is reduced to 30-34 ‰. The seasonal difference in salinity is significant only in the Antarctic and equatorial zones. In winter, desalinated waters from the northeastern part of the ocean are transported by the monsoon current, forming a tongue of low salinity along 5° N. w. In summer this language disappears.
- Pacific Ocean - 34.5 ‰. Tropical zones have the highest salinity (up to a maximum of 35.5-35.6 ‰), where intense evaporation is combined with a relatively small amount of precipitation. To the east, under the influence of cold currents, salinity decreases. High precipitation also reduces salinity, especially at the equator and in the westerly circulation zones of temperate and subpolar latitudes.
- Arctic Ocean - 32 ‰. In the Arctic Ocean there are several layers of water masses. The surface layer has a low temperature (below 0 °C) and low salinity. The latter is explained by the desalination effect of river runoff, melt water and very weak evaporation. Below there is a subsurface layer, colder (up to −1.8 °C) and more saline (up to 34.3 ‰), formed when surface waters mix with the underlying intermediate water layer. The intermediate water layer is Atlantic water coming from the Greenland Sea with a positive temperature and high salinity (more than 37 ‰), spreading to a depth of 750-800 m. Deeper lies the deep water layer, which is formed in winter also in the Greenland Sea, slowly creeping in a single stream from the strait between Greenland and Spitsbergen. The temperature of deep waters is about −0.9 °C, salinity is close to 35 ‰. .
The salinity of ocean waters varies depending on latitude, from the open part of the ocean to the shores. In the surface waters of the oceans, it is lower in the equator region, in polar latitudes.
| Name | Salinity, ‰ |
|---|---|
