What does salinity depend on? What determines the salinity of sea water? Why are the oceans salty
Sea water has an unpleasant bitter-salty taste, which is why it is impossible to drink it. However, it is not the same in all seas. Many are interested in what the salinity of water depends on, 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 water bodies. 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, and regardless of the region. Researchers do not give explanations for such a geographical division. Perhaps the answer lies at the very beginning of the development of life on our planet?
It is known that the salinity of water is influenced by:
- sodium chlorides;
- magnesium chlorides;
- other salts.
Probably, certain areas of the earth's crust are rich in deposits of such substances, in contrast to neighboring regions. Although such an explanation is rather fragile: if you take into account the factor of sea currents, the salinity level should have leveled off sooner or later.
Causes of high salinity
Scientists put forward several theories that explain this phenomenon. Some argue that the increased amount of salt is the result of the evaporation of the water of the flowing rivers. Others are supporters of the theory that explains the high salinity by washing out stones and rocks. And some associate this composition of water with active volcanoes.
To many, the hypothesis that claims that an increased amount of salt in the sea appears with the water of the rivers flowing into it may seem strange. Nevertheless, any river moisture contains salt. Of course, it is much less than, say, in any ocean.
Therefore, when a river enters the sea, its composition is desalinated. But after the evaporation of river water, salt remains in the reservoir. Of course, the amount of river impurities is small, but given that the process lasts millions of years, a lot of them have accumulated in sea water. They settle at the bottom, forming huge rocks and boulders 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 the culprit of the bitter taste of sea water.
Explanations that indicate what the salinity of sea water depends on 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 acids 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 its usual salinity.
There are other assumptions, which include:
- Salt-bearing winds.
- Soils that, passing water through themselves, enrich it with salts and throw it into the ocean.
- Salt-forming minerals that, while 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 of the seas is the most salty?
Scientists have come to a consensus that this is the Red Sea. The composition of one liter of its water includes 41 g of salts. Compared to other reservoirs, 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 even less - only 5 g. But in the water of the oceans it is 34 grams.
Why is the sea salty: Video
The main feature that distinguishes water oceans from the waters of the land, is their high salinity. The number of grams of substances dissolved in 1 liter of water is called salinity.
Sea water is a solution of 44 chemical elements, but salts play a primary role in it. Table salt gives water a salty taste, while magnesium salt gives it a bitter taste. Salinity is expressed in ppm (%o). This is a thousandth of a number. In a liter of ocean water, an average of 35 grams of various substances are dissolved, which means that the salinity will be 35% o.
The amount of salts dissolved in will be approximately 49.2 10 tons. In order to visualize how large this mass is, we can make the following comparison. If all sea salt dry spread over the surface of the entire land, then it will be covered with a layer 150 m thick.
The salinity of the ocean waters is not the same everywhere. Salinity is influenced by the following processes:
- evaporation of water. In this process, salts with water do not evaporate;
- ice formation;
- fallout, lowering salinity;
- . The salinity of the ocean waters near the continents is much less than in the center of the ocean, since the waters desalinate it;
- melting ice.
Processes such as evaporation and ice formation contribute to an increase in salinity, while precipitation, river runoff, and melting ice lower it. Evaporation and precipitation play the main role in changing salinity. Therefore, the salinity of the surface layers of the ocean, as well as temperature, depends on latitude-related.
The main feature of the water of the oceans and seas is its salinity. In science, it is customary to measure salinity by the number of grams of salts contained in a kilogram of sea water. Since a kilogram is equal to a thousand grams, then, by measuring the salinity in grams per kilogram, we, in essence, express it in thousandths - ppm. Therefore, they say that salinity is "expressed in ppm". Salinity was denoted by the capital Latin letter S, and ppm - ° / 00.
The salinity of the surface water of the Black Sea is eighteen ppm. This means that one kilogram of Black Sea water contains eighteen grams of various salts.
The average salinity of the waters of the World Ocean is thirty-five ppm (S=35°/00). In the surface water of the oceans and seas, rather significant deviations from this average value are observed. This depends on the fact that the amount of water evaporating from any part of the surface of the ocean, and the amount of precipitation falling in the same time on the same surface, is not the same at different latitudes. In the equatorial zone, a layer of precipitation about 2 m high falls during the year, but less water evaporates; therefore, an excess of fresh water is obtained, which lowers the salinity of the surface water to about 34 ° / 00.
In the subtropical zone at latitudes between 30-35 °, clear, dry weather prevails, there is little precipitation, and evaporation is very large. The predominance of evaporation over precipitation leads to the fact that the salinity of the surface water of the World Ocean in the subtropics is above average: in the Northern Hemisphere 38 ° / 00, and in the Southern - 37 ° / 00.
In temperate latitudes, the amount of precipitation is greater than in the subtropics, and evaporation is less; therefore, with distance from the tropics to the north in the Northern Hemisphere and to the south in the Southern Hemisphere, the salinity gradually approaches normal. In the subpolar zones, where evaporation is sharply reduced, the salinity of surface water is less than the average salinity of the World Ocean. It does not exceed here 33-34 ° / 00
Thus, on the surface of the World Ocean, there is a lower salinity in the equatorial zone and an increased one - to the north and south of it - in the subtropical zones. Toward the poles, salinity gradually decreases, becoming normal in temperate latitudes (S=35 °/00). This pattern is somewhat violated by ocean currents. Cold currents carry water of low salinity from the subpolar zones to temperate latitudes, and currents coming from the subtropics carry more saline water to temperate latitudes.
In the coastal parts of the World Ocean, especially near the mouths of large rivers, such as, for example, the Amazon, Congo, Yenisei, Lena, and Ob, the salinity of the water on the surface drops sharply.
All the differences in the salinity of ocean water, which we talked about, are observed only on the surface of the oceans. They can be seen in a layer of water several hundred meters thick. The salinity of the deep waters of the World Ocean is almost the same everywhere and is equal to 35 ° / 00.
How did the salts in sea water get into it? On their way, rivers dissolve the salts that make up the rocks, and then carry the salts into the oceans and seas.
Careful chemical analyzes showed that sea water contains all the chemical elements common on land. It is interesting that the ratios between them in different parts of the World Ocean are the same, i.e. chemical composition salt of the oceans is constant.
It turned out that the salts dissolved in sea water are in it in the following proportion (in%):
Chlorides (salts of hydrochloric acid). . . 88.7
Sulfates (salts of sulfuric acid). . . 10.8
Carbonates (salts of carbonic acid). . . 0.3
Other salts………. 0.2
In all oceans, these ratios are preserved. This once again shows the unity of the World Ocean and indicates that the water of the oceans mixes well.
IN river water, unlike the sea, most of all not chlorides, but carbonates. What happens to them in the ocean? They are used by living creatures living in sea water to build their shells and skeletons.
SEA WATER TEMPERATURE
It is known from physics that water has a very high heat capacity compared to air. It takes one calorie of heat to heat one cubic centimeter, or one gram, of water by 1°. The same calorie can heat more than three thousand cubic centimeters of air by 1 °.
Therefore, the temperature of the surface of the water in the World Ocean strongly affects the temperature of the air above it, and, consequently, the climate of those areas where this air penetrates due to the prevailing winds.
The most heat water on the surface of the World Ocean away from the coast is observed in the equatorial zone. The average annual temperature there reaches 28 °. Near the coast in shallow water, the water warms up even more. Interestingly, during the year in the equatorial zone, the temperature of ocean water almost does not change. The highest temperature is usually no more than one degree above the average. The minimum temperature is just as low as the average. This happens because in the equatorial zone the arrival of solar heat during the year is very uniform, since the length of the day all year round is approximately 12 hours, and the sun at noon is near the zenith.
From the equatorial zone and to the north and south, the average annual temperatures of the surface of the water begin to decrease and in the subtropics reach 20 °. In the subtropical zone, the sun rises almost to the zenith at noon in summer. At this time, the day is much longer than the night. In winter, the days are shorter and the sun does not rise as high at noon. Therefore, the difference in the arrival of solar heat in summer and winter is significant. The highest and lowest water temperatures can differ from the annual average by up to 5°. For example, the average annual water temperature is 22°, the highest (maximum) is 27°, and the lowest (minimum) is 17°. Accordingly, the air temperature also changes.
From the subtropics towards the polar circles, the average annual temperature of surface water drops rapidly and finally, in winter, reaches the temperature at which ice forms,
I had a chance to ride to the seas in my life. Indeed, everyone is different! Somewhere you can safely swim and even dive - and even your eyes practically do not sting. And somewhere you can’t even plunge headlong, otherwise the salt will turn your hair into straw, and your eyes will be red until the next day. But what is the reason for this difference in salinity between different seas?
What determines the salinity of sea water
For a while, I thought it 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 the water is really 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 most salty and why
The most- The Dead Sea is 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 in the sea living organisms cannot live- do not withstand the salinity of water. That is why the sea got its name.
The reasons for this accumulation of salt are commonplace. Here only one river flows- Jordan. AND no river flows from the Dead Sea. Also close to the Dead Sea very hot.
It turns out that salt simply has nowhere to go from the sea. Water evaporates, salt does not disappear - and a concentrated salt solution is obtained.
But there is another plus - because of such salinity It is almost impossible to drown in the Dead Sea. The water itself will push you to the surface.
Seventy percent of the surface of our planet is covered with water - most of it is 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 so good?" 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 the water from the surface of the ocean evaporates, the salt does not erode and remains. Her concentration is increasing. The freezing process has a similar effect. Glaciers contain the largest supply of fresh water on the planet. The salinity of the oceans during their formation increases.
The opposite effect is characterized by the melting of glaciers, in which the salt content decreases. Salt also comes from rivers flowing into the ocean and 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, the concentration of salt in the oceans is always greater than in the seas, and location does not have any effect on this. This fact is not explained.
Salinity is due to the presence of magnesium and sodium. One of the options for explaining the different concentrations is the presence of certain land areas enriched in deposits of such components. However, such an explanation is not very plausible, if we take into account the sea currents. Thanks to them, over time, the salt level should stabilize throughout the volume.
World Ocean
The salinity of the ocean depends on the geographical latitude, the proximity of rivers, the climatic features of objects etc. Its average value according to the measurement is 35 ppm.
Near the Antarctic and the Arctic in cold areas, the concentration is less, 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.
In the Atlantic and Pacific oceans, the concentration of salt is approximately the same, 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 the presence of salt in the ocean. Scientists believe that the reason is the ability of water masses to destroy the rock, leaching easily soluble elements from it. This process is ongoing. Salt saturates the seas and gives a bitter taste.
However, there are diametrically opposed opinions on this issue:
Volcanic activity decreased over time, and the atmosphere cleared of vapor. 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.
