Seawater, billions of years ago, having dissolved a mass of chemical compounds in itself, was transformed into a solution containing many unique microcomponents. One of the main characteristics of sea water is its salinity. The Mediterranean Sea is the most saline on the planet after the Red.
A bit of history
The Mediterranean, scientists say, was once part of Tethys, an ancient ocean that stretched from America to Asia.
Five million years ago, due to severe drought, the sea was a lot of lakes and began to flood only at the end of the drought, many years later. This was facilitated by a gigantic waterfall that cut through the barrier that served as a barrier between the sea and the Atlantic Ocean. Gradually, as the sea filled with the waters of the Atlantic Ocean, this obstacle disappeared, and the Strait of Gibraltar formed.
Characteristic
The Mediterranean Sea is located between Africa and Europe, and its shape is constantly changing. To date:
- its area is 2.5 million km 2 ;
- water volume - 3.6 million km 3 ;
- average depth - 1541 m;
- maximum depth reaches 5121 m;
- water transparency 50-60 m;
- the salinity of the Mediterranean Sea in percentage places reaches 3.95%;
- total annual river flow 430 km 3 .
This is one of the warmest and salty water areas of the oceans.
The Mediterranean Sea got its name because of its location among the lands that made up the whole world known to the ancients. The sea in the middle of the Earth - as the ancient Greeks called it, the Romans called the Inland Sea, or Ours . Large green water - so the ancient Egyptians dubbed the pond.
Water composition
Sea water is not just H 2 O, but a solution of a myriad of substances, where many chemical elements are combined in various formulas. Of these, chlorides account for the largest number (88.7%), among which NaCl is the leading one - ordinary table salt. Sulfuric acid salts - 10.8%, and only 0.5% of the rest of the water is formed by other substances. These proportions determine the salinity of the Mediterranean Sea. In ppm, this figure is 38 ‰. This allows you to get table salt from sea water, evaporating it.
During the many years of development of life on Earth, sea water has become a salt supplier, transforming into salt formations. Some of the largest salt mines in Europe are located in Sicily - the largest island of the Mediterranean Sea.
Salt deposits can form at different depths, which sometimes reaches 1 km, and in some cases these are salt lakes at the level of the Earth's surface - Uyuni solonchak, a salt-dried lake.
Oceanographers found that in the oceans contains 48 quadrillion tons of salt, and even with its constant extraction, the composition of sea water will not change.
Salinity concept
Determining the salinity of the Mediterranean Sea, as well as other water bodies, take into account the mass of salts in grams contained in one kilogram of sea water.
It is calculated in ppm and is due to the fact that a large volume of river water or thawed continental glaciers enters the seas. The low salinity of the equatorial zone is due to tropical rains that desalinate water.
Salinity changes with increasing depth. Further 1500 meters it is practically nonexistent.
For sampling, for its measurement using special samplers, which allow you to take samples from different depths and from different water layers.
Where so much salt in seawater comes from
For some time, scientists were of the opinion that rivers brought salt, but this hypothesis was not confirmed. The only assumption now held: the ocean became salty in the process of its birth and transformation, since ancient animals could not live in fresh or slightly salted water. At the bottom of the Mediterranean Sea, in the Greek city of Zakynthos, organized structures were found that are more than three million years old, but what percentage of the salinity of the Mediterranean Sea was in those days is unknown.
Academician V.I. Vernadsky believed that marine inhabitants — animals and plants — extracted silicon salts and carbon dioxide from the deep sea, which the rivers brought to form their shells, skeletons, and shells. And as they die off, these same compounds settled on the seabed in the form of organic deposits. Thus, marine living creatures have kept the salt composition of sea water unchanged for centuries.
What causes salinity
All seas are part of the ocean. But there are seas that break deep into the land and connect with the ocean only through a narrow strait. These seas include:
- Mediterranean
- Black;
- Azov;
- Baltic
- Red.
All of them can be either very salty, because they are affected by hot air, or almost fresh due to the rivers flowing into them, which they dilute with their water.
The salinity of the Black and Mediterranean Seas is largely influenced by the hot climate.
Despite the fact that the Black Sea is located in the Mediterranean basin and is connected with shallow straits of the Dardanelles and the Bosphorus, it has lower salinity. The indicator is lower not only as a result of difficult water exchange with the Atlantic Ocean, but also due to a significant amount of precipitation and the influx of mainland waters. In the open part of the sea, this indicator varies from 17.5 ‰ to 18 ‰, and in the coastal strip of the Northwest region it is below 9 ‰.
The salinity of the seas differs from the salinity of ocean waters, which is due to the free exchange of water between the seas and the ocean, runoff and climate influence. On the surface of the Mediterranean Sea, water salinity increases over the stretch from the Strait of Gibraltar to the shores of Egypt and Syria, and reaches 36 near Gibraltar.
Climate
Due to the location of the Mediterranean Sea in the subtropic belt, the Mediterranean climate prevails here: hot summers and mild winters. January air temperature on the northern coasts of the sea is in the region of +8 .. + 10 ° , and on the south - is +14 ... + 16 ° . The hottest month is August, when the maximum temperature near the east coast reaches +28 ... + 30 ° . Winds walk over the sea year-round, and in winter cyclones from the Atlantic invade, causing storms.
From the African deserts a sirocco erupts, a sultry wind that carries a lot of dust and the temperature often reaches + 40 ° C and above. All these factors affect the salinity of the Mediterranean Sea, increasing its percentage due to evaporation of water.
Fauna
The fauna of the Mediterranean Sea is characterized by a large species diversity. This is due to a favorable environment and a long history. More than 550 species of fish live here, 70 of which live in a limited range.
Huge shoals are concentrated here during the winter season, and in the rest of the year individuals stay absent-minded, especially during spawning or fattening. For this, numerous species of fish migrate to the Black Sea.
The south-eastern region of the Mediterranean Sea, which is affected by the flow of the Nile River, is one of the most fruitful. The Nile waters generously supplied sea water with a large amount of nutrients and mineral suspensions, which affected the salinity of the Mediterranean Sea.
But in the early sixties, the Aswan hydroelectric station was built, as a result of which river flow and water redistribution during the year sharply decreased. This significantly worsened the living conditions of marine individuals, and their number decreased. As the area of desalination decreased, useful salts began to flow into the sea to a lesser extent. This led to a significant reduction in the amount of zooplankton and phytoplankton, respectively, the number of fish (sardines, mackerel, horse mackerel, etc.) decreased and fisheries decreased.
Unfortunately, the pollution of the Mediterranean Sea increases in direct proportion to the development of technological progress, and the ecological situation raises the fears of scientists. Let's hope that all concerned people will unite and preserve the wealth of the marine world for posterity.