It has long been known that oceanic waters cover most of the surface of our planet. They constitute a continuous water envelope, which accounts for more than 70% of the entire geographical plane. But few people thought that the properties of ocean waters are unique. They have a huge impact on climatic conditions and economic activities of people.
Property 1. Temperature
Ocean waters can accumulate heat. Surface water (about 10 cm deep) retains a huge amount of heat. Cooling, the ocean heats the lower atmosphere, so that the average temperature of the earth's air is +15 ° C. If there were no oceans on our planet, then the average temperature would hardly reach -21 ° C. It turns out that thanks to the ability of the World Ocean to accumulate heat, we got a comfortable and cozy planet.
The temperature properties of oceanic waters change abruptly. The heated surface layer is gradually mixed with deeper waters, resulting in a sharp temperature drop at a depth of several meters, and then a gradual decrease to the bottom. The deep waters of the oceans have approximately the same temperature, measurements below three thousand meters usually show from +2 to 0 ° C.
As for surface waters, their temperature depends on geographic latitude. The spherical shape of the planet determines the angle of incidence of sunlight on the surface. Closer to the equator, the sun gives off more heat than the poles. So, for example, the properties of the oceanic waters of the Pacific Ocean directly depend on average temperature indicators. The surface layer has the highest average temperature, which is more than +19 ° C. This cannot but affect the surrounding climate, and the underwater flora and fauna. Then follows the Indian Ocean, the surface waters of which are heated to an average of 17.3 ° C. Then the Atlantic, where this figure is 16.6 ° C. And the lowest average temperatures - in the Arctic Ocean - are about +1 ° C.
Property 2. Salinity
What other properties of ocean water are modern scientists studying? Without a doubt, they are interested in the composition of sea water. Water in the ocean is a cocktail of dozens of chemical elements, and salts play an important role in it. Ocean salinity is measured in ppm. Designate it with a ‰. Promille means the thousandth of a number. It is estimated that a liter of ocean water has an average salinity of 35 ‰.
In the study of the oceans, scientists have repeatedly wondered what are the properties of ocean waters. Are they the same everywhere in the ocean? It turns out that salinity, like average temperature, is heterogeneous. The indicator is influenced by a number of factors:
- precipitation - rain and snow significantly reduce the total salinity of the ocean;
- runoff of large and small rivers - the salinity of the oceans washing the continents with a large number of full-flowing rivers is lower;
- ice formation - this process increases salinity;
- melting ice - this process lowers the salinity of the water;
- evaporation of water from the surface of the ocean - salts do not evaporate with water, and salinity rises.
It turns out that the different salinity of the oceans is explained by the geographical latitude, surface water temperature and climatic conditions. The highest average salinity at the water of the Atlantic Ocean. However, the salty point - the Red Sea, belongs to the Indian. The smallest indicator is characterized by the Arctic Ocean. These properties of the oceanic waters of the Arctic Ocean are most strongly felt near the confluence of the full-flowing rivers of Siberia. Here the salinity does not exceed 10 ‰.
Interesting fact. Total amount of salt in the oceans
Scientists did not agree on how many chemical elements are dissolved in the waters of the oceans. Estimated from 44 to 75 elements. But they calculated that just an astronomical amount of salts, about 49 quadrillion tons, was dissolved in the oceans. If you evaporate and dry all this salt, then it will cover the land surface with a layer of more than 150 m.
Property 3. Density
The concept of "density" has been studied for a long time. This is the ratio of the mass of the substance, in our case, the mass of the waters of the World Ocean, to the volume occupied. Knowledge of density is necessary, for example, to maintain the buoyancy of ships.
Both temperature and density are heterogeneous properties of ocean waters. The average value of the latter is 1.024 g / cm³. This indicator was measured at average values of temperature and salt content. However, in different parts of the World Ocean, the density varies depending on the depth of measurement, the temperature of the site and its salinity.
Consider, for example, the properties of the ocean waters of the Indian Ocean, and specifically the change in their density. The highest this indicator will be in the Suez and Persian Gulf. Here it comes to 1.03 g / cm³. In warm and salty waters of the northwestern part of the Indian Ocean, the indicator drops to 1.024 g / cm³. And in the deserted northeastern part of the ocean and in the Bay of Bengal, where there is a lot of rainfall, the lowest indicator is about 1.018 g / cm³.
The density of fresh water is lower, which is why it is somewhat more difficult to stay on water in rivers and other fresh water bodies.
Properties 4 and 5. Transparency and color
If you put in a jar of sea water, then it will seem transparent. However, with an increase in the thickness of the water layer, it acquires a bluish or greenish tint. Color change is associated with the absorption and scattering of light. In addition, suspensions of various compositions affect the color of ocean waters.
The bluish color of pure water is the result of weak absorption of the red part of the visible spectrum. At a high concentration of phytoplankton in ocean water, it acquires a blue-green or green color. This is due to the fact that phytoplankton absorbs the red part of the spectrum and reflects the green.
The transparency of ocean water indirectly depends on the amount of suspended particles in it. In the field, transparency is determined by the Secchi disk. A flat disk, the diameter of which does not exceed 40 cm, is immersed in water. The depth at which it becomes invisible is taken as an indicator of transparency in this area.
Properties 6 and 7. Sound Propagation and Conductivity
Sound waves can propagate under water for thousands of kilometers. The average propagation speed is 1500 m / s. This indicator is higher for sea water than for fresh water. The sound always deviates slightly from the line.
Salt water has a greater electrical conductivity than fresh. The difference is 4,000 times. It depends on the number of ions per unit of water volume.