How does the salinity of ocean waters change. The temperature of the waters of the oceans: what is it, what does it depend on and how is it related to a person Movement of water in the oceans Sea currents

02.05.2020

1. What determines the salinity of ocean waters?

The oceans, the main part of the hydrosphere, are a continuous water shell of the globe. The waters of the World Ocean are heterogeneous in composition and differ in salinity, temperature, transparency and other features.

The salinity of water in the ocean depends on the conditions of evaporation of water from the surface and the influx of fresh water from the land surface and with atmospheric precipitation. Evaporation of water occurs more intensively in equatorial and tropical latitudes and slows down in temperate and subpolar latitudes. If we compare the salinity of the northern and southern seas, we can establish that the water in the southern seas is more salty. The salinity of the waters in the oceans also varies depending on the geographical location, however, in the ocean, water mixing occurs more intensively than in more closed seas, therefore, the difference in the salinity of the ocean water masses will not be too sharp, as in the seas. The most saline (more than 37% o) are the ocean waters in the tropics.

2. What are the differences in ocean water temperature?

The temperature of the water in the oceans also varies depending on the geographic latitude. In tropical and equatorial latitudes, the water temperature can reach +30 °С and higher, in the polar regions it drops to -2 °С. At lower temperatures, ocean water freezes. Seasonal changes in ocean water temperature are more pronounced in the temperate climate zone. The average annual temperature of the World Ocean is 3 °C higher than the average temperature of the land. This heat is transferred to land with the help of atmospheric air masses.

3. In what areas of the ocean does ice form? How do they affect the nature of the Earth and human economic activity?

The waters of the World Ocean freeze in the arctic, subarctic and partially in temperate latitudes. The resulting ice cover has an impact on the climate of the continents, making it difficult to use cheap sea transport in the north to transport goods.

4. What is called the water mass? Name the main types of water masses. What water masses are isolated in the surface layer of the ocean?

You will find the definition of the concept of water masses in the textbook (9).

Water masses, by analogy with air masses, are named according to the geographical zone in which they formed. Each water mass (tropical, equatorial, arctic) has its own characteristic properties and differs from the rest in salinity, temperature, transparency and other features. Water masses differ not only depending on the geographical latitudes of their formation, but also depending on the depth. Surface waters are different from deep and bottom waters. Deep and bottom waters are practically not affected by sunlight and heat. Their properties are more constant throughout the world's oceans, unlike surface subs, whose properties depend on the amount of heat and light received. There is much more warm water on Earth than cold water. Residents of temperate latitudes spend their New Year holidays with great pleasure on the coasts of those seas and oceans where the water is warm and clean. Sunbathing under the hot sun, swimming in salty and warm water, people restore strength and improve health.

The ocean receives a lot of heat from the Sun - occupying a large area, it receives more heat than land. Water has high heat capacity, therefore, a huge amount of heat accumulates in the ocean. Only the upper 10-meter layer of ocean water contains more heat than the whole. But the sun's rays heat only the upper layer of water; heat is transferred down from this layer as a result of constant mixing water. But it should be noted that the water temperature decreases with depth, first abruptly, and then smoothly. At depth, the water is almost uniform in temperature, since the depth of the oceans is mainly filled with waters of the same origin, which form in the polar regions of the Earth. At a depth more than 3-4 thousand meters the temperature usually fluctuates from +2°С to 0°С.

So, the ocean absorbs heat 25-50% more than the land. The sun heats water all summer long, and in winter this heat enters the atmosphere, so without the World Ocean, such severe frosts would come on Earth that all life on the planet would die. This is its huge role for the living beings of the Earth. It has been calculated that if the oceans did not keep warm so carefully, then the average temperature on our planet would be -21 ° C, which is 36 ° lower than what we have now.

It has long been known that ocean waters cover most of the surface of our planet. They constitute a continuous water shell, 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 store heat. (about 10 cm deep) retain a huge amount of heat. Cooling, the ocean heats the lower layers of the atmosphere, due to which 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 oceans to accumulate heat, we got a comfortable and cozy planet.

The temperature properties of oceanic waters change abruptly. The heated surface layer gradually mixes with deeper waters, as a result of which a sharp temperature drop occurs at a depth of several meters, and then a gradual decrease to the very 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 the geographic latitude. The spherical shape of the planet determines the sun's rays to the surface. Closer to the equator, the sun gives off more heat than at the poles. So, for example, the properties of the ocean 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. This is followed by the surface waters of which, on average, are warmed up to 17.3 ° С. Then the Atlantic, where this figure is 16.6 ° C. And the lowest average temperatures are in the Arctic Ocean - about +1 °С.

Property 2. Salinity

What other properties of ocean waters are being studied by modern scientists? they are interested in the composition of sea water. Ocean water is a cocktail of dozens of chemical elements, and salts play an important role in it. The salinity of ocean waters is measured in ppm. Designate it with the icon "‰". Promille means a 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 the average temperature, is not uniform. The indicator is influenced by a number of factors:

the amount of precipitation - rain and snow significantly lower the overall 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 the waters, and salinity rises.

It turns out that the different salinity of the oceans is explained by the temperature of surface waters and climatic conditions. The highest average salinity is near the water of the Atlantic Ocean. However, the most salty point - the Red Sea, belongs to the Indian. The Arctic Ocean is characterized by the least indicator. 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 salinity does not exceed 10‰.

Interesting fact. The total amount of salt in the world's oceans

Scientists did not agree on how many chemical elements are dissolved in the waters of the oceans. Presumably from 44 to 75 elements. But they calculated that just an astronomical amount of salt is dissolved in the oceans, about 49 quadrillion tons. If all this salt is evaporated and dried, it will cover the surface of the land 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 matter, in our case the oceans, to the volume occupied. Knowledge of the density value 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 oceanic waters of the Indian Ocean, and specifically the change in their density. This figure will be highest in the Suez and Persian Gulf. Here it reaches 1.03 g/cm³. In the warm and salty waters of the northwestern Indian Ocean, the figure drops to 1.024 g/cm³. And in the freshened northeastern part of the ocean and in the Bay of Bengal, where there is a lot of precipitation, the indicator is the lowest - about 1.018 g / cm³.

The density of fresh water is lower, which is why staying on the water in rivers and other fresh water bodies is somewhat more difficult.

Properties 4 and 5. Transparency and color

If you collect sea water in a jar, it will seem transparent. However, with an increase in the thickness of the water layer, it acquires a bluish or greenish tint. The change in color is due to 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. When there is a high concentration of phytoplankton in ocean water, it becomes blue-green or green in color. This is due to the fact that phytoplankton absorbs the red part of the spectrum and reflects the green part.

The transparency of ocean water indirectly depends on the amount of suspended particles in it. In the field, transparency is determined with a Secchi disk. A flat disk, the diameter of which does not exceed 40 cm, is lowered into the water. The depth at which it becomes invisible is taken as an indicator of transparency in the area.

Properties 6 and 7. Sound propagation and electrical conductivity

Sound waves can travel thousands of kilometers under water. The average propagation speed is 1500 m/s. This indicator for sea water is higher than for fresh water. The sound always deviates slightly from the straight line.

It has a higher electrical conductivity than fresh water. The difference is 4000 times. It depends on the number of ions per unit of water volume.

Instruction

The level of average salinity of the World Ocean is 35 ppm - this figure is most often called in statistics. A slightly more accurate value, without rounding: 34.73 ppm. In practice, this means that about 35 g of salt should be dissolved in each liter of theoretical ocean water. In practice, this value varies quite a lot, since the World Ocean is so huge that the waters in it cannot quickly mix and form a space that is homogeneous in terms of chemical properties.

The salinity of ocean water depends on several factors. First, it is determined by the percentage of water evaporating from the ocean and precipitation falling into it. If there is a lot of precipitation, the level of local salinity drops, and if there is no precipitation, but the water evaporates intensively, then salinity rises. Therefore, in the tropics, in certain seasons, the salinity of the waters reaches record values for the planet. The most part of the ocean is the Red Sea, its salinity is 43 ppm.

At the same time, even if the salt content on the surface of the sea or ocean fluctuates, usually these changes practically do not affect the deep layers of water. Surface fluctuations rarely exceed 6 ppm. In some areas, the salinity of the water is reduced due to the abundance of fresh rivers flowing into the seas.

The salinity of the Pacific and Atlantic oceans is slightly higher than the rest: it is 34.87 ppm. The Indian Ocean has a salinity of 34.58 ppm. The Arctic Ocean has the lowest salinity, and the reason for this is the melting of polar ice, which is especially intense in the Southern Hemisphere. The currents of the Arctic Ocean also affect the Indian Ocean, which is why its salinity is lower than that of the Atlantic and Pacific Oceans.

The farther from the poles, the higher the salinity of the ocean, for the same reasons. However, the saltiest latitudes are between 3 and 20 degrees in both directions from the equator, not the equator itself. Sometimes these "bands" are even said to be salinity belts. The reason for this distribution is that the equator is a zone of constant heavy torrential tropical rains that desalinate water.

67 Movement of water in the oceans Sea currents

Sea currents are the gradual movements of water masses in the oceans and seas, due to various forces (gravitational, friction and tidal forces). They play a significant role in life. World oceans and navigation; encourage the exchange of water masses, changes in coasts (destruction, alluvium of new land), shallowing of port water areas, ice transfer, etc.; great influence on the climate of different parts of the globe: for example, systems e. The North Atlantic Current moderates the climate. Europe. Sea currents differ: by origin - sea currents caused by wind friction on the sea surface (wind currents), uneven distribution of water temperature and salinity (current density), level slope (runoff currents), etc.; according to the degree of stability - stable, changing, temporary, periodic (for example, seasonal currents that change direction under the influence of monsoons) according to placement - surface, subsurface, intermediate, deep, near-bottom; according to physical and chemical properties - warm, cold, desalinated, saline.

The direction of sea currents is affected by rotation. The land that deflects currents into. Northern hemisphere - to the right, c. South - left

The main surface currents arise under the influence of the trade winds blowing over the oceans all year round.

Consider currents. Pacific Ocean. The current, arising under the influence of the northeast trade wind, forms an angle of 45 ° with it, deviating to the right of the wave of the prevailing wind direction. Therefore, the current goes from east to west of the equator, a little north of it. This current creates a northeast trade wind. They call her. Northern trade wind.

The southeast trade wind forms. The south trade wind current, which deviates from the direction of the trade wind to the left by 45 °. It has the same direction as the previous one, from east to west, but passes south of the equator.

Both. The trade wind (equatorial) currents, running parallel to the equator, reach the eastern coast of the continents and branch, with one jet returning along the coast to the north, and the second to the south. Southern branch. North. The trade wind and the northern branch. South. Passat flow. They walk towards each other. Having met, they merge and through the zone of equatorial calm they go from west to east, forming an equatorial countercurrent.

Right branch. North. The trade wind current goes north along the eastern coast of the mainland as a result of rotation. On Earth, it gradually deviates from the coast and, near the 40th parallel, turns east into the open ocean. Here it is picked up by the southwest winds and forced to go in the direction from west to east. Having reached the western coast of the mainland, the current forks, its right branch goes south, deviating by rotation. Lands to the right, and therefore moves away from the shore. Having reached. The northern trade wind (equatorial) current, this branch merges with it and forms a closed northern equatorial circle of currents.

The left branch of the current is directed to the north, deflected by rotation. Land to the right, pressed against the western coast of the mainland and goes along it

Northeast winds blowing from the circumpolar space also create a current. She, carrying very cold water, goes south along the eastern shores of the mainland. Eurasia

B. Southern hemisphere left branch. South. The trade wind current heads south along the eastern shore. Australia, rotation. The land deviates to the left and is pushed away from the shore. At the 40th parallel, this branch of the current returns to the open ocean, jumps up with northwest winds and goes from west to east. On the western shores. America forks. The left branch returns along the line. Rega mainland to the north. Deviating rotation. Lands to the left, this current departs the ox shore and joins with. South trade wind current, forming the southern equatorial ring of currents. The right branch I past the southern tip. America runs east into the neighboring ocean.

Especially terrible are the waves that arise from earthquakes and volcanic eruptions, when the waters fall on the shore. Waves of this origin are called tsunamis.

As a result of action. moon to the surface. The oceans are ebbs and flows. Very high tides occur in the bay. Saint-Malo in. France - up to 15 m. At the top of Filele Bay, the tide height can reach 18 m.

In the southern part. Atlantic Ocean high tides - up to 12-14 m - can be observed off the coast. Patagonia north of the entrance to. Strait of Magellan

In the Pacific the highest tides are in. Sea of Okhotsk off the coast. Russia

In the Indian Ocean, high tides occur along the western shores. India (up to 12 m)