Water masses and their properties. Water masses How water masses are formed

Water masses- these are large volumes of water formed in certain parts of the ocean and differing from each other in temperature, salinity, density, transparency, amount of oxygen contained and many other properties. Unlike air masses, they great importance has vertical zoning. Depending on the depth, the following types of water masses are distinguished:

Surface water masses. They are located to a depth of 200-250 m. Here the water temperature and salinity often change, since these water masses are formed under the influence of precipitation and the influx of fresh continental waters. Waves and horizontal ocean currents form in surface water masses. This type of water mass contains the highest content of plankton and fish.

Intermediate water masses. They are located to a depth of 500-1000 m. Basically, this type of mass is found in the tropical latitudes of both hemispheres and is formed under conditions of increased evaporation and a constant increase in salinity. Deep water masses. Their lower limit can reach up to 5000 m. Their formation is associated with the mixing of surface and intermediate water masses, polar and tropical masses. They move vertically very slowly, but horizontally at a speed of 28 m/hour.

Bottom water masses. They are located in the World Ocean below 5000 m, have constant salinity and very high density.

Water masses can be classified not only depending on depth, but also by origin. In this case, the following types of water masses are distinguished:

Equatorial water masses. They are well warmed by the sun, their temperature varies by season by no more than 2° and is 27 - 28°C. They are desalinated by heavy precipitation and rivers flowing into the ocean at these latitudes, so the salinity of these waters is lower than in tropical latitudes.

Tropical water masses. They are also well warmed by the sun, but the water temperature here is lower than in equatorial latitudes and amounts to 20-25°C. Seasonally, the temperature of waters in tropical latitudes varies by 4°. The temperature of the waters of this type of water mass is greatly influenced by ocean currents: the western parts of the oceans, where warm currents from the equator arrive, are warmer than the eastern parts, since cold currents arrive there. The salinity of these waters is much higher than that of the equatorial ones, since here, as a result of downward air currents, high pressure is established and little precipitation falls. Rivers also do not have a desalination effect, since there are very few of them in these latitudes.

Moderate water masses. By season, the water temperature of these latitudes differs by 10°: in winter the water temperature ranges from 0° to 10°C, and in summer it varies from 10° to 20°C. These waters are already characterized by a change of seasons, but it occurs later than on land and is not so pronounced. The salinity of these waters is lower than that of tropical waters, since the desalination effect is exerted by precipitation, rivers flowing into these waters, and icebergs entering these latitudes. Temperate water masses are also characterized by temperature differences between the western and eastern parts of the ocean: the western parts of the oceans, where cold currents pass, are cold, and the eastern regions are warmed by warm currents.

Polar water masses. They form in the Arctic and off the coast of Antarctica and can be carried by currents to temperate and even tropical latitudes. Polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. In the Southern Hemisphere in areas of polar water masses sea ​​ice they extend into temperate latitudes much further than in the North. The salinity of polar water masses is low, since floating ice has a strong desalination effect.

Between different types water masses differing in origin do not have clear boundaries, but there are transition zones. They are most clearly expressed in places where warm and cold currents meet. Water masses actively interact with the atmosphere: they give moisture and heat to it and absorb it from it carbon dioxide, release oxygen. The most characteristic properties of water masses are salinity and temperature.

Characteristics of water masses

Water masses are classified not only depending on depth, but also by origin. Regarding this they are:

• equatorial,
• tropical,
• moderate,
• polar.

Equatorial water masses are formed near the equator, so they are well heated by the Sun. The water temperature is +27, +28 degrees and varies by seasons only by 2 degrees. Heavy rainfall and rivers flowing into the ocean greatly desalinate the water, so the salinity of equatorial waters is lower compared to tropical latitudes.

The water masses of tropical latitudes are also well heated by the Sun, but their temperature is lower and is +20, +25 degrees, and by season it changes by 4 degrees. Currents have a great influence on water temperature. Warm currents coming from the equator are characteristic of the western parts of the ocean, so the water here will be warmer. Cold currents come to the eastern part of the ocean and reduce the water temperature.

In tropical latitudes, downward air currents dominate, resulting in high atmospheric pressure with little precipitation. There are few rivers here and their desalination effect is insignificant, so the salinity of water in this area is high.

To the north are temperate latitudes, where the formation of moderate water masses occurs. The seasonal distribution of temperatures is clearly visible here, and the difference is 10 degrees. Winter temperatures range from 0 to 10 degrees, and in summer the change occurs from 10 to 20 degrees.

The salinity of temperate water masses is lower than tropical ones, because atmospheric precipitation, rivers flowing into the ocean and icebergs entering these latitudes have a great desalination effect.

The western and eastern parts of the oceans within temperate latitudes also have temperature differences. The western parts of the oceans will be cold, and the eastern parts will be warmed by warm currents.

In the Arctic region and off the coast of Antarctica, polar water masses are formed, which, with the help of currents, are carried to temperate latitudes, sometimes reaching tropical latitudes. A feature of polar water masses is the presence of floating ice, which has a strong desalination effect. Therefore, the salinity of polar water masses is low.

Note 1

There are no clear boundaries between water masses of different origins; there are only transition zones, which are more clearly expressed in those places where warm and cold currents come into contact.

Water masses depending on criteria

Depending on the criteria, different amounts of water masses are allocated.

The Antarctic bottom water mass is the largest in volume in the World Ocean, occupying the bottom layer around the continent. It extends north in the Atlantic Ocean to the 40th parallel north latitude. The meridional section of this water mass shows lower temperature and salinity compared to the waters above. The main place of its formation is the Weddell Sea and the shelf around Antarctica, where conditions favorable for this have formed. The salinity of the Antarctic bottom water mass is 34.6 ppm, and the temperature is -0.4 degrees. From the place of its formation, it slowly moves into the Atlantic, participating in the horizontal circulation of ocean waters;

The second largest volume in the World Ocean is the deep and bottom North Atlantic water mass. Its formation occurs in the winter between Greenland and Iceland. This is where the warm, salty water of the North Atlantic Current mixes with the cold, fresher water of the East Greenland Current. The temperature of this water mass in the area of ​​formation varies with depth from 2.8 to 3.3 degrees, and the salinity also changes from 34.90 to 34.96 ppm. The North Atlantic deep and bottom water mass from the formation area spreads south to a depth of 2000-4000 m on top of the Antarctic bottom water. It is prevented from moving in a northerly direction by the rising ocean floor;

Figure 1. North Atlantic water mass. Author24 - online exchange of student work

Note 2

There are no conditions for the formation of such a water mass in the Pacific Ocean.

Surface water is represented by the Antarctic intermediate water mass, which in the convergence zone spreads to the north to a depth of 1000-1500 m. In the area Atlantic Ocean it is noticeable up to 15 degrees north latitude. Its salinity here is minimal and equal to 33.8 ppm, the temperature is reduced to 2.2 degrees;

For stationary subtropical maxima atmospheric pressure The formation of central water masses is characteristic. Their feature is maximum salinity. Intense convection develops on their peripheries during periods of cooling, as a result of which the central masses increase their thickness in the Pacific Ocean to 200-300 m, and in the Sargasso Sea of ​​the Atlantic Ocean their thickness increases to 900 m;

In the area of ​​the equator, equatorial water masses of 3 oceans are formed - the Pacific, Indian and Atlantic. Due to the fact that a lot of precipitation falls in the equatorial region, these water masses are highly desalinated compared to the central water masses. The equatorial water mass is less pronounced in the Atlantic Ocean because water is transferred from the Southern to the Northern Hemisphere here;

In the formation of deep waters of the Atlantic Ocean, the Mediterranean water mass plays a rather noticeable role, the temperature of which is 13.0-13.6 degrees, and the salinity is 38.4-38.7 ppm. This water mass has a high density, due to which, having flowed through the Strait of Gibraltar, it sinks to a depth of 1000 m and spreads like a fan over the vast expanse of the North Atlantic;

• In the northwestern part Indian Ocean a similar role is played by the Red Sea water mass with a temperature of 23 degrees and a salinity of 40 ppm.

Other types of water masses

The formation of the Antarctic circumpolar water mass involves North Atlantic deep and bottom water rising near Antarctica, to which a certain amount of Antarctic intermediate and bottom water is mixed.

The mixture that is formed rises as an independent water mass into the upper layer of the ocean. It occupies a place between the Antarctic coastal waters and the Antarctic convergence.

Antarctic circumpolar water in the circular transport of water forms a ring that encircles Antarctica.

The upper layer of Antarctic circumpolar water is characterized by divergence of zonal transport, which causes the rise of North Atlantic deep and bottom water in the Antarctic region.

Between the Antarctic convergence and the southern boundary of the central water masses lies the subantarctic water mass. It forms a closed ring in which it moves from west to east. This water mass is the result of the mixing of central water masses with Antarctic intermediate water at their southern peripheries.

In the Northern Hemisphere over a large area Pacific Ocean, north of the 40th parallel, there is a subarctic water mass. It was formed by the processes of cooling and desalination of water in the Bering and Okhotsk seas, as well as in the adjacent part of the ocean.

In the Atlantic, this type of water is formed in small quantities.

Four water masses are present in the Arctic Ocean, and the entire water column has a negative temperature, with only a thin layer of water with a positive temperature.

The active layer of the ocean with desalinated waters and negative temperatures drops to a depth of 200-250 m - this is the surface water mass. In winter, this layer is completely covered by convection, and the temperature drops almost to the freezing point - about -1.7 degrees.

In summer the temperature is just above freezing. The salinity on the surface of this water mass is 31.3-31.5 ppm.

A unique phenomenon in the World Ocean is the warm Atlantic layer, formed from the warm West Spitsbergen Current. In order for this water mass, due to its high density, to sink under surface layer The Arctic Ocean, with its salinity up to 34.75 ppm, is enough for the water to cool to 3-4 degrees.

Then it spreads throughout the ocean at a depth of 200-500 m, and even near the Bering Strait it retains high salinity and a positive temperature of +0.4 degrees.

Deep and bottom water masses are formed in the Greenland Sea.

Note 3

Thus, the water masses that form in certain areas of the World Ocean well reflect the vertical and horizontal zoning, which is the main geographical pattern of the nature of the planet.

Water masses- these are large volumes of water formed in certain parts of the ocean and differing from each other in temperature, salinity, density, transparency, amount of oxygen and other properties. In contrast, , in them, is of great importance. Depending on the depth there are:

Surface water masses. They are formed under the influence of atmospheric processes and influx fresh water from the mainland to a depth of 200-250 m. Here, salinity often changes, and their horizontal transport in the form of ocean currents is much stronger than deep transport. Surface waters contain the highest levels of plankton and fish;

Intermediate water masses. They have a lower limit of 500-1000 m. Intermediate water masses are formed under conditions of increased evaporation and constant increase. This explains the fact that intermediate waters occur between 20° and 60° in the Northern and Southern Hemispheres;

Deep water masses. They are formed as a result of mixing surface and intermediate, polar and tropical water masses. Their lower limit is 1200-5000 m. Vertically, these water masses move extremely slowly, and horizontally they move at a speed of 0.2-0.8 cm/s (28 m/h);

Bottom water masses. They occupy a zone below 5000 m and have constant salinity, very high density, and their horizontal movement is slower than vertical.

Depending on the origin there are following types water masses:

Tropical. They form in tropical latitudes. The water temperature here is 20-25°. The temperature of tropical water masses is greatly influenced by ocean currents. The western parts of the oceans are warmer, where warm currents (see) come from the equator. The eastern parts of the oceans are colder because cold currents come here. Seasonally, the temperature of tropical water masses varies by 4°. The salinity of these water masses is much greater than that of the equatorial ones, since as a result of downward air currents little precipitation is established and falls here;

water masses. In the temperate latitudes of the Northern Hemisphere, the western parts of the oceans are cold, where cold currents pass. The eastern regions of the oceans are warmed by warm currents. Even in the winter months, the water temperature in them ranges from 10°C to 0°C. In summer it varies from 10°C to 20°C. Thus, the temperature of temperate water masses varies by 10°C between seasons. They are already characterized by the change of seasons. But it comes later than on land, and is not so pronounced. The salinity of temperate water masses is lower than that of tropical ones, since the desalination effect is exerted not only by rivers and precipitation that fall here, but also by those entering these latitudes;

Polar water masses. Formed in and off the coast. These water masses can be carried by currents to temperate and even tropical latitudes. In the polar regions of both hemispheres, water cools to -2°C, but still remains liquid. Further decrease leads to the formation of ice. Polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. The ice lasts all year and is in constant drift. In the Southern Hemisphere, in areas of polar water masses, they extend into temperate latitudes much further than in the Northern Hemisphere. The salinity of polar water masses is low, since ice has a strong desalination effect. There are no clear boundaries between the listed water masses, but there are transition zones - zones of mutual influence of neighboring water masses. They are most clearly expressed in places where warm and cold currents meet. Each water mass is more or less homogeneous in its properties, but in transition zones these characteristics can change dramatically.

Water masses actively interact with water: they give it heat and moisture, absorb carbon dioxide from it, and release oxygen.

Just like air space, water space is heterogeneous in its zonal structure. We will talk about what is called water mass in this article. We will identify their main types, and also determine the key hydrothermal characteristics of oceanic waters.

What is the water mass of the World Ocean called?

Oceanic water masses are relatively large layers of oceanic waters that have certain properties (depth, temperature, density, transparency, amount of salts contained, etc.) characteristic of a given type of body of water. The formation of the properties of a certain type of water masses occurs over a long period of time, which makes them relatively constant and the water masses are perceived as a single whole.

Main characteristics of marine water masses

Oceanic water masses in the process of interaction with the atmosphere acquire various characteristics, differing depending on the degree of impact, as well as on the source of formation.

Main zones of water masses of the World Ocean

The complex characteristics of water masses are formed under the influence of not only territorial characteristics in combination with climatic conditions, but also due to the mixing of different water flows. The upper layers of ocean waters are more susceptible to mixing and influence of the atmosphere than the deeper layers of water in the same geographic region. In connection with this factor, the water masses of the World Ocean are divided into two large sections:

Types of waters of the oceanic troposphere

The oceanic troposphere is formed under the influence of a combination of dynamic factors: climate, precipitation, and the tide of continental waters. Due to this surface water have frequent fluctuations in temperature and salinity levels. The movement of water masses from one latitude to another forms the formation of warm and

The greatest saturation of life forms in the form of fish and plankton is observed. Types of water masses in the oceanic troposphere are usually divided according to geographic latitudes with a pronounced climatic factor. Let's name the main ones:

• Equatorial.
• Tropical.
• Subtropical.
• Subpolar.
• Polar.

Characteristics of equatorial water masses

The territorial zonality of equatorial water masses covers a geographical band from 0 to 5 northern latitude. The equatorial climate is characterized by almost uniformly high temperatures throughout the entire calendar year, therefore the water masses of this region are sufficiently warmed up, reaching a temperature of 26-28.

Due to heavy precipitation and the influx of fresh river water from the mainland, equatorial oceanic waters have a small percentage of salinity (up to 34.5‰) and the lowest conditional density (22-23). The saturation of the region's aquatic environment with oxygen also has the lowest rate (3-4 ml/l) due to the high average annual temperature.

Characteristics of tropical water masses

The zone of tropical water masses occupies two bands: 5-35 in the northern hemisphere (north tropical waters) and up to 30 in the southern hemisphere (south tropical waters). They are formed under the influence of climate characteristics and air masses - trade winds.

The summer temperature maximum corresponds to the equatorial latitude, but in winter this figure drops to 18-20 above zero. The zone is characterized by the presence of ascending water flows from a depth of 50-100 meters near the western coastal continental lines and downward flows near the eastern shores of the continent.

Tropical types of water masses have a higher salinity index (35-35.5‰) and conditional density (24-26) than that of the equatorial zone. The oxygen saturation of tropical water flows remains approximately at the same level as that of the equatorial strip, but the saturation with phosphates is higher: 1-2 µg-at/l versus 0.5-1 µg-at/l in equatorial waters.

Subtropical water masses

The temperature during the year in the subtropical water zone can drop to 15. In tropical latitudes, water desalination occurs to a lesser extent than in other climatic zones, since there is little precipitation here, while intense evaporation occurs.

Here the water salinity can reach up to 38‰. Subtropical water masses of the ocean, when cooled in the winter, give off a lot of heat, thereby making a significant contribution to the heat exchange process of the planet.

The boundaries of the subtropical zone reach approximately 45 southern hemispheres and 50 northern latitudes. There is an increase in the saturation of waters with oxygen, and therefore with life forms.

Characteristics of subpolar water masses

As you move away from the equator, the temperature of the water streams decreases and varies depending on the time of year. So, in the territory of subpolar water masses (50-70 N and 45-60 S), in winter the water temperature drops to 5-7, and in summer it rises to 12-15 about S.

Water salinity tends to decrease from subtropical water masses towards the poles. This happens due to the melting of icebergs - sources of fresh water.

Characteristics and features of polar water masses

The localization of polar oceanic masses is the circumcontinental polar northern and southern spaces, thus, oceanologists highlight the presence of Arctic and Antarctic water masses. The distinctive features of polar waters are, of course, the lowest temperature indicators: in summer the average is 0, and in winter 1.5-1.8 below zero, which also affects the density - here it is the highest.

In addition to temperature, low salinity (32-33‰) is also noted due to the melting of continental fresh glaciers. The waters of polar latitudes are very rich in oxygen and phosphates, which has a beneficial effect on the diversity of the organic world.

Types and properties of water masses in the oceanic stratosphere

Oceanologists conventionally divide the oceanic stratosphere into three types:

1. Intermediate waters cover water columns at depths from 300-500 m to 1000 m, and sometimes 2000 m. Compared with the other two types of water masses in the stratosphere, the intermediate layer is the most illuminated, warm and more rich in oxygen and phosphates, and therefore the underwater world is richer in plankton and various types fish Under the influence of the proximity to water flows of the troposphere, in which rapidly flowing water mass predominates, the hydrothermal characteristics and flow speed of water flows in the intermediate layer are very dynamic. The general tendency for the movement of intermediate waters is observed in the direction from high latitudes to the equator. The thickness of the intermediate layer of the oceanic stratosphere is not the same everywhere; a wider layer is observed near the polar zones.
2. Deep waters have a distribution area starting from a depth of 1000-1200 m, and reaching 5 km below sea level and are characterized by more constant hydrothermal data. The horizontal flow of water flows in this layer is much less than intermediate waters and amounts to 0.2-0.8 cm/s.
3. The bottom layer of water is the least studied by oceanologists due to its inaccessibility, because it is located at a depth of more than 5 km from the surface of the water. The main features of the bottom layer are an almost constant level of salinity and high density.

are large volumes of water that form in certain parts of the ocean and differ from each other temperature, salinity, density, transparency, amount of oxygen contained and many other properties. In contrast, , in them, is of great importance.

IN depending on depth The following types of water masses are distinguished:

Surface water masses . They are located to the depth 200-250 m. Here the water temperature and salinity often change, since these water masses are formed under the influence of the influx of fresh continental waters. In surface water masses are formed waves And horizontal. This type of water mass contains the highest content of plankton and fish.

Intermediate water masses . They are located to the depth 500-1000 m. Basically, this type of mass is found in both hemispheres and is formed under conditions of increased evaporation and a constant increase in salinity.

Deep water masses . Their lower limit can reach before 5000 m. Their formation is associated with the mixing of surface and intermediate water masses, polar and tropical masses. They move vertically very slowly, but horizontally at a speed of 28 m/hour.

Bottom water masses . They are located in below 5000 m, have constant salinity and very high density.

Water masses can be classified not only depending on depth, but also by origin. In this case, the following types of water masses are distinguished:

Equatorial water masses . They are well warmed by the sun, their temperature varies by season by no more than 2° and is 27 - 28°C. They are desalinated by heavy precipitation and water flowing into the ocean at these latitudes, so the salinity of these waters is lower than in tropical latitudes.

Tropical water masses . They are also well warmed by the sun, but the water temperature here is lower than in, and is 20-25°C. Seasonally, the temperature of waters in tropical latitudes varies by 4°. The water temperature of this type of water mass is greatly influenced by ocean currents: the western parts of the oceans, where warm currents from the equator come, are warmer than the eastern parts, since cold currents come there. The salinity of these waters is much higher than that of the equatorial ones, since here, as a result of downward air currents, high pressure is established and little precipitation falls. Rivers also do not have a desalination effect, since there are very few of them in these latitudes.

Moderate water masses . By season, the water temperature of these latitudes differs by 10°: in winter the water temperature ranges from 0° to 10°C, and in summer it varies from 10° to 20°C. These waters are already characterized by a change of seasons, but it occurs later than on land and is not so pronounced. The salinity of these waters is lower than that of tropical waters, since the desalination effect is exerted by precipitation, rivers flowing into these waters, and rivers entering these latitudes. Temperate water masses are also characterized by temperature differences between the western and eastern parts of the ocean: the western parts of the oceans, where cold currents pass, are cold, and the eastern regions are warmed by warm currents.

Polar water masses . They form in the Arctic and off the coast and can be carried by currents to temperate and even tropical latitudes. Polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. In the Southern Hemisphere, in areas of polar water masses, they extend into temperate latitudes much further than in the Northern Hemisphere. The salinity of polar water masses is low, since floating ice has a strong desalination effect.

There are no clear boundaries between different types of water masses that differ in origin, but there are transition zones. They are most clearly expressed in places where warm and cold currents meet.

Water masses actively interact with water: they give it moisture and heat and absorb carbon dioxide from it and release oxygen.

The most characteristic properties of water masses are And.