general characteristics water masses
Definition 1
Water mass is a large volume of water, which has its own temperature, salinity, transparency, density, and the amount of oxygen it contains.
A distinctive feature of the water mass from the air mass is vertical zoning.
Between the water masses there are zones of the World Ocean fronts, zones of division and transformation zones that separate them from each other and are traced along the increasing vertical and horizontal gradients of the main indicators.
The characteristics of water masses are not constant and are subject to both seasonal and long-term fluctuations.
When moving from the formation area, water masses are transformed and mixed with the surrounding waters, due to changes in the conditions of heat and water balances.
Water masses can be primary and secondary. The primary ones are those water masses, signs of which are formed directly under the influence of the atmosphere.
Secondary water masses are formed by mixing primary ones, therefore they have more homogeneous features.
Primary water masses are surface and in the vertical structure of the World Ocean are located to a depth of 150-200 m.
The depth of subsurface waters formed by primary and secondary water masses ranges from 200 m to 400-500 m.
Intermediate water masses are also primary and secondary water masses in a vertical structure located at a depth of 400-500 m to 1000-1500 m.
There are also deep water masses, which are secondary and are located at a depth of up to 2500-3000 m.
Secondary bottom water masses in the vertical structure are located at a depth below 3000 m.
Each ocean has water masses that are unique to them.
In general, experts distinguish five types of water masses that form in the surface structural zone:
- equatorial;
- tropical, subdivided into northern tropical and southern tropical, the modification of which is the waters of the Arabian Sea and the Bay of Bengal;
- northern and southern subtropical;
- subpolar, where subarctic and subantarctic are distinguished;
- polar water masses, including Antarctic and Arctic water masses.
The World Ocean and Its Thermal Regime
Total solar radiation is the main source of heat supplied to the surface of the World Ocean.
Waters of rivers, "breathing" of continents, sea currents and prevailing winds are additional sources of heat redistribution.
The surface of the World Ocean, which occupies 71% of the Earth's surface, is a huge heat accumulator, since water is the most heat-retaining body, and it acts as a thermoregulator of the Earth.
On average, the surface water temperature is 3 degrees higher than the average annual air temperature.
The surface water temperature in the Northern Hemisphere is also 3 degrees higher than in the Southern Hemisphere.
Very little heat is transferred to the depth, since water has low thermal conductivity.
Remark 1
Thus, the World Ocean is a cold sphere with an average temperature of +4 degrees.
Due to the zoning, the surface water temperature varies from the equator to the poles of the planet. The farther from the equator, the lower the surface water temperature becomes.
The highest surface water temperatures are observed in the equatorial region of the planet and are +26 degrees.
In temperate and tropical latitudes, there is a violation of the zonal regularity of temperature.
There are warm currents in the tropical zone in the western part of the oceans, so the water temperature in these areas will be 5-7 degrees higher compared to the eastern regions, where cold currents pass.
In temperate latitudes, the surface water temperature decreases towards the poles. And again, currents violate this pattern in the Northern Hemisphere.
Thanks to warm currents, the eastern part of the oceans has a positive temperature all year round, while the cold currents in the western oceans lead to freezing of water - in the Atlantic Ocean water freezes north of the Nova Scotia Peninsula, and in the Pacific Ocean freezing occurs north of the Korean Peninsula.
In cold high latitudes, the water temperature during the polar day reaches 0 degrees, and in winter under the ice it is -1.5 ... -1.7 degrees.
In spring, water warming slows down, because a lot of heat is spent on melting ice. Temperature fluctuations of water throughout the day are insignificant everywhere and do not exceed 1 degree.
All oceans have two main layers vertically, with the exception of high latitudes - a warm surface layer and a thick cold layer extending to the bottom.
Between these layers is the main thermocline, where a sharp decrease in temperature by 10-12 degrees occurs.
In the surface layer, temperature equalization occurs due to convection.
In polar and subpolar latitudes, the vertical temperature is distributed differently: to a depth of 100 m, there is a cold upper thin layer with a temperature of 0 ... -1.5 degrees. This desalinated layer is formed due to the melting of continental and river ice.
To a depth of 500-800 m, the temperature rises by an average of 2 degrees. This happens as a result of the influx of saltier and denser waters from temperate latitudes. Then the temperature drops again and reaches negative values \u200b\u200bat the bottom.
In the Arctic basin, as experts note, a huge water mass is formed from a depth of 800-1000 m, which has a negative temperature from -0.4 to -0.9 degrees to the bottom.
Vertical changes in water temperature strongly affect a number of natural processes and organic life of the inhabitants of the oceans.
Of all the oceans of the planet, the warmest is the Pacific Ocean, with an average surface water temperature of + 19.1 degrees. The coldest is the Arctic Ocean, covered with ice, except for the Norwegian and partly the Barents seas.
The oceans are a living environment
Living organisms in the World Ocean exist from the surface to the very bottom, the concentration of living matter is confined to the water-surface and bottom layers.
Due to favorable conditions, the ocean is home to a wide variety of bacteria, three quarters of animals and half flora planets.
The inhabitants of the ocean, based on their lifestyle, are divided into three groups - nekton, plankton, benthos.
Representatives of nekton are fish, pinnipeds, whales, sea snakes, turtles, dolphins, squids, etc.
Phytoplankton and zooplankton are combined into the plankton group - these are small plants and animals that are passively carried by water.
Phytoplankton include microscopic algae of the upper illuminated layer of water, which are a source of oxygen and an important link in the food chain.
Zooplankton are represented by worms, small crustaceans, jellyfish, crustaceans and some molluscs. Their food is phytoplankton, and zooplankton, in turn, is a food base for fish and cetaceans.
The benthos group is the inhabitants of the bottom - some of them are corals, mollusks, echinoderms, algae, they never separate from it, while other representatives of this group can leave the bottom - for example, flounder, rays.
Benthos inhabits the continental shelf, because it receives the bulk of the organic remains.
The total biomass is 35 billion tons - the share of animals is 32.5 billion tons, the share of algae is 1.7 billion tons.
The entire mass of the waters of the World Ocean is conventionally divided into surface and deep. Surface waters - a layer 200-300 m thick - are very heterogeneous in terms of natural properties; they can be called oceanic troposphere.The rest of the waters - oceanic stratosphere,constituting the main mass of waters, more homogeneous.
Surface waters are a zone of active thermal and dynamic interaction
ocean and atmosphere. In accordance with zonal climatic changes, they are subdivided into different water masses, primarily by their thermohaline properties. Water masses- These are relatively large volumes of water that form in certain zones (foci) of the ocean and have stable physical, chemical and biological properties for a long time.
Lyubushkin
Allocate five typeswater masses: equatorial, tropical, subtropical, subpolar and polar.
Equatorial water masses(O - 5 ° N) form inter-trade countercurrents. They have constantly high temperatures (26 - 28 ° C), a clearly pronounced layer of temperature jump at a depth of 20 - 50 m, low density and salinity - 34 - 34.5% 0, low oxygen content - 3 - 4 g / m 3, a slight saturation with life forms. The rise of water masses prevails. In the atmosphere above them there is a belt of low pressure and calm.
Tropical water masses(5 - 35 ° N sh. and 0-30 ° S. sh.) are distributed along the equatorial periphery of subtropical baric maxima; they form trade winds. The temperature in summer reaches +26 ... + 28 ° С, in winter it drops to +18 ... +20 ° С, and it differs near the western and eastern coasts due to currents and coastal stationary upwellings and downwellings. Upwelling(eng. iryueShpd- surfacing) - the ascending movement of water from a depth of 50-100 m, generated by off-set winds off the western coasts of the continents in a strip of 10-30 km. Having a low temperature and, therefore, a significant oxygen saturation, deep waters rich in biogenic and mineral substances, entering the surface illuminated zone, increase the productivity of the water mass. Downwellings- downdrafts off the eastern coasts of the continents due to the surge of water; they carry heat and oxygen down. The temperature jump layer is expressed throughout the year, salinity 35-35.5% 0, oxygen content 2-4 g / m 3.
Subtropical water massespossess the most characteristic and stable properties in the "core" - circular areas bounded by large currents. The temperature during the year varies from 28 to 15 ° C, there is a layer of temperature jump. Salinity 36-37% o, oxygen content 4 - 5 g / m 3. In the center of the gyres, the waters sink. In warm currents, subtropical water masses penetrate into temperate latitudes up to 50 ° C. sh. and 40-45 ° S. sh. These transformed subtropical water masses occupy here almost entirely the waters of the Atlantic, Pacific and Indian oceans. As they cool, subtropical waters give off a huge amount of heat to the atmosphere, especially in winter, playing a very significant role in planetary heat exchange between latitudes. The boundaries of subtropical and tropical waters are very arbitrary, therefore
some oceanographers combine them into one type of tropical waters.
Subpolar- subarctic (50 - 70 ° N) and subantarctic (45 - 60 ° S) water masses. Typical for them is a variety of characteristics both by seasons of the year and by hemispheres. The temperature in summer is 12-15 ° С, in winter 5 - 7 ° С, decreasing towards the poles. There is practically no sea ice, but there are icebergs. The temperature jump layer is expressed only in summer. Salinity decreases from 35 to 33% o towards the poles. The oxygen content is 4-6 g / m 3, so the waters are rich in life forms. These water masses occupy the North Atlantic and Pacific Ocean, penetrating in cold currents along the eastern coasts of the continents to temperate latitudes. In the southern hemisphere, they form a continuous zone south of all continents. In general, this is the western circulation of air and water masses, a strip of storms.
Polar water massesin the Arctic and around Antarctica, they have low temperatures: in summer about 0 ° C, in winter -1.5 ... -1.7 ° C. Brackish sea and fresh continental ice and their fragments are permanent here. There is no temperature jump layer. Salinity 32-33% 0. The maximum amount of oxygen is dissolved in cold waters - 5 - 7 g / m 3. On the border with subpolar waters, a sinking of dense cold waters is observed, especially in winter.
Each water mass has its own focus of formation. When water masses with different properties meet, oceanological fronts, or convergence zones (lat. concomitantly- converge). They usually form at the junction of warm and cold surface currents and are characterized by a sinking of water masses. There are several frontal zones in the World Ocean, but the main ones are four, two each in the northern and southern hemispheres. In temperate latitudes, they are expressed off the eastern coasts of the continents at the boundaries of the subpolar cyclonic and subtropical anticyclonic gyres with their respective cold and warm currents: near Newfoundland, Hokkaido, the Falkland Islands, and New Zealand. In these frontal zones, hydrothermal characteristics (temperature, salinity, density, current velocities, seasonal temperature fluctuations, sizes of wind waves, amount of fog, cloudiness, etc.) reach extreme values. To the east, due to the mixing of waters, the frontal contrasts are blurred. It is in these zones that frontal cyclones of extratropical latitudes originate. Two frontal zones exist on both sides of the thermal equator off the western shores of the motherland.
coves between tropical relatively cold waters and warm equatorial waters of inter-trade countercurrents. They are also distinguished by high values \u200b\u200bof hydrometeorological characteristics, high dynamic and biological activity, and intense interaction between the ocean and the atmosphere. These are areas of origin of tropical cyclones.
Is in the ocean and divergence zones (lat. c ^^ Ve ^ §en (o- deviate) - zones of divergence of surface currents and the rise of deep waters: at the western coasts of temperate continents and above the thermal equator at the eastern coasts of the continents. Such zones are rich in phyto- and zooplankton, are distinguished by increased biological productivity, and are areas of effective fishing.
The depth of the oceanic stratosphere is divided into three layers, differing in temperature, illumination and other properties: intermediate, deep and bottom waters. Intermediate waters are located at depths from 300-500 to 1000-1200 m. Their thickness is maximum in polar latitudes and in the central parts of anticyclonic gyres, where water subsidence prevails. Their properties are somewhat different depending on the breadth of distribution. General transfer
these waters are directed from high latitudes towards the equator.
Deep and especially bottom waters (the thickness of the latter layer is 1000-1500 m above the bottom) are distinguished by high uniformity (low temperatures, oxygen richness) and a slow speed of movement in the meridional direction from polar latitudes to the equator. Especially widespread are the Antarctic waters, "sliding" from the continental slope of Antarctica. They not only occupy the entire southern hemisphere, but also reach 10-12 ° N. sh. in the Pacific Ocean, up to 40 ° N. sh. in the Atlantic and to the Arabian Sea in the Indian Ocean.
From the characteristics of water masses, especially surface ones, and currents, the interaction of the ocean and the atmosphere is clearly visible. The ocean provides the atmosphere with the bulk of the heat, converting the sun's radiant energy into thermal energy. The ocean is a huge distiller that supplies the land with fresh water through the atmosphere. The heat entering the atmosphere from the oceans causes different atmospheric pressures. The difference in pressure creates wind. It causes excitement and currents that transfer heat to high latitudes or cold to low latitudes, etc. The processes of interaction between the two shells of the Earth - the atmosphere and the oceanosphere - are complex and diverse.
The water masses of the World Ocean can be divided into types characterized by certain properties or a certain ratio of various characteristics. The name of each water mass reflects the region of formation (source) and the way of its movement. For example, Antarctic bottom water is generated in various areas around the Antarctic continent and is found at the bottom over large areas of the ocean. Water masses are formed either as a result of thermohaline changes due to the interaction of the sea and the atmosphere, or as a result of mixing of two or more waters. After formation, the water mass shifts to the horizon determined by its density, depending on the vertical distribution of the density of the surrounding water, and gradually mixing or interacting with the atmosphere (if the water mass spreads near the surface or on horizons close to the surface), it loses its characteristic feature (or features), which she acquired in the area of \u200b\u200bformation.
The main water masses of the World Ocean are formed as a result of thermohaline changes. Such water masses have an extremum in one or many characteristics. The layer in which this extreme is observed (the depth of the layer is determined by the density of the water) is called the middle layer. This layer can be detected by studying the vertical distribution of typical properties of V. m.
The largest part of the surface and subsurface water masses is the central water masses, which are found in temperate latitudes in both hemispheres. They are characterized by high salinity and rather high temperatures and can be subdivided into such subtypes as Western and Eastern Central Water Masses. These are precisely the water masses that are the source of the middle layer with a low maximum salinity (subtropical countercurrent), which forms as a result of the subsidence of surface waters in the zones of subtropical convergence (35-40 ° N and S) in most tropical regions of the ocean. Equatorial water is located between the central water masses of the northern and southern hemispheres. This water mass is well developed in the Pacific and Indian Oceans, but it is not in the Atlantic Ocean.
Towards the poles, the central water masses are cooled, which is associated with the melting of ice and the temperature contrast between water and the atmosphere. Between the polar surface water masses and deep waters, there are waters of the intermediate zone - subarctic and subantarctic surface waters. At the junction of the water masses of the intermediate zone, the waters descend along the convergence zone. This zone, or the polar front, can be considered as an area of \u200b\u200bformation of intermediate water masses of the World Ocean. They are cold, have low salinity and separate the upper warm water sphere from the lower cold one. In the Atlantic Ocean, the most common intermediate water mass is the Antarctic intermediate water, which forms within the southern polar front; it can be traced by the "kernel method" up to 20 ° N. sh. To the north of this latitude, there is a middle layer with a mild salinity minimum.
Subarctic intermediate water is found in more northern latitudes, but it is much less pronounced and does not spread as widely as Antarctic intermediate water.
Due to the shallowness of the Bering Strait, circulation between the Arctic Ocean and the North Pacific is limited; therefore, the subarctic intermediate water in the Pacific Ocean has a small distribution. However, near the coast of Russia, the waters sink and the intermediate water mass is formed, very similar to the subarctic one; since this body of water is of non-Arctic origin, it is called the North Pacific Intermediate Water.
Deep and bottom waters are formed in the polar regions, most actively - around the Antarctic continent and in areas adjacent to South Greenland. The influence of the Arctic Basin on the deep-water circulation of the World Ocean is insignificant due to the separation of the depths of the Arctic Basin by underwater ridges - rapids. It is assumed that the source of most of the deep and bottom waters is the Atlantic sector of the Southern Ocean (Weddell Sea). Strong deep-sea circulation leads to the fact that the influence Atlantic Ocean felt in most parts of the oceans. The Pacific Ocean does not have large sources of deep water, and therefore the flow below 2000 m is probably weak. The Indian Ocean has a complex system of deep waters that depends more on the mixing of many other Water masses than on the formation of types of Water masses as a result of thermohaline changes.
LESSON 9
Topic: Water masses and their properties
target: to update knowledge about the properties of the waters of the World Ocean; to formulate knowledge about water masses and their characteristic features; promote understanding of the patterns of movement of ocean currents; to improve the ability to work with thematic maps of the atlas; develop research skills, the ability to define concepts, make generalizations, draw analogies, establish causal relationships, draw conclusions; educate independence, responsibility, attentiveness.
Equipment: physical map of the world, textbooks, atlases, contour maps.
Lesson type: combined.
Expected results: students will be able to give examples of water masses of different properties, compare their properties; show on the map the largest warm and cold surface currents and explain their movements.
During the classes
ІІ ... Updating basic knowledge and skills
Check homework
Working in pairs
Reception "Mutual questioning", "Mutual check"
Students exchange notebooks and decide, prepared at home, test tasks, check the correctness of their implementation with each other.
Reception "Why Much"
Why do air temperatures change from the equator to the poles?
Why do air masses have different properties?
Why are air masses constantly moving?
Why trade winds have northeast and southeast
direction?
Why are monsoons formed?
Why is the amount of precipitation near the equator, and in tropical latitudes
Reception "Problem issue"
Why isotherms on climate maps change their latitudinal extent to meandering?
III ... Motivation training and cognitive activities
Reception "Practicality of theory"
Now you know that the climate is formed under the influence of three main climate-forming factors that interact with each other and create conditions for the formation of various climatic conditions on the ground.
In the course of studying the characteristics of climate-forming factors, we have repeatedly noted the role of air masses that form over the oceans and bring moisture to the continents. In order to understand what role the oceans play in shaping the climate and life of the planet as a whole, we will learn more about the main component of the nature of the World Ocean - its water masses.
І V. Learning new material
1 Formation of the concept of "water masses"
The task. Remember what air masses are and their types. Similarly to the concept of air masses formed in the air ocean, water masses are distinguished in the World Ocean.
Water masses - large volumes of water generated in certain parts of the ocean and differ from each other:
Temperature,
Salinity,
Density,
Transparency,
The amount of oxygen and other properties.
According to the regions of their formation, the following types of water masses are distinguished:
Polar,
Moderate,
Tropical,
Equatorial, which in turn are divided into subtypes:
Coastal
Intraoceanic.
Water masses also change with depth: they distinguish
superficial
intermediate,
deep
bottom water masses.
The thickness of the layer of surface water masses reaches 200-250 m. Being in constant contact with the atmosphere, they change most of their characteristics during the year, actively moving in space.
The main properties of water masses are temperature and salinity. .
Conclusion 1... In the World Ocean, significant volumes of water are formed with certain properties - water masses. The properties of water masses change depending on the depth and place of their formation.
2 Updating knowledge about the basic properties of water masses
Working with the map "Average annual salinity of waters on the surface of the World Ocean"
The task
1) Determine the regularities of the distribution of the salinity of the surface waters of the World Ocean.
2) Explain the factors behind this distribution.
The average salinity of ocean waters is 35 ‰.
In equatorial latitudes, salinity is slightly reduced due to the intensity of the desalination effect of atmospheric precipitation.
In subtropical and tropical latitudes, salinity is increased - here evaporation prevails over precipitation, increases the concentration of salts.
In temperate latitudes, salinity is close to average.
Salinity decreases in high latitudesdue to low evaporation, melting sea \u200b\u200bice, river runoff (in the Northern Hemisphere).
The salinity of the surface waters of the oceans under the influence of a number of factors varies within fairly wide ranges - from 31 ‰ in the Gulf of Guinea to 42 ‰ in the Red Sea... At depths over several hundred meters, it almost everywhere approaches 34.8 ‰, and from a depth of 1500 m to the bottom it is 34.5 ‰.
Conclusion 2. The salinity of the surface water masses of the ocean primarily depends on climatic conditions that vary with latitude. The distribution of salinity is also influenced by currents and the degree of closedness of sea basins, especially for inland seas.
The task... Analyze the map of the indicators of the average annual temperature of the surface waters of the World Ocean and explain the reasons for the changes in these indicators.
In the equatorial latitudes, the surface water temperature throughout the year is 27-28 ° C.
In tropical zones, the average is 20-25 ° C.
However, it is in these latitudes that the highest average annual temperatures were recorded (in the Persian Gulf - 37 ° С, in the Red Sea - 32 ° С).
The temperate latitudes are characterized by seasonal changes in water temperatures, and the average annual gradually decreases towards the poles from 10 to 0 ° С.
In the polar latitudes, the temperature of the ocean waters during the year varies from 0 to -2 ° C. At a temperature of about -2 ° C, sea \u200b\u200bwater medium salinity freezes (the higher the salinity, the lower the freezing point).
Consequently, the temperature of the surface water layer depends on the climate and decreases from the equator to the poles.
The average temperature of the surface layer of ocean waters is 17-54 ° C. With depth, the water temperature drops rather quickly to a depth of 200 m, from 200 to 1000 m - more slowly. At depths of more than 1000 m, the temperature is approximately 2 ... + 3 ° C.
The average temperature of the entire mass of water in the ocean is 4 ° C.
Ocean water has a huge heat capacity of 1 m3 of water, cooling by 1 ° C, it can heat more than 3300 m3 of air by 1 ° C.
Conclusion 3... The temperature distribution of the surface waters of the World Ocean has a zonal character. Water temperature decreases with depth.
3 Currents in the World Ocean
Even in ancient times, people established that thanks to the wind that blows over the sea, not only waves arise, but also currents, which play a huge role in the process of heat distribution on Earth.
Ocean currents - horizontal displacement of huge water masses in a certain direction over long distances.
The task. Compare climatic and physical maps, determine the relationship between constant winds and surface currents.
Conclusion 4. The direction of the largest sea currents almost coincides with the main air currents of the planet. The most powerful surface currents are formed by two types of winds: westerly, which blow from west to east, and trade winds, blowing from east to west.
By the properties of water, warm and cold currents are distinguished. the interaction of atmospheric flows leads to the formation of a system of gyres of surface currents.
V. Consolidation of the studied material
Reception "Geographic workshop" (subject to availability of study time)
The task... Using the maps of salinity and temperature of surface waters and the text of the textbook, make a characteristic of the water masses. Enter the results in the table.
Reception "Blitzopros"
What are water masses? Are the types of water masses distinguished in the World Ocean?
What determines the distribution of the salinity of the waters of the World Ocean?
How and why does the water temperature change from the equator to the poles and with depth?
Give examples of currents whose names coincide with the names of the winds that formed.
VІ ... ANDtog lesson, Preflection
What new discoveries have you made for yourself today in the lesson?
VІІ ... HOMEWORK
1. Develop an appropriate paragraph of the textbook.
2. Mark on outline map the largest warm and cold currents of the World Ocean.
3. Get together in groups for the next lesson.
4. Conduct research: "Interaction of the World Ocean, atmosphere
and sushi, its consequences ”. Form the results in the form of a diagram (Or a picture) with appropriate comments.
- These are large volumes of water that form in certain parts of the ocean and differ from each other temperature, salinity, density, transparency, the amount of oxygen contained and many other properties. In contrast, it is of great importance in them.
AT depending on depth the following types of water masses are distinguished:
Surface water masses . They go deep 200-250 m... The water temperature and salinity often change here, 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... In this type of water masses the highest content of plankton and fish.
Intermediate water masses ... They go deep 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 may be before 5000 m... Their formation is associated with mixing of surface and intermediate water masses, polar and tropical masses. They move vertically very slowly, but horizontally - at a speed of 28 m / h.
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 the depth, but also by origin... In this case, the following types of water masses are distinguished:
Equatorial water masses ... They are well warmed up by the sun, their temperature changes by no more than 2 ° C and is 27 - 28 ° C. They are desalinated by abundant atmospheric precipitation and flowing into the ocean at these latitudes, therefore the salinity of these waters is lower than in tropical latitudes.
Tropical water masses ... They are also well warmed up by the sun, but the water temperature here is lower than in, and is 20-25 ° C. Seasonally, the temperature of the waters in tropical latitudes changes by 4 °. The temperature of the waters of this type of water masses big influence render ocean currents: the western parts of the oceans, where warm currents come from the equator, are warmer than the eastern ones, since cold currents come there... The salinity of these waters is much higher than the equatorial ones, since here, as a result of the descending 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 ... According to the seasons, the temperature of the waters of these latitudes differs by 10 °: in winter the water temperature fluctuates from 0 ° to 10 ° С, and in summer it changes from 10 ° to 20 ° С. These waters are already characterized by the change of seasons, but it comes later than on land, and is not so pronounced. The salinity of these waters is lower than that of tropical waters, since atmospheric precipitation, rivers flowing into these waters, and entering these latitudes have a desalination effect. Temperate water masses are also characterized by temperature differences between the western and eastern parts of the ocean: the western parts of the oceans are cold, where cold currents pass, 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, which forms huge ice spaces. In the Southern Hemisphere, in areas of polar water masses, they go into temperate latitudes much further than in the Northern. The salinity of polar water masses is low, since floating ice has a strong desalination effect.
Between different kinds water masses differing in origin, there are no clear boundaries, but there are transition zones... They are most pronounced in places where warm and cold currents meet.
Water masses actively interact with: they give it moisture and heat and absorb carbon dioxide from it, release oxygen.
The most characteristic properties of water masses are and.