What determines the temperature of ocean water? Seawater Temperature and Salinity What are the differences in ocean water temperature.
In the open ocean, the water is clearer than near the shores, since there are more impurities in the water near the shores. Depending on the type of impurities, water may have a different color. For example, the waters of the Yellow Sea have a yellow tint due to silt of this color, which enters the sea along with the waters of the rivers flowing into it.
Compared to land, water heats up more slowly and cools down more slowly. Its heat capacity is greater. In warm times, ocean water accumulates a huge amount of heat and, cooling in cold times, releases it. Therefore, the World Ocean significantly influences the temperature of land when winds blow from it to the continents.
With depth, the temperature of ocean waters drops and already deeper than 200 m it can be around zero or even lower.
The temperature of the upper layers of the waters of the World Ocean, as well as on land, depends on the latitude of the area. It is much warmer at the equator than at the poles. In temperate zones, water is warmer in summer than in winter. The average temperature of the surface waters of the World Ocean is about +17 °C.
An important property of the ocean is its salinity. In fact, sea water is bitterly salty. Various salts are dissolved in it. Salinity shows how many grams of salts are dissolved in 1 liter of water. Salinity is measured in ppm (‰). The average salinity of the waters of the World Ocean is about 35‰. This means that 35 grams of various salts are dissolved in 1 liter of ocean water.
There are many different substances dissolved in the oceans, but the most common is table salt.
The salinity of ocean waters is not the same everywhere. This is not how the rivers entering the seas influence it. They desalinate nearby waters. Melting ice also makes the water less salty. Currents transport water and affect salinity. Salinity is especially affected by precipitation. Where there is a lot of rain, the salinity is less. In places where there is high temperature and little precipitation, salinity is high, since at high temperatures water evaporates more.
Salinity and temperature affect the density of water. Cold water is heavier than warm water, and saltier water is heavier than less salty water. The different densities of water cause it to move.
The amount of substances dissolved in water affects its freezing point. The more there are, the lower the temperature the water freezes. So on average, ocean water freezes at a temperature of –2 °C.
Living organisms living in the seas and oceans are adapted to a certain salinity.
Gases are also dissolved in water. So the amount of oxygen in water decreases with increasing temperature. Therefore, in warm waters the number of living organisms is less than in relatively colder ones. With depth, the amount of oxygen also decreases.
1. What determines the salinity of ocean waters?
The world ocean, the main part of the hydrosphere, is 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 characteristics.
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 from atmospheric precipitation. Water evaporation occurs more intensely 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 saltier. The salinity of water in the oceans also varies depending on the geographical location, however, in the ocean the mixing of water occurs more intensely than in more closed seas, therefore the difference in the salinity of 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 water temperature in the World Ocean also varies depending on geographic latitude. In tropical and equatorial latitudes, the water temperature can reach +30 °C and above; in the polar regions it drops to -2 °C. 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 land temperature. This heat is transferred to land using 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 partly in temperate latitudes. The resulting ice cover affects the climate of the continents and makes it difficult to use cheap sea transport in the north to transport goods.
4. What is called water mass? Name the main types of water masses. What water masses are found in the surface layer of the ocean?
You will find a 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 others in salinity, temperature, transparency and other characteristics. Water masses vary not only depending on the geographic latitude of their formation, but also depending on their depth. Surface waters differ from deep and bottom waters. Deep and bottom waters are practically not affected by sunlight and heat. Their properties are more constant throughout the oceans, in contrast to surface pods, the properties of which 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 their health.
Instructions
The average salinity level of the World Ocean is 35 ppm - this is the figure most often cited in statistics. A slightly more accurate value, without rounding: 34.73 ppm. In practice, this means that in every liter of theoretical ocean water, about 35 g of salt should be dissolved. 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 homogeneous in terms of chemical properties.
The salinity of ocean water depends on several factors. Firstly, 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 the salinity increases. Therefore, in the tropics, in certain seasons, the salinity of water reaches record values for the planet. The largest part of the ocean is the Red Sea, its salinity is 43 ppm.
Moreover, 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 vibrations rarely exceed 6 ppm. In some areas, the salinity of the water decreases due to the abundance of fresh rivers flowing into the sea.
The salinity of the Pacific and Altantic 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 occurs especially intensively in the Southern Hemisphere. The currents of the Arctic Ocean also influence the Indian Ocean, which is why its salinity is lower than that of the Atlantic and Pacific Oceans.
The further from the poles, the higher the salinity of the ocean, for the same reasons. However, the saltiest latitudes are from 3 to 20 degrees in both directions from the equator, and not the equator itself. Sometimes these “stripes” are even said to be salinity belts. The reason for this distribution is that the equator is a zone of constant heavy tropical rainfall, which desalinizes the water.
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Not only the salinity changes, but also the temperature of the water in the World Ocean. Horizontally, the temperature changes from the equator to the poles, but there is also a vertical change in temperature: it decreases towards depth. The reason is that the sun is not able to penetrate the entire water column and heat the ocean waters to the very bottom. Water surface temperatures vary greatly. Near the equator it reaches +25-28 degrees Celsius, and near the North Pole it can drop to 0, and sometimes even a little lower.
Helpful advice
The area of the World Ocean is approximately 360 million square meters. km. This is about 71% of the entire planet's territory.
Water is the simplest chemical compound of hydrogen and oxygen, but ocean water is a universal, homogeneous ionized solution, which contains 75 chemical elements. These are solid minerals (salts), gases, as well as suspensions of organic and inorganic origin.
Vola has many different physical and chemical properties. First of all, they depend on the table of contents and the ambient temperature. Let's give a brief description of some of them.
Water is a solvent. Since water is a solvent, we can judge that all waters are gas-salt solutions of different chemical compositions and different concentrations.
Salinity of ocean, sea and river water
Salinity of sea water(Table 1). The concentration of substances dissolved in water is characterized by salinity, which is measured in ppm (%o), i.e. grams of a substance per 1 kg of water.
Table 1. Salt content in sea and river water (in% of the total mass of salts)
Basic connections |
Sea water |
river water |
Chlorides (NaCI, MgCb) |
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Sulfates (MgS0 4, CaS0 4, K 2 S0 4) |
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Carbonates (CaSOd) |
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Compounds of nitrogen, phosphorus, silicon, organic and other substances |
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Lines on a map connecting points with the same salinity are called isohalines.
Fresh water salinity(see Table 1) is on average 0.146%o, and sea - on average 35 %O. Salts dissolved in water give it a bitter-salty taste.
About 27 of the 35 grams is sodium chloride (table salt), so the water is salty. Magnesium salts give it a bitter taste.
Since the water in the oceans was formed from hot salty solutions of the earth's interior and gases, its salinity was original. There is reason to believe that in the first stages of the formation of the ocean, its waters differed little in salt composition from river waters. Differences emerged and began to intensify after the transformation of rocks as a result of their weathering, as well as the development of the biosphere. The modern salt composition of the ocean, as shown by fossil remains, developed no later than the Proterozoic.
In addition to chlorides, sulfites and carbonates, almost all chemical elements known on Earth, including noble metals, were found in sea water. However, the content of most elements in sea water is negligible; for example, only 0.008 mg of gold per cubic meter of water was detected, and the presence of tin and cobalt is indicated by their presence in the blood of marine animals and in bottom sediments.
Salinity of ocean waters— the value is not constant (Fig. 1). It depends on climate (the ratio of precipitation and evaporation from the ocean surface), the formation or melting of ice, sea currents, and near continents - on the influx of fresh river water.
Rice. 1. Dependence of water salinity on latitude
In the open ocean, salinity ranges from 32-38%; in the marginal and Mediterranean seas its fluctuations are much greater.
The salinity of waters down to a depth of 200 m is especially strongly influenced by the amount of precipitation and evaporation. Based on this, we can say that the salinity of sea water is subject to the law of zonation.
In equatorial and subequatorial regions, salinity is 34%c, because the amount of precipitation is greater than the water spent on evaporation. In tropical and subtropical latitudes - 37 since there is little precipitation and evaporation is high. In temperate latitudes - 35%o. The lowest salinity of sea water is observed in the subpolar and polar regions - only 32, since the amount of precipitation exceeds evaporation.
Sea currents, river runoff and icebergs disrupt the zonal pattern of salinity. For example, in the temperate latitudes of the Northern Hemisphere, water salinity is greater near the western shores of the continents, where currents bring saltier subtropical waters, and less salinity is near the eastern shores, where cold currents bring less salty water.
Seasonal changes in water salinity occur in subpolar latitudes: in the fall, due to the formation of ice and a decrease in the strength of river flow, the salinity increases, and in the spring and summer, due to the melting of ice and an increase in river flow, the salinity decreases. Around Greenland and Antarctica, salinity decreases during the summer as a result of the melting of nearby icebergs and glaciers.
The saltiest of all oceans is the Atlantic Ocean, the waters of the Arctic Ocean have the lowest salinity (especially off the Asian coast, near the mouths of Siberian rivers - less than 10%).
Among parts of the ocean - seas and bays - the maximum salinity is observed in areas limited by deserts, for example, in the Red Sea - 42%c, in the Persian Gulf - 39%c.
The salinity of water determines its density, electrical conductivity, ice formation and many other properties.
Gas composition of ocean water
In addition to various salts, various gases are dissolved in the waters of the World Ocean: nitrogen, oxygen, carbon dioxide, hydrogen sulfide, etc. As in the atmosphere, oxygen and nitrogen predominate in ocean waters, but in slightly different proportions (for example, the total amount of free oxygen in the ocean 7480 billion tons, which is 158 times less than in the atmosphere). Despite the fact that gases occupy relatively little space in water, this is enough to influence organic life and various biological processes.
The amount of gases is determined by the temperature and salinity of the water: the higher the temperature and salinity, the lower the solubility of gases and the lower their content in water.
So, for example, at 25 °C up to 4.9 cm/l of oxygen and 9.1 cm3/l of nitrogen can dissolve in water, at 5 °C - 7.1 and 12.7 cm3/l, respectively. Two important consequences follow from this: 1) the oxygen content in the surface waters of the ocean is much higher in temperate and especially polar latitudes than in low (subtropical and tropical) latitudes, which affects the development of organic life - the richness of the former and the relative poverty of the latter waters; 2) at the same latitudes, the oxygen content in ocean waters is higher in winter than in summer.
Daily changes in the gas composition of water associated with temperature fluctuations are small.
The presence of oxygen in ocean water promotes the development of organic life in it and the oxidation of organic and mineral products. The main source of oxygen in ocean water is phytoplankton, called the “lungs of the planet.” Oxygen is mainly spent on the respiration of plants and animals in the upper layers of sea waters and on the oxidation of various substances. In the depth range of 600-2000 m there is a layer oxygen minimum. A small amount of oxygen here is combined with a high content of carbon dioxide. The reason is the decomposition in this layer of water of the bulk of the organic matter coming from above and the intensive dissolution of biogenic carbonate. Both processes require free oxygen.
The amount of nitrogen in seawater is much less than in the atmosphere. This gas is mainly released into water from the air by the breakdown of organic matter, but is also produced by the respiration of marine organisms and their decomposition.
In the water column, in deep stagnant basins, as a result of the vital activity of organisms, hydrogen sulfide is formed, which is toxic and inhibits the biological productivity of waters.
Heat capacity of ocean waters
Water is one of the most heat-intensive bodies in nature. The heat capacity of just a ten meter layer of the ocean is four times greater than the heat capacity of the entire atmosphere, and a 1 cm layer of water absorbs 94% of the solar heat arriving at its surface (Fig. 2). Due to this circumstance, the ocean slowly warms up and slowly releases heat. Due to their high heat capacity, all water bodies are powerful heat accumulators. As the water cools, it gradually releases its heat into the atmosphere. Therefore, the World Ocean performs the function thermostat of our planet.
Rice. 2. Dependence of heat capacity on temperature
Ice and especially snow have the lowest thermal conductivity. As a result, ice protects the water on the surface of the reservoir from hypothermia, and snow protects the soil and winter crops from freezing.
Heat of vaporization water - 597 cal/g, and heat of fusion - 79.4 cal/g - these properties are very important for living organisms.
Ocean temperature
An indicator of the thermal state of the ocean is temperature.
Average ocean temperature- 4 °C.
Despite the fact that the surface layer of the ocean serves as the Earth's thermoregulator, in turn, the temperature of sea waters depends on the thermal balance (heat inflow and outflow). Heat inflow consists of , and heat consumption consists of the costs of water evaporation and turbulent heat exchange with the atmosphere. Despite the fact that the proportion of heat spent on turbulent heat exchange is not large, its significance is enormous. It is with its help that planetary heat redistribution occurs through the atmosphere.
At the surface, ocean temperatures range from -2°C (freezing point) to 29°C in the open ocean (35.6°C in the Persian Gulf). The average annual temperature of the surface waters of the World Ocean is 17.4°C, and in the Northern Hemisphere it is approximately 3°C higher than in the Southern Hemisphere. The highest temperature of surface ocean waters in the Northern Hemisphere is in August, and the lowest in February. In the Southern Hemisphere the opposite is true.
Since it has thermal relationships with the atmosphere, the temperature of surface waters, like the air temperature, depends on the latitude of the area, i.e., it is subject to the law of zonation (Table 2). Zoning is expressed in a gradual decrease in water temperature from the equator to the poles.
In tropical and temperate latitudes, water temperature mainly depends on sea currents. Thus, thanks to warm currents in tropical latitudes, temperatures in the western oceans are 5-7 °C higher than in the east. However, in the Northern Hemisphere, due to warm currents in the eastern oceans, temperatures are positive all year round, and in the west, due to cold currents, the water freezes in winter. In high latitudes, the temperature during the polar day is about 0 °C, and during the polar night under the ice - about -1.5 (-1.7) °C. Here the water temperature is mainly influenced by ice phenomena. In the fall, heat is released, softening the temperature of the air and water, and in the spring, heat is spent on melting.
Table 2. Average annual temperatures of ocean surface waters
Average annual temperature, "C |
Average annual temperature, °C |
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North hemisphere |
Southern Hemisphere |
North hemisphere |
Southern Hemisphere |
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The coldest of all oceans- Northern Arctic, and the warmest— The Pacific Ocean, since its main area is located in equatorial-tropical latitudes (average annual water surface temperature -19.1 ° C).
An important influence on the temperature of ocean water is exerted by the climate of the surrounding areas, as well as the time of year, since solar heat, which heats the upper layer of the World Ocean, depends on this. The highest water temperature in the Northern Hemisphere is observed in August, the lowest in February, and vice versa in the Southern Hemisphere. Daily fluctuations in sea water temperature at all latitudes are about 1 °C; the largest annual temperature fluctuations are observed in subtropical latitudes - 8-10 °C.
The temperature of ocean water also changes with depth. It decreases and already at a depth of 1000 m almost everywhere (on average) below 5.0 °C. At a depth of 2000 m, the water temperature levels out, decreasing to 2.0-3.0 ° C, and in polar latitudes - to tenths of a degree above zero, after which it either decreases very slowly or even increases slightly. For example, in the rift zones of the ocean, where at great depths there are powerful outlets of underground hot water under high pressure, with temperatures up to 250-300 ° C. In general, there are two main layers of water vertically in the World Ocean: warm superficial And powerful cold, extending to the bottom. Between them there is a transition temperature jump layer, or main thermal clip, within it there is a sharp drop in temperature.
This picture of the vertical distribution of water temperature in the ocean is disrupted at high latitudes, where at a depth of 300-800 m a layer of warmer and saltier water coming from temperate latitudes can be traced (Table 3).
Table 3. Average ocean water temperatures, °C
Depth, m |
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Equatorial |
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Tropical |
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Polar |
Change in water volume with temperature change
A sharp increase in the volume of water when freezing- This is a peculiar property of water. With a sharp drop in temperature and its transition through the zero mark, a sharp increase in the volume of ice occurs. As the volume increases, the ice becomes lighter and floats to the surface, becoming less dense. Ice protects deep layers of water from freezing, as it is a poor conductor of heat. The volume of ice increases by more than 10% compared to the initial volume of water. When heated, the opposite process of expansion occurs—compression.
Density of water
Temperature and salinity are the main factors determining the density of water.
For sea water, the lower the temperature and higher the salinity, the greater the density of the water (Fig. 3). Thus, at a salinity of 35%o and a temperature of 0 °C, the density of sea water is 1.02813 g/cm 3 (the mass of each cubic meter of such sea water is 28.13 kg more than the corresponding volume of distilled water). The temperature of sea water with the highest density is not +4 °C, like fresh water, but negative (-2.47 °C at a salinity of 30% and -3.52 °C at a salinity of 35%o
Rice. 3. Relationship between the density of sea ox and its salinity and temperature
Due to the increase in salinity, the density of water increases from the equator to the tropics, and as a result of a decrease in temperature, from temperate latitudes to the Arctic Circle. In winter, polar waters descend and move in the bottom layers towards the equator, so the deep waters of the World Ocean are generally cold, but enriched with oxygen.
The dependence of water density on pressure was revealed (Fig. 4).
Rice. 4. Dependence of seawater density (L"=35%o) on pressure at different temperatures
The ability of water to self-purify
This is an important property of water. During the process of evaporation, water passes through the soil, which, in turn, is a natural filter. However, if the pollution limit is violated, the self-cleaning process is disrupted.
Color and transparency depend on the reflection, absorption and scattering of sunlight, as well as on the presence of suspended particles of organic and mineral origin. In the open part, the color of the ocean is blue; near the coast, where there is a lot of suspended matter, it is greenish, yellow, and brown.
In the open part of the ocean, water transparency is higher than near the coast. In the Sargasso Sea, water transparency is up to 67 m. During the period of plankton development, transparency decreases.
In the seas such a phenomenon as glow of the sea (bioluminescence). Glow in sea water living organisms containing phosphorus, primarily such as protozoa (nightlight, etc.), bacteria, jellyfish, worms, fish. Presumably the glow serves to scare away predators, to search for food, or to attract individuals of the opposite sex in the dark. The glow helps fishing vessels locate schools of fish in seawater.
Sound conductivity - acoustic properties of water. Found in the oceans sound-diffusing my And underwater "sound channel" possessing sound superconductivity. The sound-dissipating layer rises at night and falls during the day. It is used by submariners to dampen noise from submarine engines, and by fishing vessels to detect schools of fish. "Sound
signal" is used for short-term forecast of tsunami waves, in underwater navigation for ultra-long-distance transmission of acoustic signals.
Electrical conductivity sea water is high, it is directly proportional to salinity and temperature.
Natural radioactivity sea waters are small. But many animals and plants have the ability to concentrate radioactive isotopes, so seafood catches are tested for radioactivity.
Mobility- a characteristic property of liquid water. Under the influence of gravity, under the influence of wind, attraction by the Moon and the Sun and other factors, water moves. As it moves, the water is mixed, which allows waters of different salinity, chemical composition and temperature to be evenly distributed.