The Pacific Ocean is the largest ocean on Earth. - Climatic zones of the Pacific Ocean
All natural belts are distinguished within the Pacific Ocean, except for the northern polar (arctic).
The northern subpolar (subarctic) belt occupies most of the seas. The northern subpolar belt has some peculiarities. It is not directly influenced by the waters of the Arctic basin, and powerful streams of warm, highly saline waters do not penetrate here. It is dominated by cold waters. There are extensive shelves within the belt. On the shallow shelf, biogenic substances are not irretrievably lost at great depths, but are included in the cycle of organic substances, therefore shelf waters are distinguished by high biological and commercial productivity.
The northern tropical belt stretches from the coast and Central America to and, continues to the coast and in the South China Sea. In a significant part of the belt, the trade winds of the Northern Hemisphere and the Northern Trade wind current dominate. Developed in the western part. The belt is characterized by high temperatures and salinity of waters, low bioproductivity.
The southern subtropical belt stretches in a winding strip of variable width from Southeast Australia and to the east, covering most of the region, an area between 30 and 40 ° S. sh., closer to the shores, descends to somewhat lower latitudes and approaches the coast between 20 and 35 ° S. sh. The deviation of the boundaries from the latitudinal strike is associated with the circulation of surface waters and the atmosphere. The axis of the belt in the open ocean is the subtropical convergence zone, where the waters of the South Tradewind Current and the northern stream of the circumpolar current converge. The position of the convergence zone is unstable, depends on the season and changes from year to year, however, the main processes typical for the belt are constant: the subsidence of air masses, the formation of an area of \u200b\u200bhigh pressure and marine tropical air, salinization of waters. On the eastern edge of the belt along the coast of Chile from south to north, there is a coastal one, where there is an intense drainage and rise of water, as a result of which a subtropical upwelling zone is formed and a large biomass is created.
The southern temperate belt includes most of the northern Antarctic Circumpolar Current. The northern boundary of the belt is close to 40-45 ° S. sh., and the southern one passes about 61-63 ° S. sh., i.e., along the northern border of the distribution of sea ice in September. The southern temperate belt is an area dominated by western, northwestern and southwestern, stormy, significant, low winter and summer surface waters and intensive transfer of surface waters to the east.
Physical geography of continents and oceans
OCEANS
PACIFIC OCEAN
Climate and hydrological conditions of the Pacific Ocean
Pacific Ocean extends between 60 ° north and south latitude. In the north, it is almost closed by the land of Eurasia and North America, separated from each other only by the shallow Bering Strait with the smallest width of 86 km, linking the Bering Sea of \u200b\u200bthe Pacific Ocean with the Chukchi Sea, which is part of the Arctic Ocean.
Eurasia and North America extend southward as far as the Northern Tropic in the form of vast, massive land areas, which are centers for the formation of continental air that can affect the climate and hydrological conditions of neighboring parts of the ocean. To the south of the Northern Tropic, the land becomes fragmented; up to the shores of Antarctica, its large land areas are only Australia in the southwest of the ocean and South America in the east, especially its extended part between the equator and 20 ° S latitude. South of 40 ° S The Pacific Ocean, together with the Indian and Atlantic, merge into a single water surface, not interrupted by large areas of land, over which the oceanic air of temperate latitudes is formed, and where Antarctic air masses freely penetrate.
The pacific ocean reaches greatest width (almost 20 thousand km) within the tropical-equatorial space, i.e. in that part where the solar thermal energy is supplied most intensively and regularly throughout the year. As a result, the Pacific Ocean receives more solar heat during the year than other parts of the World Ocean. And since the distribution of heat in the atmosphere and on the water surface depends not only on the direct distribution of solar radiation, but also on air exchange between land and water surface and water exchange between different parts of the World Ocean, it is quite clear that the thermal equator over the Pacific Ocean is displaced to the north. hemisphere and passes approximately between 5 and 10 ° N, and the northern part of the Pacific Ocean is generally warmer than the southern one.
Consider the main baric systemsdetermining meteorological conditions (wind activity, precipitation, air temperature), as well as the hydrological regime of surface waters (current systems, temperature of surface and subsurface waters, salinity) of the Pacific Ocean throughout the year. First of all, this is a near-equatorial depression (calm zone), somewhat widened towards the northern hemisphere. This is especially pronounced in the summer of the northern hemisphere, when an extensive and deep pressure depression is established over the strongly heated Eurasia, centered in the basin of the Indus River. In the direction of this depression, streams of humid unstable air rush from the subtropical centers of high pressure of both the northern and southern hemispheres. Most of the northern half of the Pacific Ocean at this time is occupied by the North Pacific maximum, along the southern and eastern periphery of which monsoons blow towards Eurasia. They are associated with heavy rainfall, the amount of which increases to the south. The second monsoon flow moves from the southern hemisphere, from the side of the pretropical high pressure belt. In the northwest, there is a weakened westerly transfer towards North America.
In the southern hemisphere, where it is winter at this time, strong westerly winds, carrying the air of temperate latitudes, cover the waters of all three oceans south of the parallel of 40 ° S. almost to the shores of Antarctica, where they are replaced by east and southeast winds blowing from the mainland. Western transport operates in these latitudes of the southern hemisphere in the summer, but with less force. Winter conditions in these latitudes are characterized by abundant rainfall, stormy winds, and high waves. With a large number of icebergs and floating sea ice, travel in this part of the World Ocean is fraught with great dangers. It is not for nothing that seafarers have long called these latitudes "the roaring forties."
At the corresponding latitudes in the northern hemisphere, the prevailing atmospheric process is also the western transport, but due to the fact that this part of the Pacific Ocean from the north, west and east is closed by land, in winter there is a somewhat different meteorological situation than in the southern hemisphere. Cold and dry continental air from Eurasia enters the ocean with the western transport. It is involved in the closed system of the Aleutian minimum, which forms over the North Pacific Ocean, transforms and is carried to the shores of North America by southwestern winds, leaving abundant rainfall in the coastal zone and on the slopes of the Cordilleras of Alaska and Canada.
Wind systems, water exchange, features of the ocean floor topography, the position of continents and the outlines of their shores affect the formation of surface ocean currents, and these, in turn, determine many features of the hydrological regime. In the Pacific Ocean, with its vast dimensions within the intertropical space, there is a powerful system of currents generated by the trade winds of the northern and southern hemispheres. In accordance with the direction of movement of the trade winds along the equatorial margins of the North Pacific and South Pacific maximums of the current, these move from east to west, reaching a width of more than 2000 km. The North Passat Current flows from the coast of Central America to the Philippine Islands, where it splits into two branches. The southern part spreads over the inter-island seas and partly feeds the surface inter-trade countercurrent flowing along the equator and north of it, advancing towards the Central American isthmus. The northern, more powerful branch of the North Passat Current goes to the island of Taiwan, and then enters the East China Sea, skirting the Japanese islands from the east, gives rise to a powerful system of warm currents in the North Pacific Ocean: this is the Kuroshio Current, or the Japanese current, moving at a speed from 25 to 80 cm / s. Near the island of Kyushu, the Kuroshio forks, and one of the branches enters the Sea of \u200b\u200bJapan under the name of the Tsushima Current, the other goes into the ocean and follows along the eastern shores of Japan, while at 40 ° N. it is not pushed to the east by the cold Kuril-Kamchatka countercurrent or Oyashio. The continuation of the Kuroshio to the east is called the Kuroshio Drift, and then the North Pacific Current, which heads towards the shores of North America at a speed of 25-50 cm / s. In the eastern part of the Pacific Ocean north of the 40th parallel, the North Pacific Current forks into the warm Alaskan Current, heading towards the shores of South Alaska, and the cold California Current. The latter, following along the coast of the mainland, to the south of the tropic flows into the North Tradewind Current, closing the northern circulation of the Pacific Ocean.
Most of the Pacific Ocean north of the equator is dominated by high surface water temperatures. This is facilitated by the large width of the ocean in the intertropical space, as well as by the system of currents that carry the warm waters of the North Passat Current to the north along the shores of Eurasia and neighboring islands.
North trade wind the whole year carries water with a temperature of 25 ... 29 ° С. The high temperature of surface waters (approximately to a depth of 700 m) persists within the Kuroshio to almost 40 ° N. (27 ... 28 ° С in August and up to 20 ° С in February), as well as within the North Pacific Current (18 ... 23 ° С in August and 7 ... 16 ° С in February). A significant cooling effect on the northeast of Eurasia up to the north of the Japanese Islands is exerted by the cold Kamchatka-Kuril Current originating in the Bering Sea, which is intensified in winter by cold waters coming from the Sea of \u200b\u200bOkhotsk. From year to year, its capacity varies greatly depending on the severity of winters in the Bering and Okhotsk Seas. The region of the Kuril Islands and Hokkaido Islands is one of the few in the North Pacific Ocean where ice is present in winter. At 40 ° N lat. when it meets the Kuroshio Current, the Kuril Current plunges to a depth and flows into the North Pacific. In general, the water temperature in the North Pacific is higher than in the South at the same latitudes (5 ... 8 ° C in August in the Bering Strait). This is partly due to the limited water exchange with the Arctic Ocean due to the threshold in the Bering Strait.
South Tradewind Current moves along the equator from the coast of South America to the west and even enters the northern hemisphere up to about 5 ° N. In the area of \u200b\u200bthe Moluccas, it branches: the bulk of the water, together with the North Trade Wind, enters the Inter-trade Countercurrent system, and the other branch enters the Coral Sea and, moving along the coast of Australia, forms the warm East Australian Current, which flows off the coast of the Tasmania island during Western winds. The surface water temperature in the South Passat Current is 22 ... 28 ° С, in the East Australian in winter from north to south it varies from 20 to 11 ° С, in summer - from 26 to 15 ° С.
Circumpolar Antarctic, or the current of the Western winds, enters the Pacific Ocean south of Australia and New Zealand and moves in a sublatitudinal direction to the shores of South America, where its main branch deviates to the north and, passing along the coasts of Chile and Peru under the name of the Peruvian Current, turns westward, merging into the South Passat , and closes the Cycle of the southern half of the Pacific Ocean. The Peruvian current carries relatively cold waters and reduces the air temperature over the ocean and off the western coasts of South America almost to the equator to 15 ... 20 ° С.
In distribution salinity surface waters in the Pacific Ocean, there are certain patterns. With an average ocean salinity of 34.5-34.6% o, the maximum values \u200b\u200b(35.5 and 36.5% s) are observed in the zones of intense trade wind circulation in the northern and southern hemispheres (between 20 and 30 ° N and 10 and 20 ° S) This is associated with a decrease in precipitation and an increase in evaporation compared to the equatorial regions. Up to the forties latitudes of both hemispheres in the open part of the ocean, salinity is 34-35% o. The lowest salinity is in high latitudes and in the coastal regions of the northern part of the ocean (32-33% o). There, this is due to the melting of sea ice and icebergs and the desalinating effect of river runoff, therefore, there are significant seasonal fluctuations in salinity.
The size and configuration of the greatest of the Earth's oceans, the peculiarities of its connections with other parts of the World Ocean, as well as the size and configuration of the surrounding land areas and the associated directions of circulation processes in the atmosphere created a number of features Pacific Ocean: the average annual and seasonal temperatures of its surface waters are higher than in other oceans; the portion of the ocean in the northern hemisphere is generally much warmer than the southern, but in both hemispheres the western half is warmer and receives more rainfall than the eastern.
The Pacific Ocean, more than other parts of the World Ocean, is the scene of the birth of the atmospheric process known as tropical cyclones or hurricanes... These are vortices of small diameter (no more than 300-400 km) and high speed (30-50 km / h). They form within the tropical convergence zone of the trade winds, usually during the summer and autumn of the northern hemisphere, and move first in accordance with the direction of the prevailing winds, from west to east, and then along the continents to the north and south. For the formation and development of hurricanes, a vast body of water, heated from the surface to at least 26 ° C, and atmospheric energy are required, which would impart a forward motion to the formed atmospheric cyclone. The features of the Pacific Ocean (its dimensions, in particular, the width within the intertropical space, and the maximum surface water temperatures for the World Ocean) create conditions over its water area that contribute to the emergence and development of tropical cyclones.
The passage of tropical cyclones is accompanied by catastrophic events: winds of destructive force, strong waves in the open sea, heavy rainfall, flooding of plains on the adjacent land, floods and destruction, leading to severe disasters and loss of life. Moving along the coasts of the continents, the most powerful hurricanes go beyond the boundaries of the intertropical space, transforming into extra-tropical cyclones, sometimes reaching great strength.
The main origin of tropical cyclones in the Pacific Ocean is located south of the Tropic, east of the Philippine Islands. Moving initially to the west and northwest, they reach the shores of Southeast China (in Asian countries, these eddies are called typhoon in China) and move along the continent, deviating towards the Japanese and Kuril Islands.
Branches of these hurricanes, deviating to the west south of the tropic, penetrate the inter-island seas of the Sunda Archipelago, into the northern part of the Indian Ocean and cause destruction in the lowlands of Indochina and Bengal. Hurricanes originating in the southern hemisphere north of the Tropic are moving towards the shores of Northwest Australia. There they bear the local name "BILLY-BILLY". Another center for the origin of tropical hurricanes in the Pacific Ocean is located off the western shores of Central America, between the Tropic and the Equator. From there, hurricanes rush to the coastal islands and shores of California.
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In the Pacific Ocean, all climatic zones are distinguished with the exception of the north polar (arctic). The western and eastern Pacific oceans differ significantly from each other and from the central regions of the ocean. As a result, within the belts, as a rule, physical and geographical regions are distinguished. In each specific area, natural conditions and processes are determined by the position in relation to the continents and islands, the depth of the ocean, the peculiarity of air and water circulation, etc. In the western part of the Pacific Ocean, marginal and inter-island seas are usually isolated as physical and geographical regions, in the eastern - areas of intense upwelling.
Northern subpolar (subarctic) belt
Unlike the Atlantic Ocean, the Pacific part of the belt is quite isolated from the influence of the Arctic Ocean. The belt occupies most of the Bering and Okhotsk seas.
In autumn and winter, the surface water cools to the freezing point and large masses of ice form. Cooling is accompanied by salinization of water. In summer, sea ice gradually disappears, the temperature of the thin upper layer rises to 3-5 ° С, in the south - up to 10 ° С. Below, cold water remains, forming an intermediate layer formed as a result of winter cooling. Thermohaline convection, summer heating and desalination of water (30-33% o) as a result of ice melting, the interaction of streams of warm currents (Aleutian) with cold subpolar waters determine a relatively high content of nutrients in surface waters and a high bioproductivity of the subarctic belt. Nutrients are not lost at great depths, since there are vast shelves within the water area. In the subarctic belt, two regions are distinguished: the Bering and Okhotsk seas, rich in valuable commercial fish, invertebrates and sea animals.
Northern temperate belt
In the Pacific Ocean, it covers vast areas from Asia to North America and occupies an intermediate position between the main areas of formation of cold subarctic and warm subtropical and tropical waters.
In the west of the belt, the warm Kuroshio current and the cold Kuril current (Oyashio) interact. From the mixed water flows, the North Pacific Current is formed, which occupies a significant part of the water area and transports huge masses of water and heat from west to east under the influence of the prevailing westerly winds. The temperature of the water throughout the year in the temperate zone varies greatly. In winter, near the coast, it can drop to 0 ° С, in summer it rises to 15-20 ° С (in the Yellow Sea up to 28 ° С). Ice forms only in limited inland areas of shallow seas (for example, in the northern part of the Sea of \u200b\u200bJapan). In winter, vertical thermal convection of water develops with the participation of intense wind mixing: cyclonic activity is active in temperate latitudes. The high content of oxygen and nutrients in the water provides a relatively high bioproductivity, and its value in the northern part of the belt (subpolar waters) is higher than in the southern part (subtropical waters). The salinity of waters in the northern half of the water area is 33% o, in the southern half it is close to the average - 35% o. The western part of the belt is characterized by monsoon circulation, sometimes typhoons come here. Within the belt, the regions of the Japanese and Yellow Seas and the Gulf of Alaska are distinguished.
Northern subtropical belt
It is located between the zone of westerly winds of temperate latitudes and trade winds of equatorial-tropical latitudes. The middle part of the water area is surrounded by the northern subtropical ring of currents.
Due to the prevailing air subsidence and its stable stratification within the belt, there is usually a clear sky, low precipitation and relatively dry air. There are no prevailing air currents, the winds are weak and changeable, calm is characteristic. Evaporation is very high due to dry air and high
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Circulation of the Pacific Ocean atmosphere.
The main features of the atmospheric circulation over the Pacific Ocean are determined by five areas of high and low pressure, and in accordance with the location of the baric centers, the direction of the winds of the Pacific Ocean is formed:
- In subtropical latitudes of both hemispheres over the Pacific Ocean, two dynamic regions of high pressure are constant - the North Pacific, or Hawaiian, and South Pacific highs, the centers of which are located in the eastern part of the ocean. Subtropical highs determine the existence of a stable system of trade winds in the tropical and subtropical latitudes of the Pacific Ocean, consisting of the northeast trade wind in the Northern Hemisphere and the southeast in the South.
- In equatorial latitudes these areas are separated by a permanent dynamic reduced pressure area, developed more strongly in the west. The trade wind zones are separated by the equatorial calm belt, in which weak and unstable winds prevail with a high frequency of calm.
- North and South of Subtropical Highs at higher latitudes, there are two minima - the Aleutian minima centered over the Aleutian Islands and the Antarctic minima stretching from east to west in the Antarctic zone. The first exists only in winter in the Northern Hemisphere, the second - throughout the year.
The climate and relief of the surrounding continents have a significant impact on the circulation of the atmosphere over the Pacific Ocean. For example,
- Cordillera prevent oceanic air currents from penetrating deep into the American continents, contribute to the stationing (stopping) of subtropical anticyclones near the eastern shores of the ocean.
- The climate of the Northwest Pacific is influenced by seasonal changes in atmospheric pressure over Asia and the seasonal monsoon circulation caused by it.
- In the tropics, islands have a significant effect on atmospheric circulation Indonesian archipelago... The complex orography of these islands under the conditions of monsoon winds contributes to the development of convection, the formation of clouds, and significant precipitation. Condensation releases a lot of heat, resulting in a permanent pressure depression.
Pacific winds.
Fig 1. General circulation of the atmosphere.
For the Pacific Northwest the monsoon circulation of the atmosphere is characteristic. In winter, dominates here northwest monsoon bringing cold and dry air from the Asian mainland, in summer - southeast monsoon carrying warm and humid air from the ocean. Monsoons disrupt the trade wind circulation and lead to air overflow from the Northern Hemisphere to the Southern Hemisphere in winter and in the opposite direction in summer.
In the temperate latitudes of the northern hemisphere in winter prevail strong westerly winds , and in the summer - weak southern. The frequency of storms in the northern temperate latitudes of the Pacific Ocean is 30% in winter and 5% in summer. The recurrence of storm winds is due to the occurrence of a large number of cyclones at polar fronts (at the meeting point of tropical and polar air masses).
In the subtropics and tropics of the northern hemisphere dominate northeast trade winds ... In tropical latitudes, constant winds reach the strength of a storm extremely rarely, but at times tropical hurricanes - typhoons pass here. In the Northern Hemisphere, typhoons travel mainly from the area to the east and northwest of the Philippines to Japan. Typhoons most often occur in the warm half of the year in the western part of the Pacific Ocean, in the eastern part of the ocean typhoons are rare and occur only in the Northern Hemisphere.
In the equatorial zone all year round is observed mainly calm weather .
In the tropical and subtropical zones of the southern hemisphere a stable southeast trade wind strong in winter and weak in summer. In the tropics of the Southern Hemisphere, typhoons originate in the area of \u200b\u200bthe New Hebrides and Samoa and move towards Australia.
In the southern temperate latitudes observed strong persistent westerly winds ... The recurrence of storms here is 25-35%.
In the high latitudes of the southern hemisphere the winds are subject to the general cyclonic circulation characteristic of the low-pressure Antarctic region. In the northern part of Antarctica, westerly winds prevail, often of hurricane strength - up to 75 m / s (the so-called "violent fifties"). Near the mainland dominate east winds , which, merging with the katabatic winds of predominantly southeastern directions, form an air flow along the coast from east to west.
Sailors from latitudes 40 to 70 degrees south, from the era of sailing ships, are known as the Roaring Forties, Furious Fifties, and Piercing Sixties due to bad weather, stormy winds and large waves generated by the movement of air masses , which, flowing around the globe, do not encounter obstacles in the form of any noticeable land masses.
Since ancient times, it has occupied an important place in European culture. Actually, it got its name from the light hand of Herodotus, who used in his works the myth of Atlanta, holding the sky to the west of Greece on his shoulders. But at the level of development of Greek science at that time, it was impossible to reliably know in which climatic zones the Atlantic Ocean is located.
From the Arctic to Antarctica
All the huge variety of climatic zones and the biological wealth of the ocean is due to the fact that it has a huge length along the meridian from north to south. The extreme northern point of the ocean is in the subarctic belt, and the southern one reaches the shores of Antarctica.
You can definitely say in which climatic zones the Atlantic Ocean is located: it is subarctic, temperate, subtropical, tropical and subequatorial.
It should be noted that the only belt not represented in the ocean is the equatorial one. This is due to the fact that the main qualities of this belt can manifest themselves only on land.
Atlantic Ocean. General information, climate
All well-known historical seas such as the Mediterranean, Baltic and Black with all their bays and straits belong to the Atlantic Ocean system.
The generally accepted designation for the northern boundary of the ocean runs along the entrance to Hudson Bay and the southern coast of Greenland all the way to Scandinavia. The demarcation line with the Indian is an imaginary straight line stretching from Cape Agulhas to the coast of Antarctica. The Atlantic Ocean is separated from the Pacific Ocean by the sixty-eighth meridian.
However, it is not only the vast extent of the ocean from south to north that affects the climate above its surface. Underwater currents and movements of air currents are also important. This means that it is important not only in which climatic zones the Atlantic Ocean is located, but also what the weather is in neighboring regions.
Above the surface of the ocean and its coast, there is a pronounced seasonal variability of the weather - in the summer, there are strong tropical hurricanes and heavy rains. Forming off the west coast, violent hurricanes move westward, reaching the coasts of Western Europe in the region of Portugal and Ireland.
In addition, the exchange of water masses with the Arctic and Southern Oceans has a strong impact on weather fluctuations.
Characteristics of the Atlantic Ocean. Bottom geography
Let's consider this important issue as well. The climatic zones in which the Atlantic Ocean is located affects the structure of the ocean floor, especially its coastal part, which is rich in relic sediments associated with the confluence of rivers, which brought biological remains and other organic matter from the mainland. Later, when the water level in the Atlantic changed, the channels of these rivers were flooded and this had a decisive impact on the formation of the shelf of the European continent.
The richness of the southern coastal ocean waters contributes to the formation of a large number of coral reefs.
Ecology and pollution
Regardless of what climatic zones the Atlantic Ocean is located in, human activities sometimes have a devastating effect on it. In recent decades, aquatic ecosystems have been severely tested due to more intensive shipping, flooding of hazardous waste and frequent oil spills.
