Many people know about the Gulf Stream, which, carrying huge masses of water from equatorial latitudes to polar latitudes, literally warms the north Western Europe and Scandinavia. But few people know that there are other warm and cold currents of the Atlantic Ocean. How do they affect coastal climate? Our article will tell about this. In fact, there are a lot of currents in the Atlantic. Let us list them briefly for general development. These are West Greenlandic, Angolan, Antillean, Bengueland, Guinean, Lomonosov, Brazilian, Guiana, Azores, Gulf Stream, Irminger, Canary, East Icelandic, Labrador, Portuguese, North Atlantic, Florida, Falkland, North equatorial ... Not all of them have an impact on the climate. big influence... Some of them are generally part or fragments of the main, larger currents. Here we will talk about them in our article.
Why currents form
The world's oceans are constantly circulating large invisible "rivers without banks". In general, water is a very dynamic element. But with the rivers everything is clear: they flow from source to mouth because of the difference in heights between these points. But what makes huge bodies of water move within the ocean? Of the many reasons, two are the main ones: trade winds and changes in atmospheric pressure. Because of this, currents are divided into drift and baro-gradient. The first are formed by trade winds - winds constantly blowing in one direction. The majority of such currents. The mighty rivers carry a large amount of water into the seas, different from the sea in density and temperature. Such currents are called sink, gravitational and frictional. Consideration should also be given to the great north-south extent of the Atlantic Ocean. The currents in this area, therefore, are more meridional than latitudinal.
What are trade winds
Winds are the main reason for the movement of huge masses of water in the oceans. But what are trade winds? The answer lies in the equatorial regions. The air warms up there more than in other latitudes. It rises up and over upper layers the troposphere spreads out towards the two poles. But already at a latitude of 30 degrees, having thoroughly cooled down, it sinks down. Thus, a circulation of air masses is created. In the equator, a zone of low pressure appears, and in tropical latitudes - high. And here the rotation of the Earth around the axis manifests itself. If not for it, the trade winds would blow from the tropics of both hemispheres to the equator. But, as our planet rotates, the winds are deflected, acquiring a westerly direction. This is how the trade winds shape the main currents of the Atlantic Ocean. They move clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere. This is because in the first case the trade winds blow from the northeast, and in the second - from the southeast.
Impact on climate
Based on the fact that the main currents originate in the equatorial and tropical regions, it would be reasonable to assume that they are all warm. But this does not always happen. The warm current in the Atlantic Ocean, having reached the polar latitudes, does not fade away, but, having made a smooth circle, reverses, but has already cooled down considerably. This can be seen in the example of the Gulf Stream. It carries warm masses of water from the Sargasso Sea to northern Europe. Then, under the influence of the Earth's rotation, it deviates to the west. Under the name of the Labrador Current, it descends along the coast of the North American continent to the south, cooling the coastal regions of Canada. It should be said that these masses of water are called warm and cold conditionally - relative to temperature environment... For example, in the North Cape Current in winter the temperature is only +2 ° С, and in summer it is maximum +8 ° С. But it is called warm because the water in the Barents Sea is even colder.
Major Atlantic currents in the Northern Hemisphere
Here, of course, one cannot fail to mention the Gulf Stream. But also others passing through Atlantic Ocean currents have an important effect on the climate of nearby territories. A north-east trade wind is born at Cape Verde (Africa). He drives huge warmed up masses of water to the west. Crossing the Atlantic Ocean, they connect with the Antilles and Guiana currents. This intensified jet is moving towards The Caribbean... After that, the waters rush north. This continuous clockwise movement is called the Warm North Atlantic Current. Its edge at high latitudes is vague and blurred, and at the equator it is more distinct.
Mysterious "Stream from the Gulf" (Golf-Stream)
This is the name of the current in the Atlantic Ocean, without which Scandinavia and Iceland would turn, based on their proximity to the pole, into the land of eternal snows. It used to be thought that the Gulf Stream was born in the Gulf of Mexico. Hence the name. In fact, only a small part of the Gulf Stream flows out of the Gulf of Mexico. The main stream comes from the Sargasso Sea. What is the mystery of the Gulf Stream? The fact that, contrary to the rotation of the Earth, it flows not from west to east, but into reverse direction... Its capacity exceeds the discharge of all the rivers of the planet. The speed of the Gulf Stream is impressive - two and a half meters per second on the surface. The current can also be traced at a depth of 800 meters. And the stream width is 110-120 kilometers. Due to the high speed of the current, the water from the equatorial latitudes does not have time to cool down. The surface layer has a temperature of +25 degrees, which, of course, plays a primary role in the formation of the climate of Western Europe. The mystery of the Gulf Stream also lies in the fact that it does not wash the continents anywhere. Between it and the coast there is always a strip of colder water.
Atlantic Ocean: Currents of the Southern Hemisphere
From African continent the American trade wind drives a jet, which, due to low pressure in the equatorial region, begins to deviate to the south. This is how a cycle similar to the northern one begins. However, the South Tradewind Current moves counterclockwise. It also runs across the Atlantic Ocean. Currents Guiana, Brazilian (warm), Falkland, Benguela (cold) are part of this cycle.
The oceans are an incredibly complex multifaceted system that has not been fully studied to date. Water in large bodies of water should not be stationary, as this would quickly lead to large-scale environmental disaster... One of critical factors maintaining the balance on the planet are the currents of the oceans.
Reasons for the formation of currents
The ocean current is a periodic or, on the contrary, a constant movement of impressive volumes of water. Very often currents are compared with rivers that exist according to their own laws. The circulation of water, its temperature, power and flow rate - all these factors are due to external influences.
The main characteristics of the ocean current are direction and speed.
The circulation of water flows in the oceans occurs under the influence of physical and chemical factors. These include:
- Wind... Under the influence of strong air currents, water moves on the surface of the ocean and at its shallow depth. The wind has no effect on deep currents.
- Space... Influence space bodies(Sun, Moon), as well as the rotation of the Earth in orbit and around its axis leads to the displacement of water layers in the World Ocean.
- Different indicators of water density- that on which the appearance of ocean currents depends.
Rice. 1. The formation of currents largely depends on the influence of space.
Direction of currents
Depending on the direction of water flows, they are divided into 2 types:
- Zonal- moving to the East or West.
- Meridian- directed to the North or South.
There are other types of currents, the appearance of which is caused by the ebb and flow. They are called tidal, and they have the greatest power in the coastal zone.
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Sustainable are called currents in which the strength of the flow and its direction remain unchanged. These include the South trade wind and North trade wind currents.
If the stream is modified, then it is called unstable... This group includes all surface currents.
Our ancestors knew about the existence of currents from time immemorial. During shipwrecks, sailors threw corked bottles into the water with notes with the coordinates of the incident, requests for help or words of farewell. They firmly knew that sooner or later their messages would get to people precisely because of the currents.
Warm and cold currents of the World Ocean
The formation and maintenance of the climate on the globe is greatly influenced by ocean currents, which, depending on the temperature of the water, are warm and cold.
Water streams are called warm if the temperature is above 0. These include the Gulf Stream, Kuroshio, Alaska and others. They usually move from low to high latitudes.
The warmest current in the oceans is El Niño, whose name is translated from Spanish as the Child of Christ. And this is not without reason, since a strong and full of surprises current appears on the globe on Christmas Eve.
Fig. 2. El Niño is the warmest current.
Cold currents have a different direction of movement, the largest of which are Peruvian and California.
The division of ocean currents into cold and warm ones is rather arbitrary, since it shows the ratio of the temperature of the water in the stream to the temperature of the surrounding water. For example, if the water in the thickness of the current is warmer than in the surrounding water space, then such a flow is called heat, and vice versa .. Total estimates are: 326.
As a rule, their movement occurs in a strictly defined direction and can have a large extent. The current map below displays them in full.
Water streams are of considerable size: they can be tens, or even hundreds of kilometers wide, and have a great depth (hundreds of meters). The speed of oceanic and sea currents is different - on average, it is 1-3 thousand m / hour. But, there are also so-called high-speed ones. Their speed can reach 9,000 m / h.
Where do currents come from?
The causes of water currents can be a sharp change in water temperature due to heating, or, conversely, cooling. They are also influenced by different densities, for example, in a place where several streams (marine and oceanic) collide, precipitation, evaporation. But mainly cold and warm currents arise due to the action of winds. Therefore, the direction of the largest oceanic water flows depends mainly on the air currents of the planet.
Wind-driven currents
Trade winds are an example of constantly blowing winds. They start their lives from the 30's latitudes. The currents created by these air masses are called trade wind currents. There are South Passat and North Passat currents. In the temperate zone, such water flows are formed under the influence of westerly winds. They form one of the largest currents on the planet. In the northern and southern hemispheres, there are two cycles of the water flow: cyclonic and anticyclonic. Their formation is influenced by the inertial force of the Earth.
Varieties of currents
Mixed, neutral, cold and warm currents are types of circulating masses on the planet. When the temperature of the stream water is lower than the temperature of the surrounding water, it is If, on the contrary, it is its warm variety. The neutral currents do not differ from the temperature of the surrounding waters. And mixed ones can change along the entire length. It should be noted that there is no constant temperature indicator of currents. This figure is very relative. It is determined by comparing the surrounding water masses.
In tropical latitudes, warm currents circulate along the eastern outskirts of the continents. Cold ones - along the western ones. In temperate latitudes, warm currents pass along the western shores, and cold currents along the east. You can also determine the variety by another factor. So, there is an easier rule: cold currents go to the equator, and warm ones - from it.
Meaning
It is worth talking about in more detail. The cold and warm current plays important role On the Earth. The significance of the circulating water masses is that, due to their movement, the solar heat is redistributed on the planet. Warm currents increase the air temperature in nearby areas, while cold currents lower it. Formed on water, water currents have a serious impact on the mainland. In areas where warm currents constantly pass, the climate is humid, where cold ones, on the contrary, dry. Also, ocean currents contribute to the migration of fish fauna of the oceans. Under their influence, plankton moves, and fish migrate behind it.
Examples of warm and cold currents can be cited. Let's start with the first variety. The largest are the following water streams: Gulf Stream, Norwegian, North Atlantic, North and South Passat, Brazilian, Kuroshio, Madagascar and others. The coldest ocean currents: Somali, Labrador, California.
Major currents
The largest warmest current on the planet is the Gulf Stream. This is a meridional circulating stream, carrying 75 million tons of water every second. The width of the Gulf Stream is from 70 to 90 km. Thanks to him, Europe gets a comfortable mild climate. It follows from this that the cold and warm current largely affects the life of all living organisms on the planet.
Of the zonal, cold streams, the current is of the greatest importance. In the southern hemisphere, not far from the shores of Antarctica, there are no island or continental accumulations. A large area of the planet is completely filled with water. Here, the Indian, Quiet converge into one stream and unite into a separate huge reservoir. Some scientists acknowledge its existence and call it Southern. It is here that the largest flow of water is formed - the current of the Western winds. Every second it carries a stream of water that is three times the size of the Gulf Stream.
Canary or cold?
Currents can change their temperature. For example, the flow begins with cold masses. Then it warms up and becomes warm. One of the variants of such a circulating water mass is the Canary Current. It originates in the northeast of the Atlantic Ocean. Sent by a cold stream along Europe. Passing along the west coast of Africa, it gets warm. This current has long been used by sailors to travel.
Mariners learned about the presence of ocean currents almost immediately, as soon as they began to surf the waters of the World Ocean. True, the public paid attention to them only when, thanks to the movement of ocean waters, many great geographical discoveries for example, Christopher Columbus sailed to America thanks to the North Equatorial Current. After that, not only sailors, but also scientists began to pay close attention to ocean currents and strive to investigate them as best and deeply as possible.
Already in the second half of the XVIII century. sailors studied the Gulf Stream quite well and successfully applied the knowledge gained in practice: from America to Great Britain they went with the flow, and in the opposite direction they kept a certain distance. This allowed them to be two weeks ahead of ships whose captains were not familiar with the terrain.
Oceanic or sea currents are called large-scale movements of the water masses of the World Ocean at a speed of 1 to 9 km / h. These streams do not move chaotically, but in a certain channel and direction, which is the main reason why they are sometimes called rivers of the oceans: the width of the largest currents can be several hundred kilometers, and the length can reach more than one thousand.
It was found that water flows do not move straight, but deviate slightly to the side, obeying the Coriolis force. In the Northern Hemisphere, they almost always move clockwise, in the Southern Hemisphere, vice versa.... At the same time, currents in tropical latitudes (they are called equatorial or trade winds) move mainly from east to west. The strongest currents have been recorded along the eastern coasts of the continents.
Water flows do not circulate by themselves, but they are set in motion by a sufficient number of factors - wind, rotation of the planet around its axis, gravitational fields of the Earth and the Moon, bottom topography, outlines of continents and islands, the difference in temperature indicators of water, its density, depth in different places of the ocean and even its physical and chemical composition.
Of all the types of water flows, the most pronounced are the surface currents of the World Ocean, the depth of which is often several hundred meters. Their occurrence was influenced by trade winds, constantly moving in tropical latitudes in a west-east direction. These trade winds form huge streams of the North and South Equatorial currents near the equator. A smaller part of these flows returns to the east, forming a countercurrent (when the movement of water occurs in the direction opposite to the movement of air masses). Most, colliding with continents and islands, turn to the north or south.
Warm and cold streams of water
It should be borne in mind that the concepts of "cold" or "warm" currents are conditional definitions. So, despite the fact that the temperature indicators of the water flows of the Benguela Current, which flows along the Cape of Good Hope, are 20 ° C, it is considered cold. But the North Cape Current, which is one of the branches of the Gulf Stream, with temperatures ranging from 4 to 6 ° C, is warm.
This happens because cold, warm and neutral currents got their names based on comparing the temperature of their water with the temperature indicators of the ocean surrounding them:
- If the temperature indicators of the water flow coincide with the temperature of the surrounding waters, such a flow is called neutral;
- If the temperature of the currents is lower than the surrounding water, they are called cold. They usually flow from high latitudes to low latitudes (for example, the Labrador Current), or from areas where ocean water has a low salinity due to large river flows. surface waters;
- If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from tropical to circumpolar latitudes, such as the Gulf Stream.
Major water streams
On the this moment scientists have recorded about fifteen major oceanic water flows in the Pacific, fourteen in the Atlantic, seven in the Indian and four in the Arctic Ocean.
It is interesting that all currents of the Arctic Ocean move at the same speed - 50 cm / sec, three of them, namely West Greenland, West Spitsbergen and Norwegian, are warm, and only East Greenland belongs to the cold current.
But almost all the oceanic currents of the Indian Ocean are warm or neutral, while the Monsoon, Somali, Western Australian and the Cape Needle Current (cold) move at a speed of 70 cm / sec., The speed of the rest varies from 25 to 75 cm / sec. The water flows of this ocean are interesting in that, together with the seasonal monsoon winds, which change their direction twice a year, the oceanic rivers also change their course: in winter they mainly flow to the west, in summer - to the east (a phenomenon characteristic only for the Indian Ocean ).
Since the Atlantic Ocean stretches from north to south, its currents also have a meridional direction. Water streams located in the north move clockwise, in the south - against it.
A striking example of the current of the Atlantic Ocean is the Gulf Stream, which, starting in the Caribbean Sea, carries warm waters to the north, splitting along the road into several side streams. When the waters of the Gulf Stream find themselves in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of the cold Greenland Current, after which at some stage they deviate to the west and again adjoin the Gulf Stream, forming a vicious circle.
The currents of the Pacific Ocean are mainly latitudinal and form two huge circles: north and south. Since the Pacific Ocean is extremely large, it is not surprising that its water currents have a significant impact on most our planet.
For example, trade wind streams distill warm waters from the western tropical shores to the eastern ones, which is why in the tropical zone Western part The Pacific Ocean is much warmer than the opposite side. But in the temperate latitudes of the Pacific Ocean, on the contrary, the temperature is higher in the east.
Deep currents
For quite a long time, scientists believed that deep ocean waters were almost motionless. But soon special underwater vehicles discovered both slow and fast-flowing water currents at great depths.
For example, under Equatorial current In the Pacific Ocean at a depth of about one hundred meters, scientists have identified the underwater stream Cromwell, moving eastward at a speed of 112 km / day.
A similar movement of water flows, but already in the Atlantic Ocean, was found by Soviet scientists: the width of the Lomonosov current is about 322 km, and the maximum speed of 90 km / day was recorded at a depth of about one hundred meters. After that, another underwater stream was discovered in Indian Ocean, however, its speed was much lower - about 45 km / day.
The discovery of these currents in the ocean gave rise to new theories and mysteries, the main one of which is the question - why they appeared, how they formed, and also whether the entire ocean area is covered by currents or is there a point where the water is motionless.
The influence of the ocean on the life of the planet
The role of ocean currents in the life of our planet can hardly be overestimated, since the movement of water flows directly affects the planet's climate, weather, marine organisms. Many people compare the ocean to a huge heat engine powered by solar energy. This machine creates an incessant water exchange between the surface and deep layers of the ocean, providing oxygen dissolved in water and affecting the life of marine life.
This process can be traced, for example, considering the Peruvian current, which is located in the Pacific Ocean. Due to the rise of deep waters, which raise phosphorus and nitrogen upward, animal and plant plankton successfully develop on the ocean surface, as a result of which the food chain is organized. Plankton is eaten by small fish, which, in turn, become a prey to larger fish, birds, marine mammals, which, with such an abundance of food, settle here, making the region one of the most highly productive regions of the World Ocean.
It also happens that the cold current becomes warm: the average ambient temperature rises by several degrees, which is why warm tropical showers are poured onto the ground, which, once in the ocean, destroy the fish accustomed to the cold temperature. The result is disastrous - in the ocean there is a huge amount of dead small fish, large fish leave, fishing stops, birds leave their nesting sites. As a result, the local population is deprived of fish, crops that have been beaten by rainstorms, and profits from the sale of guano (bird droppings) as fertilizer. The restoration of a former ecosystem can often take several years.
How does the temperature of surface waters in the oceans change?
The temperature of the surface waters of the world's oceans decreases in the direction from the equator to the poles.
What determines the density of the waters of the World Ocean?
The density of the world's oceans depends on temperature and salinity.
Find the largest warm and cold currents in the picture.
Consider the impact of warm and cold ocean currents on coastal nature.
Warm and cold currents affect the climate and nature of the coasts. So, warm currents increase the air temperature by and increase the amount of precipitation. Cold currents lower temperatures and reduce precipitation.
Questions and tasks
1. What is current?
Flow is the movement of water in a horizontal direction.
The warm current has a water temperature several degrees higher than the surrounding ocean water. Cold current - On the contrary. Warm currents are usually directed from warmer latitudes to colder ones, and colder ones - vice versa.
3. What are the main reasons for the formation of currents.
The main reason for the appearance of surface currents is wind. When it touches the water surface, it entails water. In the depths of the seas and oceans, currents are formed due to differences in the density of the water.
4. Find and point to physical map the world's largest ocean currents, listed in the text of the paragraph.
Warm currents - South and North trade winds, Monsoon, Gulf Stream, North Atlantic, Brazilian.
Cold currents - current of the Western winds, Peruvian, Labrador.
5. Using Figure 154, trace the possible movement paths for a sealed bottle that was dropped from a ship off the western coast of South America.
A sealed bottle thrown into the water off the western shores of South America will enter the Peruvian Current and head north towards the equator. At the equator, the bottle falls into the South Tradewind Current. It will carry the bottle to the shores of Australia or New Guinea.
6. What is the significance of currents for the climate of the Earth, plants and animals of the ocean?
Ocean currents affect the climate and nature of the Earth. They redistribute heat and cold between latitudes. Warm currents bring warmth from tropical latitudes to temperate and arctic ones. Cold currents return cold water to the equator. The North Atlantic Current is the main reason for the mild climate of Northern Europe. Thanks to currents in the oceans and seas, not only heat is redistributed, but also dissolved nutrients and gases. Living organisms get more opportunities for development. With the help of currents, plants and animals move and populate new territories.
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