Australia and other tropical climates. What climate zones is Australia located in - description, features and interesting facts
Ocean or sea currents are forward motion water masses in the oceans and seas caused by by various forces. Although the most significant cause of currents is wind, they can also be formed due to uneven salinity individual parts ocean or sea, differences in water levels, uneven heating of different areas of water areas. In the depths of the ocean there are eddies created by bottom irregularities; their size often reaches 100-300 km in diameter, they capture layers of water hundreds of meters thick.
If the factors causing currents are constant, then a constant current is formed, and if they are episodic in nature, then a short-term, random current is formed. According to the predominant direction, currents are divided into meridional, carrying their waters to the north or south, and zonal, spreading latitudinally - approx. Currents in which the water temperature is higher than the average temperature for the same latitudes are called warm, below - cold, and currents, having the same temperature as the surrounding waters are neutral.
Monsoon currents change direction from season to season, depending on how the offshore monsoon winds blow. Countercurrents move towards neighboring, more powerful and extended currents in the ocean.
The direction of currents in the World Ocean is influenced by the deflecting force caused by the rotation of the Earth - the Coriolis force. In the Northern Hemisphere, it deflects currents to the right, and in the Southern Hemisphere, to the left. The speed of currents on average does not exceed 10 m/s, and their depth extends to no more than 300 m.
In the World Ocean there are constantly thousands of large and small currents that circle the continents and merge into five giant rings. The system of currents in the World Ocean is called circulation and is associated primarily with the general circulation of the atmosphere. Ocean currents redistribute solar heat absorbed by masses of water. Warm water, heated sun rays at the equator, they are transported to high latitudes, and cold water from the polar regions, thanks to currents, it flows to the south. Warm currents contribute to an increase in air temperature, and cold currents, on the contrary, reduce it. Territories washed by warm currents have a warm and humid climate, while those near which cold currents pass have a cold and dry climate.
The most powerful current The World Ocean is a cold current of the Western Winds, also called the Antarctic Circumpolar (from the Latin cirkum - around - approx.. The reason for its formation is strong and stable westerly winds, blowing from west to east over vast areas of the Southern Hemisphere from temperate latitudes to the coast of Antarctica. This current covers an area 2,500 km wide, extends to a depth of more than 1 km and transports up to 200 million tons of water every second. There are no large land masses along the path of the Western Winds, and it connects the waters of three oceans - the Pacific, Atlantic and Indian - in its circular flow.
The Gulf Stream is one of the largest warm currents Northern hemisphere. It passes through the Gulf of Mexico (English Gulf Stream - Gulf Current) and carries warm tropical waters Atlantic Ocean to high latitudes. This gigantic flow of warm water largely determines the climate of Europe, making it soft and warm. Every second the Gulf Stream carries 75 million tons of water (for comparison: the Amazon, the most deep river in the world - 220 thousand tons of water). At a depth of about 1 km, a countercurrent is observed under the Gulf Stream.
UPWELLING
In many areas of the World Ocean, deep waters “float” to the surface of the sea. This phenomenon, called upwelling (from the English up - up and well - gushing - approx.), occurs, for example, if the wind drives away warm surface waters, and colder ones rise in their place. The water temperature in upwelling areas is lower than the average at a given latitude, which creates favorable conditions for the development of plankton, and therefore other marine organisms - fish and marine animals that feed on them. Upwelling areas are the most important fishing areas of the World Ocean. They are located off the western shores of the continents: Peruvian-Chilean - near South America, Californian - in North America, Benguela - in South-West Africa, Canary - in West Africa.
Which moves with a certain cyclicity and frequency. Characterized by consistency physical and chemical properties and specific geographic location. It can be cold or warm depending on the hemisphere. Each such flow is characterized by increased density and pressure. The flow of water masses is measured in sverdrup, in more in a broad sense- in units of volume.
Types of currents
First of all, cyclically directed water flows are characterized by such characteristics as stability, speed of movement, depth and width, chemical properties, influencing forces, etc. Based on the international classification, flows come in three categories:
1. Gradient. Occur when exposed to isobaric layers of water. A gradient ocean current is a flow that is characterized by horizontal movements of isopotential surfaces of the water area. Based on their initial characteristics, they are divided into density, pressure, drain, compensation and seiche. As a result of the waste flow, sediments and ice melt occur.
2. Wind. Determined by the slope of the sea level, the strength air flow and fluctuations in mass density. A subspecies is drift. This is a flow of water caused purely by the action of the wind. Only the surface of the pool is subject to vibrations.
3. Tidal. They appear most strongly in shallow waters, at river mouths and near the coast.
A separate type of flow is inertial. It is caused by the action of several forces at once. Based on the variability of movement, constant, periodic, monsoon and trade wind flows are distinguished. The last two are determined by direction and speed seasonally.
Causes of ocean currents
IN present moment Water circulation in the world's waters is just beginning to be studied in detail. By by and large, specific information is known only about surface and shallow currents. The main problem is that the oceanographic system does not have clear boundaries and is located in constant movement. It is a complex network of flows, determined by various physical and chemical factors.
Nevertheless, the following causes of ocean currents are known today:
1. Cosmic influence. This is the most interesting and at the same time difficult process to study. In this case, the flow is determined by the rotation of the Earth, the impact of cosmic bodies on the atmosphere and hydrological system of the planet, etc. A striking example is the tides.
2. Exposure to wind. Water circulation depends on strength and direction air masses. In rare cases, we can talk about deep currents.
3. Density difference. Streams are formed due to the uneven distribution of salinity and temperature of water masses.
Atmospheric exposure
In the world's waters, this kind of influence is caused by the pressure of heterogeneous masses. Coupled with space anomalies, water flows in the oceans and smaller basins change not only their direction, but also their power. This is especially noticeable in the seas and straits. A striking example The Gulf Stream can serve. At the beginning of its journey, it is characterized by increased speed.
The Gulf Stream is accelerated by both contrary and favorable winds. This phenomenon forms a cyclic pressure on the layers of the pool, accelerating the flow. From here, at a certain period of time, there is a significant outflow and inflow large quantity water. The weaker the atmospheric pressure, the higher the tide.
As water levels drop, the slope of the Straits of Florida becomes smaller. Because of this, the flow speed is significantly reduced. Thus, we can conclude that high blood pressure reduces the flow force.
Exposure to wind
The connection between the flows of air and water is so strong and at the same time simple that it is hard not to notice even with the naked eye. Since ancient times, sailors have been able to calculate the appropriate ocean current. This became possible thanks to the work of scientist W. Franklin on the Gulf Stream, dating back to the 18th century. Several decades later, A. Humboldt indicated the wind in the list of the main extraneous forces affecting water masses.
From a mathematical point of view, the theory was substantiated by the physicist Zeppritz in 1878. He proved that in the World Ocean there is a constant transfer of the surface layer of water to deeper levels. In this case, the main force influencing the movement is the wind. The flow speed in this case decreases in proportion to the depth. The defining condition constant circulation water is endless for a long time wind action. The only exceptions are trade wind air flows, which cause the movement of water masses in the equatorial zone of the World Ocean seasonally.
Density difference
The impact of this factor on water circulation is the most important reason currents in the World Ocean. Large-scale studies of the theory were carried out by the international Challenger expedition. Subsequently, the scientists' work was confirmed by Scandinavian physicists.
The heterogeneity of water mass densities is the result of several factors. They have always existed in nature, representing a continuous hydrological system of the planet. Any deviation in water temperature entails a change in its density. In this case, the opposite is always observed proportional dependence. The higher the temperature, the lower the density.
The difference in physical indicators is also affected by physical state water. Freezing or evaporation increases density, precipitation decreases it. Affects the strength of the current and the salinity of water masses. It depends on melting ice, precipitation and evaporation levels. In terms of density, the World Ocean is quite uneven. This applies to both surface and deep layers of the water area.
Pacific Currents
The general flow pattern is determined by atmospheric circulation. Thus, the eastern trade wind contributes to the formation of the Northern Current. It crosses the waters from the Philippine Islands to the coast Central America. It has two branches that feed the Indonesian Basin and the Pacific Equatorial Ocean Current.
The largest currents in the water area are the Kuroshio, Alaska and California currents. The first two are warm. The third current is the cold ocean current of the Pacific Ocean. The basin of the Southern Hemisphere is formed by the Australian and Trade Wind currents. The Equatorial Countercurrent is observed just east of the center of the water area. Off the coast of South America there is a branch of the cold Peruvian Current.
IN summer time in the region of the equator there is an oceanic El Niño current. It pushes aside the cold masses of water of the Peruvian Stream, forming a favorable climate.
Indian Ocean and its currents
The northern part of the basin is characterized by seasonal change warm and cold currents. This constant dynamics is caused by the action of the monsoon circulation.
IN winter period dominated by the South-Western Current, which originates in the Bay of Bengal. A little further south is Western. This oceanic current of the Indian Ocean crosses the waters from the coast of Africa to Nicobar Islands.
In summer, the east monsoon contributes to a significant change surface waters. The equatorial countercurrent shifts to depth and noticeably loses its strength. As a result, its place is taken by powerful warm Somali and Madagascar currents.
Circulation of the Arctic Ocean
The main reason for the development of the underwater current in this part of the World Ocean is the powerful influx of water masses from the Atlantic. The fact is that the centuries-old cover of ice does not allow the atmosphere and cosmic bodies to influence the internal circulation.
The most important current in the Arctic Ocean is the North Atlantic. It brings in huge volumes of warm masses, preventing the water temperature from dropping to critical levels.
The Transarctic Current is responsible for the direction of ice drift. Of the others, the most large flows we can distinguish the Yamal, Spitsbergen, North Cape and Norwegian currents, as well as a branch of the Gulf Stream.
Atlantic Basin Currents
The salinity of the ocean is extremely high. The zonality of water circulation is the weakest among other basins.
The main ocean current here is the Gulf Stream. Thanks to it, the average water temperature remains at +17 degrees. This oceanic warmth warms both hemispheres.
Also, the most important currents in the basin are the Canary, Brazilian, Benguela and Trade Wind currents.
Mariners learned about the presence of ocean currents almost as soon as they began to plow 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 were made, for example, Christopher Columbus sailed to America thanks to the North Equatorial Current. After this, not only sailors, but also scientists began to pay close attention to ocean currents and strive to study them as best and deeply as possible.
Already in the second half of the 18th century. the sailors studied the Gulf Stream quite well and successfully applied their knowledge in practice: from America to Great Britain they went with the flow, and in reverse direction adhered to certain distance. This allowed them to stay two weeks ahead of ships whose captains were not familiar with the area.
Ocean or sea currents are large-scale movements of water masses in the World Ocean at speeds from 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 several thousand.
It has been established that water flows do not move straight, but deviate slightly to the side and are subject to the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere it’s the other way around.. At the same time, currents located in tropical latitudes(they are called equatorial or trade winds), move mainly from east to west. The strongest currents were recorded along eastern shores continents.
Water flows do not circulate on their own, but are set in motion sufficient quantity factors - wind, rotation of the planet around its axis, gravitational fields of the Earth and the Moon, bottom topography, outlines of continents and islands, differences in the temperature of water, its density, depths in different places of the ocean and even its physical and chemical composition.
Of all kinds 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 the western east direction. These trade winds form the huge flows 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 opposite direction from the movement of air masses). Most of them, when colliding with continents and islands, turn to the north or south.
Warm and cold water currents
It must be taken into account that the concepts of “cold” or “warm” currents are conditional definitions. So, despite the fact that the temperature of the water flows of the Benguela Current, which flows along the Cape of Good Hope, is 20 ° C, it is considered cold. But the North Cape Current, which is one of the branches of the Gulf Stream, with temperatures from 4 to 6 ° C, is warm.
This happens because cold, warm and neutral currents got their names based on a comparison of the temperature of their water with the temperature of the surrounding ocean:
- 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, due to high river flows, ocean water has a reduced salinity of surface waters;
- If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from tropical to subpolar latitudes, for example, the Gulf Stream.
Main water flows
On at the moment Scientists have recorded about fifteen main ocean 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 the West Greenland, West Spitsbergen and Norwegian, are warm, and only the East Greenland is a cold current.
But almost all oceanic currents of the Indian Ocean are warm or neutral, with the Monsoon, Somali, Western Australian and Cape Agulhas current (cold) moving 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 because, together with seasonal monsoon winds, which change their direction twice a year, oceanic rivers also change their course: in winter they mainly flow to the west, in summer - to the east (a phenomenon characteristic only of the Indian Ocean).
Since the Atlantic Ocean stretches from north to south, its currents also have meridional direction. Water flows located in the north move clockwise, in the south - counterclockwise.
A striking example of the flow of the Atlantic Ocean is the Gulf Stream, which, starting in the Caribbean Sea, carries warm waters to the north, breaking up into several side streams along the way. 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 join the Gulf Stream, forming a vicious circle.
The currents of the Pacific Ocean are mainly latitudinal and form two huge circles: northern and southern. Since the Pacific Ocean is extremely large, it is not surprising that its water flows have a significant impact on most of of our planet.
For example, trade wind water flows transport warm waters from the western tropical shores to the eastern ones, which is why 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
Enough long time Scientists believed that deep ocean waters were almost motionless. But soon special underwater vehicles were discovered on great depth both slow and fast flowing water streams.
For example, under the Equatorial Current of the Pacific Ocean at a depth of about one hundred meters, scientists have identified the underwater Cromwell Current, moving eastward at a speed of 112 km/day.
Soviet scientists found a similar movement of water flows, but in the Atlantic Ocean: the width of the Lomonosov Current is about 322 km, and maximum speed 90 km/day was recorded at a depth of about one hundred meters. After this, another underwater flow was discovered in the Indian Ocean, although its speed turned out to be 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 of why they appeared, how they were formed, and whether the entire area of the ocean is covered by currents or there is a point where the water is still.
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, and marine organisms. Many compare the ocean to a huge heat engine driven by solar energy. This machine creates a constant exchange of water between the surface and deep layers of the ocean, providing it with oxygen dissolved in the water and influencing the life of marine inhabitants.
This process can be traced, for example, by considering Peruvian Current what is in Pacific Ocean. Thanks to the rise of deep waters, which lift phosphorus and nitrogen upward, animal and plant plankton successfully develop on the ocean surface, resulting in the organization food chain. Plankton eats small fish, which, in turn, becomes a victim of larger fish, birds, marine mammals, which, given such food abundance, settle here, making the region one of the most highly productive areas of the World Ocean.
It also happens that a cold current becomes warm: average temperature environment rises by several degrees, which is why warm tropical showers spill onto the ground, which, once in the ocean, kill fish that are accustomed to cold temperature. The result is disastrous - it ends up in the ocean huge amount dead small fish, big fish goes away, fishing stops, birds leave their nesting grounds. As a result local population loses fish, rain-damaged crops, and profits from the sale of guano ( bird droppings) as a fertilizer. It can often take several years to restore the previous ecosystem.
Geography lesson V 7th grade e
Topic: “Ocean Currents”
Target: reveal the reasons for the circular movement of surface waters, give an idea of general scheme surface currents in the World Ocean.
Tasks:
To form an idea of ocean currents, the reason for their occurrence, types of currents and their use.
identify general patterns ocean currents
Continue training in working with contour maps, identifying patterns, reading atlas maps.
To cultivate an aesthetic perception of geographical objects
Equipment: textbook, atlas, ocean map, physical map hemispheres, presentation, geographical simulator, test, portraits of travelers (H. Columbus, T. Heyerdahl).
Main content: ocean currents. Reasons for the formation of ocean currents. Types of ocean currents. The main surface currents of the World Ocean. The importance of ocean currents.
Lesson type:
combined.
PROGRESS OF THE LESSON
Organizational moment
Good morning guys! Take a seat, check your readiness for the lesson, that everything is in place. Today we have not just a lesson - today we have a holiday, because guests came to us - geography teachers from all over our region. We were expecting guests, and today, putting aside all preparatory worries, let's plunge into the world of the wonderful science of geography.
Checking homework.
In the last lesson, we studied the topic...climatic zones and regions of the earth. Let's remember what we talked about in the last and previous lessons.
1. Perform at the board individual assignment will do
Draw a diagram atmospheric circulation using colored crayons (Task Card, blue, red and green chalk)
2.An individual test of our geographic simulator on questions will be completed on a laptop
3.And let’s remember what a climate zone is?
Climate zone –
What are the different climate zones? (main and transitional)
What prefix do we use to denote the transitional climate zone (Sub)
How many main belts? (7)
Name the main climatic zones (equatorial, tropical, temperate, Arctic, Antarctic)
Show the main climate zones on the map...
How many transition belts? (6)
Name the transitional climatic zones (2 subequatorial, 2 subtropical, subarctic, subantarctic)
Show on the map transition belts…
What is the difference between main and transition belts.
Do all zones have climatic regions (no)
In which climate zone there are no climatic regions
Name and show them on the area map temperate zone Eurasia (moderate continental, continental, sharply continental, monsoon)
4. Let’s listen to what you wrote in your home mini-essay “I would like to live in the ...... belt, because .....
Let's see how you coped with the task... test completed
Updating knowledge
You and I remembered what we studied and it’s time for us to turn to new material, but it will not be entirely new for us. In the 6th grade, we already became acquainted with the peculiarities of the nature of the Earth.
And today we will move from atmospheric processes to water ones.
What's it called water shell Earth? (hydrosphere)
And the symbol of our lesson will be this picture . It depicts the famous Norwegian traveler Thor Heyerdahl. (photo)
In 1947, he and 5 like-minded people built a raft of 9 balsa wood logs and named it Kon-Tiki. In 101 days the brave navigator crossed over Pacific Ocean.
And in 1969, he undertook a new dangerous expedition to prove the possibility of African peoples crossing the Atlantic Ocean.
He and six of his followers built a boat from papyrus and named it "Ra". Their first trip was unsuccessful. On next year They again went out to the ocean on a papyrus boat and this time reached their goal in 57 days.
Let's look at the map: Thor Heyerdahl sailed by boat from the port of Safi (32 0 With. w. and 9 0 h. d.) to the island of Barbados (13 0 With. w. and 59 0 h. d.). Follow its route on a map of the oceans. What helped the traveler along the way?
A good way to travel is to travel with the help of ocean currents. And in order to use it, you need to get acquainted with the currents
The topic of our lesson, you guessed it– ocean currents
Let's open our notebooks and write down the date and topic of our lesson.
What do you guys think, what questions do we face in this topic?
What are ocean currents?
What types of currents are there?
How are they formed?
How do people use ocean currents?
To get answers to the questions that interest us, we need to turn to our main source of knowledge. What is this? Textbook. Let's open the textbook page and find and read what an ocean current is.
Ocean current -
People have known about ocean currents for a long time. Historical information prepared for us...
(MESSAGE ABOUT THE HISTORY OF THE DISCOVERY OF OCEAN CURRENTS)
What causes the formation of ocean currents in the World Ocean?
VIDEO
What reason leads to the formation of currents (due to the influence constant winds). What constant winds do we know? (Task at the board)But there are several other reasons that affect the direction of currents:
1. Constant winds.2. Outlines of continents.
3. Bottom topography
4
. The rotation of the Earth around its axis.
Let's turn to another reliable source geographic information– map. How are ocean currents shown on a map? (arrows)
The North Atlantic Current off the coast of Scandinavia has a temperature of +10 0
S. What kind of current is this?(
Warm)
And the Peruvian Current off the coast of South America has a temperature of +19 0 S, what is it? (Cold).
What's the contradiction? (+10 0 C - warm, + 19 0 C – cold)What is the question?
Which currents are called cold and which are called warm?
Let's work and fill out the table you have on your desk
Let's write it down
Current name
Color on the map
Current water temperature
Ocean surface temperature
Temperature comparison
Current type
North Atlantic
red
warm
Peruvian
blue
cold
Conclusion: A current is cold if its temperature is several degrees lower than the temperature of the surrounding ocean water….
Read the page in the textbook and compare whether we made the right conclusion?
- Warm current - This is a current whose water temperature is several degrees higher than the temperature of the surrounding water.
- Cold current - This is a current whose temperature is several degrees lower than the surrounding water.
Find on the map and mark the following currents: Gulf Stream, Canary, Peruvian, Labrador Current Western winds, Kuroshio.
Which ones are warm? Cold? What pattern did you notice in the arrangement of these currents? ( Warm currents move from the equator, cold currents move from the poles, close, and flow counterclockwise.)
Look carefully at the map. What conclusions can be drawn by analyzing current patterns in the northern and southern hemispheres?
The direction of currents clockwise and counterclockwise is influenced by the rotation of the Earth around its axis. North of the equator, currents bend to the right, south of the equator, to the left. This phenomenon is called the Coriolis effect, named after the French mathematician Gaspard de Coriolis who described it. This is a law of physics and you will study it in high school. In the northern hemisphere, currents travel clockwise, while in the southern hemisphere they travel counterclockwise.
Fizminutka
Let us take a break from our research and warm up. What phenomena can be found in the ocean? Waves, storm, hurricane, tsunami... Let's try to depict these phenomena... wave... higher... the storm begins... A hurricane... during a sea earthquake a tsunami is formed... quieter, quieter.... We moor to the shore... that is, at the desk. Let's warm up... Let's continue.
– Are all currents driven by wind?
If the flow of water encounters an obstacle (land or rising bottom relief), it divides, going around the obstacle with different sides. The flow also, if it encounters an obstacle, is most often divided into twosewage currents
– When the West Wind Current, which is a wind current, collides, one drain current is formed, and the West Wind Current continues to move on. But there are cases when the wind current ceases to exist as a result of a collision with the mainland, and instead of it two waste currents are formed. Find examples on the map.(California and Alaska, East Australian and Inter-trade, Kuroshio and Inter-trade.)
Apply to contour maps two waste streams with thicker arrows.
From what current is ... flow formed?
- Find the current of the Western Winds on the ocean map. Which oceans does it cross?
(VIDEO ABOUT THE CURRENT OF WESTERN WINDS)
Poem about the Current of the West Winds
Antarctica past Australia, America and Africa
Past all possible islands...
Everyone is sailing, my boats are sailing
Along the course of the Western winds.
I'll draw it on a worn map
This amazing route
In the blue of the vast expanse
Everyone is sailing, the boats are sailing.
Speaking about ocean currents, it seems to me that it will be very useful to know the peculiarities of the current of our native sea.
What sea am I talking about? (Black)
Which ocean basin does it belong to (Atlantic)
Help us learn about the currents of the Black Sea...
Black Sea Currents
The main current of the Black Sea is the Main Black Sea Current. It is directed counterclockwise and forms two noticeable rings (“Knipovich glasses”, this name is associated with the Russian hydrologist Nikolai Knipovich, who described this current). The current is very changeable. IN coastal waters In the Black Sea, eddies of the opposite direction are formed - anticyclonic currents.
Who likes to swim in the sea in summer? Why?
Water procedures very useful, but know that the sea is fraught with danger.... Please….
Secrets of the Black Sea
When swimming in the Black Sea, you should be aware of the existence of a local Black Sea current - “ draft». In the world, such a phenomenon is called RIP.
Most often, this current is formed during a storm near sandy shores. The water flowing onto the shore does not return evenly, but in streams along the channels formed in the sandy bottom.
Getting caught in the jet's current is dangerous: it can be carried out to the open sea. To get out of the tug, you need to swim not straight to the shore, but at an angle to reduce the resistance of receding water.
V. Stage of consolidation of knowledge
We have practically dealt with the material. Let's remember what we wanted to know...
Have we received answers... But we don’t know everything. You can supplement your knowledge by completing homework, which let's write down in our diary.VI. Homework
1. Study &20., describe one of the currents according to the plan p.572.Creativeexerciseprepare a report on the currentEl Niño
1.What has the greatest influence on the formation of currents in the ocean
B) earthquakes
B) the gravity of the moon
2. What types of currents are there?
A) warm
B) cold
B) warm and cold
3. What currents begin at the equator
A) warm
B) cold
B) warm and cold
4. What are the influences of ocean currents?
A) on climate formation
B) on the formation of the ocean floor topography
B) on the rotation of the Earth
5.Name the largest cold current
A) Gulf Stream
B) Current of the Western winds
B) Peruvian Current
VII. Summing up results lesson A
Did you like the lesson?
What made an impression?
What did you like most?
I liked your work in class and I want to evaluate it
History of the discovery of surface currents
First mention of existence sea currents found even among ancient Greek scientists; Aristotle in his writings talks about currents in the Kerch, Bosporus and Dardanelles straits. And the Carthaginians had some idea about the Sargasso Sea.
It is known that in the Middle Ages the Norwegians discovered a sea route from northern Europe first to Iceland and then to Greenland and North America. On these voyages the Normans became familiar with sea currents. This is clear from the names they gave to noticeable places they encountered along the way, such as: Fr. Currents, Currents Bay, Currents Cape.
The Arabs sailed a lot Indian Ocean and installed sea communication with China, Mesopotamia and Egypt. They were familiar with monsoon currents.
The Portuguese, while moving south along the coast of Africa, became acquainted with the Guinea and Bengal Currents, and Vasco da Gama at the end of the 15th century, during his first voyage to India, noticed the Mozambique Current.
First observations of ocean currents
The first detailed observation of currents in the open ocean was made by Christopher Columbus during his first voyage to America, on September 13, 1492 in the region of 27° N. w. and 40° W. d. By the deviation of the lot, lowered deep into the water, he noticed that the ship was being carried by the current to the SW. Columbus's subsequent voyages introduced him even more to the North Equatorial Current and gave him the opportunity to suggest that the waters of the ocean along the equator move “together with the vault of heaven” to the west. On his fourth voyage (1502-1504), Columbus discovered a current running along the coast of Honduras.
In the oceans and seas, huge streams of water tens and hundreds of kilometers wide and several hundred meters deep move in certain directions over distances of thousands of kilometers. Such flows - "in the oceans" - are called sea currents. They move at a speed of 1-3 km/h, sometimes up to 9 km/h. Reasons causing currents, several: for example, heating and cooling of the water surface, and evaporation, differences in water density, but the most significant role in the formation of currents is.
Currents, according to their prevailing direction, are divided into those going to the west and east, and meridional - carrying their waters to the north or south.
IN separate group identify currents that go towards neighboring, more powerful and extended ones. Such flows are called countercurrents. Those currents that change their strength from season to season depending on the direction of coastal winds are called monsoon currents.
Among the meridional currents, the Gulf Stream is the most famous. It transports on average about 75 million tons of water every second. For comparison, we can point out that the deepest one carries only 220 thousand tons of water every second. The Gulf Stream transports tropical waters to temperate latitudes, largely determining the life of Europe. It was thanks to this current that it got soft, warm climate and became the promised land for civilization, despite its northern location. Approaching Europe, the Gulf Stream is no longer the same stream that breaks out of the Gulf. Therefore, the northern continuation of the current is called. Blue waters are replaced by more and more green ones. Of the zonal currents, the most powerful is the current of the Western winds. In the vast expanse of the Southern Hemisphere there are no significant land masses off the coast. Strong and steady westerly winds prevail over this entire area. They intensively transport ocean waters in an easterly direction, creating the most powerful current of the Western winds in all. It connects the waters of three oceans in its circular flow and transports about 200 million tons of water every second (almost 3 times more than the Gulf Stream). The speed of this current is low: to bypass Antarctica, its waters need 16 years. The width of the flow of the Western winds is about 1300 km.
Depending on the water, currents can be warm, cold or neutral. The water of the former is warmer than the water in the region of the ocean through which they pass; the latter, on the contrary, are colder than the water surrounding them; still others do not differ from the temperature of the waters through which they flow. As a rule, currents moving away from the equator are warm; the currents flowing are cold. They are usually less salty than warm. This is explained by the fact that they flow from areas with a large number precipitation and less evaporation or from areas where the water is desalinated by melting ice. Cold currents in parts of the oceans are formed due to the rise of cold deep waters.
An important regularity of currents in the open ocean is that their direction does not coincide with the direction of the wind. It deviates to the right in the Northern Hemisphere and to the left in Southern Hemisphere from the wind direction at an angle of up to 45°. Observations show that in real conditions the deviation at all latitudes is slightly less than 45°. Each underlying layer continues to deviate to the right (left) from the direction of movement of the overlying layer. At the same time, the flow speed decreases. Numerous measurements have shown that currents end at depths not exceeding 300 meters. The significance of ocean currents lies primarily in their redistribution on Earth solar heat: Warm currents raise the temperature, while cold currents lower it. Currents have a huge impact on the distribution of precipitation on land. Territories washed by warm waters, always have humid climate, and cold ones are dry; in the latter case, rains do not fall; they only have a moisturizing value. Living organisms are also transported with currents. This primarily applies to plankton, followed by large animals. When we meet warm currents With cold water, ascending currents of water are formed. They raise deep water, rich in nutritious salts. This water favors the development of plankton, fish and marine animals. Such places are important fishing grounds.
The study of sea currents is carried out both in the coastal zones of the seas and oceans, and in the open sea by special sea expeditions.