Mariners about availability ocean currents learned almost immediately, as soon as they began to plow the waters of the oceans. 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 explore them as best and as deeply as possible.

Already in the second half of the XVIII century. 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 kept a certain distance. This allowed them to be two weeks ahead of ships whose captains were not familiar with the terrain.

Ocean or sea currents are called large-scale movements water masses World Ocean at a speed of 1 to 9 km / h. These streams do not move randomly, but in a certain channel and direction, which is main reason why they are sometimes called the 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 has been established that water flows do not move straight, but deviating slightly to the side, they obey the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere it is vice versa.. 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 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 - the wind, the rotation of the planet around its axis, gravitational fields The Earth and the Moon, the bottom topography, the outlines of the continents and islands, the difference in temperature indicators of water, its density, depth in different parts of the ocean, and even its physical and chemical composition.

Of all kinds water streams 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 eastbound. These trade winds form huge streams of the North and South Equatorial currents near the equator. 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 air masses side). Most, colliding with the continents and islands, turns to the north or south.

Warm and cold water streams

It must be taken into account 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 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 the cold, warm and neutral currents got their names based on a comparison of 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 waters surrounding it, 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 (for example, the Labrador Current), or from areas where, due to the large flow of rivers, ocean water has low salinity surface water;
• If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from the tropics to subpolar latitudes, such as the Gulf Stream.

Main water flows

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 North Arctic Ocean.

It is interesting that all the currents of the Arctic Ocean move at the same speed - 50 cm / s, three of them, namely the West Greenland, West Svalbard and Norwegian, are warm, and only the 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, West Australian and the Cape of Needles (cold) move at a speed of 70 cm / s, the speed of the rest varies from 25 to 75 cm / s. The water flows of this ocean are interesting because, along with the seasonal monsoon winds, which change their direction twice a year, ocean rivers also change their course: in winter they mainly flow west, in summer - east (a phenomenon characteristic only of 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 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 end up in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of a 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: northern and southern. Insofar as Pacific Ocean extremely large, it is not surprising that its water flows have a significant impact on most our planet.

For example, trade-wind water flows distill warm water from the western tropical coasts to the eastern ones, which is why in the tropical zone West Side 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 the deep ocean waters are almost motionless. But soon, special underwater vehicles discovered both slow and fast-flowing water flows at great depths.

For example, under the Equatorial Pacific Ocean at a depth of about one hundred meters, scientists have identified the Cromwell underwater stream, 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 maximum speed at 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 of which is the question of why they appeared, how they formed, and whether the entire ocean area 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 cannot 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, which is set in motion by solar energy. This machine creates an unceasing exchange of water between surface and deep layers ocean, providing it with oxygen dissolved in water and affecting the life of marine life.

This process can be traced, for example, by considering the Peruvian Current, which is located in the Pacific Ocean. Thanks to the rise of deep waters, which raise phosphorus and nitrogen upwards, animal and plant plankton successfully develop on the ocean surface, as a result of which food chain. Plankton is eaten by small fish, which, in turn, becomes a victim of larger fish, birds, marine mammals, which, with 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: the average temperature environment rises by several degrees, causing warm tropical showers to fall on the ground, which, once in the ocean, destroy fish accustomed to cold temperature. The result is deplorable - a huge amount of dead small fish ends up in the ocean, large fish leave, fishing stops, birds leave their nests. As a result, the local population is deprived of fish, crops that were beaten by downpours, and profits from the sale of guano (bird droppings) as fertilizer. It can often take several years to restore the former ecosystem.

As observations show, the layers of the World Ocean move in the form of huge streams tens and hundreds of kilometers wide and thousands of kilometers long. These flows are called currents. They move at a speed of about 1-3 km/h, sometimes up to 9 km/h.

Currents are caused by the action of the wind on water surface gravity and tidal forces. The flow is influenced by the internal friction of water and the Coriolis force. The first slows down the flow and causes eddies at the boundary of the layers with different density, the second changes its direction.

Classification of currents. According to their origin, they are divided into frictional, gravity-gradient and tidal. In frictional flows, drift, caused by constant or prevailing winds; they are of the greatest importance in the circulation of the waters of the oceans.

Gravity-gradient currents are subdivided into stock(waste) and density. Stock flows occur in the case of a steady rise in the water level caused by its inflow (for example, the inflow of Volga water into the Caspian Sea) and an abundance of precipitation, or in the case of a drop in the level due to the outflow of water and its loss to evaporation (for example, in the Red Sea). Density currents are the result of unequal density of water at the same depth. They arise, for example, in straits connecting seas with different salinities (for example, between the Mediterranean Sea and the Atlantic Ocean).

Tidal currents are created by the horizontal component of the tidal force.

Depending on the location in the water column, currents are distinguished superficial, deep and bottom.

According to the duration of existence, currents can be distinguished permanent, occasional and temporary. Constant currents from year to year retain the direction and speed of the current. They can be caused by constant winds, such as trade winds. The direction and speed of periodic currents change in accordance with the change in the causes that caused them, for example, monsoons, tides. Temporal currents are caused by random causes.

Currents can be warm, cold and neutral. The former are warmer than the water in the region of the ocean through which they pass; the latter are colder than the surrounding water. As a rule, currents moving away from the equator are warm, while currents moving towards the equator are cold. Cold currents are usually less salty than warm ones. This is because they flow from areas with more precipitation and less evaporation, or from areas where the water is freshened by melting ice.

Distribution patterns surface currents. The picture of the surface currents of the World Ocean was established in the main features by XX century. The direction and speed of the current were determined mainly from observations of the movement of natural and artificial floats (fin, bottles, drift of ships and ice floes, etc.) and from the difference in determining the place of the ship by the dead reckoning method and the method of observing heavenly bodies. The modern task of oceanology is detailed study currents throughout ocean water. This is done by various instrumental methods, in particular by radar. The essence of the latter is that a radio wave reflector is lowered into the water, and, fixing its movement on the radar, determine

direction and speed of the current.

The study of drift currents made it possible to derive the following regularities:

1) the speed of the drift current increases with the intensification of the wind that caused it and decreases with increasing latitude according to the formula

where BUT- wind coefficient equal to 0.013, W - wind speed, φ - latitude of the place;

2) the direction of the current does not coincide with the direction of the wind: it obeys the Coriolis force. Given sufficient depth and distance from the coast, the deviation is theoretically 45°, but in practice it is somewhat less.

3) the direction of the current is strongly influenced by the configuration of the banks. The current, heading towards the shore at an angle, bifurcates, and its large branch goes to the side obtuse angle. Where two currents approach the shore, a drain-compensation countercurrent arises between them due to the connection of their branches.

The distribution of surface currents in the World Ocean can be represented as the following schematic diagram (Fig. 42).

On both sides of the equator, trade winds cause north and south trade wind currents that deviate from the direction of the wind under the influence of the Coriolis force and move from east to west. Encountering on its way the eastern coast of the mainland, the trade winds bifurcate. Their branches, heading to the equator, meeting, form a drain-compensation countercurrent, following to the east between the trade wind currents. The branch of the northern trade wind current, deviated to the north, moves along the eastern shores of the mainland, gradually moving away from it under the influence of the Coriolis force. North of 30° N. sh. this current falls under the influence of the westerly winds prevailing here and moves from west to east. At western coasts mainland (about 50 ° N. Lat.), this current is divided into two branches, diverging in opposite sides. One branch goes to the equator, compensating for the loss of water caused by the northern trade wind current, and joins it, closing the subtropical ring of currents. The second branch follows north along the coast of the mainland. One part of it penetrates the Arctic Ocean, the other joins the current from the Arctic Ocean, completing another ring of currents. AT southern hemisphere just as in the northern one, a subtropical ring of currents arises. The second ring of currents is not formed, but instead of it there is a powerful drift current of westerly winds, connecting the waters of three oceans.

The actual distribution of surface currents in each ocean deviates from the principle scheme, since the outlines of the continents influence the direction of the currents (Fig. 43).

Propagation of ocean currents in depth. The movement of water caused by the wind on the surface is gradually transferred to the underlying layers due to friction. The flow velocity then decreases in geometric progression, and the direction of the flow under the influence of the Coriolis force deviates more and more from the initial one and at a certain depth turns out to be opposite to the surface one (Fig. 44). The depth at which the current turns 180° is called the friction depth. At this depth, the influence of the drift current practically ends. This depth is about 200 m. However, the action of the Coriolis force, which changes the direction of the flow, leads to the fact that, at a certain depth, the water jets either overtake the shores or are driven away from them, and then an angle of the surface of equal pressures arises near the shores, setting the entire water column in motion. This movement extends far from the coast. In connection with different conditions heating of the ocean surface at different latitudes, there is a convection of ocean water. In the equatorial region, an upward movement dominates, relatively more warm water, in the polar regions the downward movement is relatively more cold water. This should lead to the movement of water in the surface layers from the equator to the poles, and in the bottom layers from the poles to the equator.

In areas of high salinity, water tends to sink, in areas of low salinity, on the contrary, it tends to rise. The lowering and rising of water are also caused by surge and surge of water on the surface (for example, in the area of ​​action of the trade winds).

In deep ocean troughs, the water temperature rises by several tenths of a degree under the action of internal heat Earth. This results in vertical water currents. At the bottom of the continental slopes, powerful currents are observed with a speed of up to 30 m/s, caused by earthquakes and other causes. They carry a large amount of suspended particles and are called muddy streams.

The existence of systems of surface currents with a general direction of movement towards the center or from the center of the system leads to the fact that in the first case there is a downward movement of water, in the second - upward. An example of such areas can be subtropical ring systems currents.

Very small changes in salinity with depth and the constancy of salt composition at great depths indicate the mixing of the entire water column of the World Ocean. However, the exact picture

distribution of deep and bottom currents has not yet been established. Thanks to the continuous mixing of water, not only heat and cold are constantly transferred, but also nutrients required by organisms. In the zones of water subsidence, the deep layers are enriched with oxygen; in the zones of water uplift, biogenic substances (phosphorus and nitrogen salts) are carried from the depths to the surface.

Currents in the seas and straits. Currents in the seas are caused by the same reasons as in the oceans, but the limited size and shallower depths determine the scale of the phenomenon, and local conditions give them their distinctive features. Many seas (for example, the Black and Mediterranean) are characterized by a circular current due to the Coriolis force. In some seas (for example, in the White Sea), tidal currents are well expressed. In other seas (for example, in the North and Caribbean), sea currents are an offshoot of ocean currents.

According to the nature of the currents, straits can be divided into flowing and exchange straits. In flowing straits, the current is directed in one direction (for example, in Florida). In exchange straits, water moves in two opposite directions. Multidirectional streams of water can be one above the other (for example, in the Bosphorus and Gibraltar) or can be located next to each other (for example, La Perouse and Davis). In narrow and shallow straits, the direction may change to the opposite depending on the direction of the wind (for example, Kerch).

Currents can be divided into groups according to various external features, for example, there can be currents of a constant and periodic nature. The first from year to year go on average: in the same direction, they maintain their average speed and mass in the same places; the second is just changing specified properties periodically (monsoon currents). Random circumstances can also cause sometimes quite noticeable, but short-lived, or random, currents.

Ocean currents always represent the transfer of particles of water from one place in the ocean to another, and since water has a very large heat capacity, with such a transfer of particles, the particles lose their heat very slowly and, moreover, retain their salinity. Thus, the water of the currents always has different physical properties than that among which the current flows; moreover, if the temperature of the water flow is higher than that in the surrounding water, then the current is called warm, regardless of the number of degrees of its temperature. If the water temperature of the current is lower than the ambient temperature, then the current will be cold.

The current always captures a certain layer of water in depth, but there are currents that are completely imperceptible on the surface, but exist only at depth. The first are called surface, and the second - underwater, or deep.

Finally, there may be currents that go close to the bottom, then they are called bottom currents.

According to their origin, the currents are: drift, waste and compensatory (replenishing).

The name of drift currents refers to such movements of surface waters that arose solely as a result of friction (tangential - for an explanation, see Ekman's theory) of the wind on the water surface. Pure drift currents probably do not exist in the oceans, because there are always other causes that excite the movement of water; however, in cases where the influence of the wind, as the cause of the current, is the most important, then such a current is called drift. Further in the description of the currents, references to such cases are made in many places.

A flow is called a waste stream when it is a consequence of the accumulation of water, which in turn causes a change hydrostatic pressure at different locations on the same level surfaces at different depths. The accumulation of water can occur from various reasons: from the influence of winds, and from an excess of inflow of fresh water. river waters, or heavy precipitation, or melting ice. Finally, the change in hydrostatic pressure can also be affected by an uneven distribution (of density, and, therefore, in the same way be the cause of the occurrence of a waste flow.

A compensatory current is understood to be such a movement of water that makes up for the loss of water (i.e., a decrease in hydrostatic pressure) that has occurred for any reason in a certain area of ​​the ocean due to the outflow of water.

Vertical movements, constantly (occurring in the ocean, are called either convection movements, or simply the rise and fall of water.

Very diverse methods are used to study currents, they can be direct and mediocre. The direct ones include: comparison of the observed and countable places of the ship, determination of currents using turntables, floats, bottles, floating remains of ships that have crashed, floating natural objects (fin, algae, ice).

Among the mediocre, or indirect, methods of observing currents are: simultaneous observations of temperature and salinity, observations of the distribution of pelagic plankton or, in general, of the distribution of marine animals, since their existence depends on physical properties sea ​​water.

Most of these subjects can be applied to the study of underwater currents.

The main way to study surface currents is to compare the ship's positions obtained by observation, i.e., astronomical observations in latitude and longitude, with its positions, plotting the ship's courses sequentially on a map, and plotting the swum distances on the courses. Navigational data: the direction of the course and the speed of the ship are influenced by the movement of that surface layer of water, among which the ship makes its way, and therefore the surface current enters them in size and direction. Astronomical definitions of the place of the ship are independent of the influence of the current, therefore the observed place of the ship in the presence of a current never coincides with its calculated place.

If the astronomical and navigational methods of determining the location of the ship did not contain any errors, then, by connecting both places of the ship on the map, we would get the average direction of the current for a period of time from the place of the ship from where the course was started, until the moment astronomical observations were made. By measuring the line connecting the calculated and observed places of the ship, and dividing it by the number of hours in the above time interval, we obtain the average hourly current speed. Usually "in the courts merchant fleet astronomical observations are made once a day, and (the previous observed place serves as the starting point for calculating the next day; then the resulting current in direction and speed will be the average for the previous 24 hours.

In fact, both of these methods of determining the ship's position have their own errors, which are completely included in the magnitude of the determined current. The error in the astronomical position of the ship is currently estimated at 3 "meridian, or 3 nautical miles (5.6 km); the error in the calculable place is always greater. Thus, if the current obtained per day is only about 5-6 nautical miles(9-11 km), then this value cannot be attributed to the current, because it is within the limits of the errors in determining the positions of the ship, and such cases, when processing observations over currents, are considered as cases when there was no current at all.

Maps of ocean currents are based on tens of thousands of observations of this kind, and for most of the squares there are hundreds of cases of vessel observations of currents, and therefore random causes of inaccuracies in the definitions of currents, as well as random directions and speeds of currents, remain without influence on average conclusions.

In any case, cartographic processing of currents based on ship observations is much more difficult and complex than the same processing of other elements: temperature, salinity, etc.

The main causes of errors in determining the positions of a ship in the open ocean are as follows.

In the astronomical method, the main sources of error lie in the often vagueness of the natural (visible) horizon, above which the height of the luminary is taken, and inaccurate knowledge of the earth's refraction, which, with an unclear horizon, cannot be found from observations, and finally in an insufficient study of the sextant. Then "" chronometers, despite all their improvements, due to the accumulation of errors in the daily course, the change of which is affected by rolling on waves and shaking from wave impacts and shaking from the machine on steam ships, always give time from the original meridian, not exactly what is included entirely in the error of longitude.

In navigation mode major mistakes come from the following reasons: the ship never goes exactly on the intended course, because the helmsman always wags a little; ship by different reasons(wave, wind, unevenness in course) leaves the course line, and the helmsman tries to bring him to the course. In the ship's compass, although the influence of the ship's iron - deviation is excluded, nevertheless, a certain amount of compass deviation always remains, therefore, the course they are following is in fact different than the intended one. The swim distance is now determined much better than before, thanks to various mechanical lags that give a straight swim distance, and not the speed of the ship for different moments. But still, even with this method, there are errors in determining the swum distance.

Since latitudes in the sea are determined more precisely than longitudes, as a result of this, all ship definitions of currents in general exaggerate the magnitude of that component of currents that is directed to the east or west.

All these sources of error in determining ship positions at sea on ships of navies have the least effect on the accuracy of ship positions; on the ships of large shipping companies containing postal voyages, the errors are already somewhat larger, but on ordinary cargo ships these errors reach largest size. Meanwhile, according to the number of observations last genus courts is many times greater than the first two.

All of the above referred to the most common case of determining the current in the open ocean; in view of the shores, the same method of comparing the observed and countable places of the ship, while retaining its value, becomes incomparably more accurate, because instead of the astronomical method of determining the observed place, they use the method of determining it from observations of coastal objects, the position of which is on the map. Then the observed place of the ship does not depend on the errors of the chronometer and sextant, the inaccuracy of refraction, and so on. But this technique is only suitable for determining coastal currents.

Geography lesson in 7th grade e

Topic: "Ocean currents"

Target: reveal the reasons roundabout surface waters, give an idea of general scheme surface currents in the oceans.

Tasks:

To form an idea of ​​\u200b\u200bocean currents, the reason for their occurrence, the types of currents and their use.

reveal general patterns ocean currents

Continue learning to work with contour maps, identify patterns, read atlas maps.

Cultivate an aesthetic perception of geographical objects

Equipment: textbook, atlas, map of the oceans, physical map of the 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. Importance of ocean currents.

Lesson type: combined.

DURING THE CLASSES

Organizing time

Good morning, guys! Sit down in your seats, check the readiness for the lesson, whether 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, having discarded all the 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 areas of the earth. Let's remember what we talked about in the past and previous lessons.

1. For the board to perform an individual task will go

Draw a diagram of atmospheric circulation using colored crayons (Task card, blue, red and green chalk)

2.Individual test of our geographic simulator on the issues will perform on a laptop

3. And let's remember what a climate zone is?

Climatic zone -

What are the climatic zones? (main and transitional)

What prefix do we use to denote the transitional climatic zone (Sub)

How many main belts? (7)

What are the main climatic zones (equatorial, tropical, temperate, arctic, antarctic)

Show the main climatic zones on the map ...

How many transition belts? (6)

Name the transitional climatic zones (2 subequatorial, 2 subtropical, subarctic, subantarctic)

Show on the map the transition zones ...

What is the difference between main and transitional belts.

Do all zones have climatic regions (no)

Which climate zone does not have climate regions

Name and show them on the area map temperate zone Eurasia (moderate continental, continental, sharply continental, monsoonal)

4. Let's listen to what you wrote in your home mini-composition “I would like to live in …….belt, because…..

Let's see how I coped with the task ... test passed

Knowledge update

You and I remembered what we studied and it's time for us to turn to new material, but it will not be new for us at all. in the 6th grade we already got acquainted with the peculiarities of the nature of the Earth.

And today we will move from atmospheric processes to water processes.

And what is the name water shell Earth? (hydrosphere)

And this picture will become the symbol of our lesson . 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. For 101 days a brave navigator crossed over Pacific Ocean.

And in 1969, he undertook a new dangerous expedition to prove the possibility of crossing the Atlantic Ocean by African peoples.

He and six of his followers built a papyrus boat, called it "Ra". Their first trip failed. On the next year they once again took to the ocean in a papyrus boat, and this time reached their destination in 57 days.

Let's turn to the map: Thor Heyerdahl made a boat trip from the port of Safi (32 0 with. sh. and 9 0 h. e.) to the island of Barbados (13 0 with. sh. and 59 0 h. d.). Follow his route on a map of the oceans. What helped the traveler along the way?

A good way to get around is to move 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 notebooks, write down the date and the topic of our lesson.

What do you guys think, what are the questions we face in this topic?

What are ocean currents?

What are the currents?

How are they formed?

How do people use ocean currents?

To get answers to our questions, we need to turn to our main source of knowledge. What is it? 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 background prepared for us...

(REPORT ON THE HISTORY OF THE DISCOVERY OF OCEANIC CURRENTS)

What is the reason for the formation of ocean currents in the World Ocean?

VIDEO

What reason leads to the formation of currents (due to the influence of constant winds). What do we know about constant winds? (Assignment at the board)But there are several other reasons that affect the direction of currents:

1. Constant winds.2. Outlines of the continents.

3. Bottom relief
4 . 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 C. What is this current?( Warm)

And the Peruvian current off the coast South America has a temperature of +19 0 S, what is it? (Cold).

What is the contradiction? (+10 0 C - warm, + 19 0 C - cold)What is the question?

Which currents are called cold and which are warm?

Let's work and fill in the table that you have on your desk

Let's write down

Current name

Color on the map

Current water temperature

Ocean surface water temperature

Temperature Comparison

Type of flow

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 water in the ocean.….

Read the page in the textbook and compare, did we draw the right conclusion?

- warm current A current is a current whose water temperature is several degrees higher than the temperature of the surrounding water.

- cold flow It is a current, the temperature of which is several degrees lower than the surrounding water.

Find on the map and put on the c / c currents: Gulf Stream, Canary, Peruvian, Labrador, West 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, flow counterclockwise.)

Look closely at the map. What conclusions can be drawn by analyzing the patterns of currents in the northern and southern hemispheres?

Just the direction of currents clockwise and counterclockwise is influenced by the rotation of the Earth around its axis. To the north of the equator, the currents bend to the right, to the south of the equator to the left. This phenomenon is called the Coriolis effect, named after its creator. French mathematician Gaspard de Coriolis. This is a law of physics and you will study it in high school. Currents travel clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.

Fizminutka

Let's take a break from our studies and warm up. What phenomena can be found in the ocean? Waves, storm, hurricane, tsunami… Let's try to depict these phenomena… wave….higher… storm starts…. A hurricane… during a seaquake, a tsunami is formed… quieter, quieter…. We moor to the shore ... that is, at the desk. We warmed up .. Let's continue.

– Are all currents driven by wind?

If the water flow encounters an obstacle (land or uplift of the bottom topography), it divides, bending around the obstacle with different sides. The current 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 sewer 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 two waste currents are formed instead. Find examples on the map.(California and Alaska, East Australian and Intertrade, Kuroshio and Intertrade.)

Apply to contour maps two waste streams by thicker arrows.

From what current is formed ... current
- Find the current of the West Winds on the map of the oceans. What oceans does it cross?

(VIDEO ON THE CURRENT OF THE WESTERN WINDS)

Poem about the Course of the West Winds

Antarctica past Australia, America and Africa
Past all possible islands…
Everyone is sailing, my boats are sailing
Downstream of the West Winds.
I will draw on a worn map
This amazing route
In the blue of the vast expanse
Everyone is sailing, boats are sailing.

Speaking of ocean currents, it seems to me that it will be very useful to know the features of the current of our native sea.

What sea am I talking about? (Black)

Which ocean basin does it belong to (Atlantic)

Learn about the currents of the Black Sea will help us ...

Currents of the Black Sea

The main course of the Black Sea is the Main Black Sea Current. It is directed counterclockwise and forms two noticeable rings (“Knipovich glasses”, such a name is associated with the Russian hydrologist Nikolai Knipovich, who described this current). The flow is very changeable. In the coastal waters of the Black Sea, eddies of the opposite direction are formed - anticyclonic currents.

And who likes to swim in the sea in summer? Why?

Water procedures very useful, but know that the sea is fraught with danger .... You are welcome….

Secrets of the Black Sea

When swimming in the Black Sea, you should be aware of the existence of a local Black Sea current - “ traction». In the world, a similar phenomenon is called RIP.

Most often, this current is formed during a storm near sandy shores. The water running ashore does not return back evenly, but in jets along the channels formed in the sandy bottom.

It is dangerous to get into the jet of a draft: it can be carried away to the open sea. To get out of the drag, you need to swim not directly to the shore, but at an angle to reduce the resistance of receding water.

V. Stage of consolidation of knowledge

You and I are practically done with the material. Let's remember what we wanted to know...

Have we received answers ... But we know far from everything. You can add to your knowledge by completing homework Let's write it down in a diary.VI. Homework

1. Study &20., describe one of the currents according to the plan p.572.Creativeexerciseprepare a flow reportEl Niño

Verification test

1. What has the greatest effect on the formation of currents in the ocean

A) persistent winds

B) earthquakes

B) the pull of the moon

2. What are the currents

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 effects of ocean currents

A) on the formation of the climate

B) on the formation of the topography of the ocean floor

B) the rotation of the earth

5. What is the largest cold current

A) Gulf Stream

B) The course of the West winds

B) Peruvian Current

VII. Summing up results lesson a

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History of the discovery of surface currents

The first mentions of the existence of sea currents are found among ancient Greek scientists; Aristotle in his writings speaks of currents in the Kerch, Bosphorus and Dardanelles straits. And the Carthaginians had some idea of ​​the Sargasso Sea.

It is known that in the Middle Ages the Norwegians discovered sea ​​route from northern Europe, first to Iceland, and then to Greenland and North America. In these voyages, the Normans got acquainted with the sea currents. This is clear from the names that they gave to prominent places they met along the way, such as: Fr. Currents, Gulf of Currents, Cape Currents.

The Arabs sailed extensively in the Indian Ocean and established maritime communications with China, Mesopotamia and Egypt. They were familiar with the monsoon currents.

The Portuguese, when moving south along the coast of Africa, got acquainted with the Guinean 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. sh. and 40° W. e. He, by the deviation of the lot, lowered deep into the water, noticed that the ship was carrying the current to the SW. Subsequent voyages of Columbus 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 that runs along the coast of Honduras.

Currents are very importance for navigation, affecting the speed and direction of the vessel. Therefore, in navigation it is very important to be able to take them into account correctly (Fig. 18.6).

To select the best and safe ways when sailing near the coast and on the high seas, it is important to know the nature, direction and speed of sea currents.
When sailing by dead reckoning, sea currents can have a significant effect on its accuracy.

Sea currents - the movement of water masses in the sea or in the ocean from one place to another. The main causes of sea currents are wind, Atmosphere pressure, tidal phenomena.

Sea currents are divided into the following types

1. Wind and drift currents arise under the influence of wind due to the friction of moving air masses on the sea surface. Prolonged, or prevailing, winds cause the movement of not only the upper, but also more deep layers water and form drift currents.
Moreover, drift currents caused by trade winds (constant winds) are constant, and drift currents caused by monsoons (variable winds) change both direction and speed during the year. Temporary, short-lived winds cause wind currents that are of a variable nature.

2. Tidal currents are caused by changes in sea level due to tides. In the open sea, tidal currents constantly change their direction: in the northern hemisphere - clockwise, in the southern - counterclockwise. In the straits narrow bays and off the coast, the currents at high tide are directed in one direction, and at low tide - in the opposite direction.

3. Waste currents are caused by an increase in sea level in some of its areas as a result of inflow fresh water from rivers, large amounts of precipitation, etc.

4. Density currents arise due to uneven distribution of water density in the horizontal direction.

5. Compensatory currents arise in a particular area to make up for the loss of water caused by its runoff or surge.

Rice. 18.6. Currents of the oceans

Gulf Stream - the most powerful warm current of the World Ocean flows along the coast North America in the Atlantic Ocean, and then deviates from the coast and breaks up into a number of branches. The northern branch, or North Atlantic Current, runs to the northeast. The presence of the North Atlantic Warm Current explains the relatively mild winters on the coast. Northern Europe, as well as the existence of a number of ice-free ports.

In the Pacific Ocean, the north trade wind (equatorial) current begins off the coast Central America, crosses the Pacific Ocean at an average speed of about 1 knot, and Philippine Islands splits into several branches.
The main branch of the North Trade Wind Current runs along the Philippine Islands and follows to the northeast under the name Kuroshio, which is the second most powerful warm current of the World Ocean after the Gulf Stream; its speed is from 1 to 2 knots and even at times up to 3 knots.
Near southern tip islands of Kyushu, this current is divided into two branches, one of which - the Tsushima current is sent to Korea Strait.
The other, moving to the northeast, passes into the North Pacific Current, which crosses the ocean to the east. The cold Kuril Current (Oyashio) follows Kuroshio along the Kuril Ridge and meets it approximately at the latitude of the Sangar Strait.

The current of the westerly winds off the coast of South America is divided into two branches, one of which gives rise to the cold Peruvian current.

In the Indian Ocean, the southern trade wind (equatorial) current near the island of Madagascar is divided into two branches. One branch turns to the south and forms the Mozambique current, the speed of which is from 2 to 4 knots.
At the southern tip of Africa, the Mozambique Current gives rise to the warm, powerful and stable Needle Current, average speed which is more than 2 knots, and the maximum is about 4.5 knots.

In the Arctic Ocean, the bulk of the surface layer of water moves clockwise from east to west.