UPSC NCERT Notes – Geography – Waves, Ocean Currents, and Tides

Studying the dynamic forces shaping Earth’s oceans is an essential endeavor for understanding the intricate interplay of natural systems on our planet. Within the vast expanse of oceanic realms, waves, ocean currents, and tides emerge as pivotal phenomena, orchestrating the movement of water masses across global scales. Delving into the nuances of these elements not only unveils the profound influence they exert on marine ecosystems, climate patterns, and coastal landscapes but also underscores their significance in human activities such as navigation, fishing, and coastal engineering. In this compilation of UPSC NCERT notes on geography, we embark on a journey to unravel the mysteries of waves, ocean currents, and tides, deciphering their mechanisms, impacts, and interconnectedness within Earth’s dynamic geosphere.

Waves

• Waves are essentially oscillatory movements resulting in the fluctuation of the water surface. These movements represent horizontal shifts in the ocean water. It’s important to note that waves are manifestations of energy, not the water itself, traversing the ocean surface. This energy is primarily provided by the wind.
• In a wave, each water particle undergoes circular motion. The wave consists of two main components: the elevated portion referred to as the crest and the lower point known as the trough.
• Waves are characterized by their wavelength, which is the distance between two consecutive crests or troughs. Additionally, the wave period indicates the time it takes for a wave to travel its wavelength, and wave frequency signifies the number of wave crests passing a fixed location within a specific timeframe.
• As waves travel, they traverse through the water, causing circular motions rather than significant water displacement. Various factors contribute to the origin of waves, including atmospheric circulation and winds, landslides in coastal regions, and tectonic events in the seafloor such as faulting and subduction.
  • Occurrences of oceanic earthquakes in the oceanbed
  • Eruptions of volcanoes on the ocean floor
  • Gravitational forces exerted by the Moon and the Sun
  • Cyclones

Ocean Currents

• Ocean currents, akin to the flow of rivers in oceans, refer to the movement of a quantity of ocean water over a considerable distance in a specific direction.
• Currents are influenced by various forces, carrying both heat and density across latitudes in vertical and horizontal directions. In the Northern Hemisphere, ocean currents flow clockwise, while in the Southern Hemisphere, they move counterclockwise. The reverse flow of the current beneath the surface is termed an undercurrent.

Gyre, Drift, and Stream

• A large system of rotating ocean currents, particularly influenced by significant wind movements, is termed a Gyre and is caused by the Coriolis force. 
• When ocean water moves forward under prevailing winds, it is called Drift, with examples like the North Atlantic Drift. 
• The term ‘drift’ is also used to denote the speed of an ocean current, measured in knots. When a substantial mass of ocean water moves in a defined path, similar to a river on a continent, it is referred to as a Stream, typically possessing greater speed than drifts (e.g., Gulf Stream in the North Atlantic Ocean).

Factors Influencing the Origin of Currents

• Ocean currents are influenced by both internal and external factors. Wind, density differences in water masses, and temperature and salinity variations are external factors, while gravity, earthquakes, and storms are other external events that contribute to ocean currents.

Internal Ocean Factors

• Temperature, salinity, and density of ocean water are internal factors influencing ocean currents.
  • Variation in Temperature The Sun’s rays fall vertically on the Equator, leading to increased temperature in ocean water. As the density decreases, equatorial water currents are initiated.
  • Variation in Salinity Salinity differences cause more saline water to settle at the bottom, creating movement as less saline water moves towards more saline areas.
  • Variation in Density Ocean water density fluctuates due to temperature, salinity, pressure, and ice melting in high latitudinal regions. This density variability results in ocean water movements.
• Circulation, known as Thermohaline circulation, occurs due to differences in density based on temperature and salinity. In polar regions with lower temperatures, denser ocean water sinks and moves towards less dense middle and lower latitudes or equatorial regions.
• Ocean water rises in warm regions, pushing existing less dense warm water towards the poles.

External Ocean Factors

• Ocean water experiences various influences, including air pressure, winds, precipitation, and evaporation.

Air Pressure and Winds

• In ocean water, high air pressure corresponds to low seawater levels, while low air pressure leads to high seawater levels. 
• This pressure difference prompts water from areas of low air pressure to move towards high air pressure, generating ocean currents. Prevailing and monsoon winds also contribute to the creation of ocean currents. Winds, as they move over the sea, induce water movement due to friction, thus generating ocean currents.
• Changes in wind direction result in alterations to the current direction.

Precipitation and Evaporation

• The processes of precipitation and evaporation impact salinity and density, influencing ocean currents.
• Coastline features, shape, and bottom relief also play a role in influencing ocean currents, creating secondary waves rather than being direct causes.

Types of Ocean Currents

Ocean currents are categorized based on temperature into warm and cold currents.

Warm Currents

• These currents move from low latitudes (equatorial regions) to high latitudes (poles) and bring warm waters to colder regions. Their water temperature exceeds that of the waters they traverse, raising the temperature of the areas they move towards. Typically observed on the East coast of continents in lower and middle latitudes, they are also found on the West coast in higher latitudes in the Northern hemisphere (e.g., Alaska and Norwegian Currents).

Cold Currents

• Originating from polar regions and flowing towards the Equator, these currents have lower surface temperatures. 
• Their water temperature is lower than the surrounding waters, reducing the temperature of the areas they traverse. They bring cold waters into warmer regions. 
• Usually found on the West coast of continents in low and middle latitudes, they are also present on the East coast in higher latitudes in the Northern hemisphere (e.g., Labrador, East Greenland, and Oyashio Currents).

Pacific Ocean Currents

North Equatorial Current

• This warm current flows from East to West across the ocean, increasing in volume as it moves towards the West. Beginning on the West coast of Central America, it reaches the Philippine Islands, always flowing North of the Equator.

Kuroshio Current

• The North Equatorial Current continues North along the Philippine Islands, and coasts of Taiwan and Japan, forming the Kuroshio Current. It is a warm current and is considered the extension of the North Equatorial Current.

North Pacific Drift

• Starting from the Southeast coast of Japan, the Kuroshio Current changes direction under the influence of prevailing Westerly winds, flowing from West to East. This warm current, known as the North Pacific Drift, bifurcates into two branches.

Alaska Current

• The Northern branch of the North Pacific Drift flows anti-clockwise along the coast of British Columbia and Alaska, named the Alaska Current.
• The temperature of this current is comparatively warmer than the surrounding water in its vicinity.

South Equatorial and East Australian Current

• The East Australian current is a warm, southward-flowing, western boundary current formed by the South Equatorial current as it traverses the Coral Sea and reaches the eastern coast of Australia. 
• Similar to the Northern Hemisphere pattern, the South Equatorial current moves from east to west and then turns southward, becoming the East Australian current.

South Pacific Current

• In the vicinity of Tasmania, the East Australian current is influenced by westerly winds and changes its direction to flow from west to east. This segment is known as the South Pacific current. The South Pacific subtropical gyre primarily governs the South Pacific current system, including the East Australian current and the Peru current.

Counter-Equatorial Current

• A current flows parallel to the North and South equatorial currents but in the opposite direction from west to east. This is termed the counter-equatorial current. 
• The genesis of this current is explained by a disruption in the water balance due to the accumulation of water in the western sector caused by the movement of the two equatorial currents. 
• The counter-equatorial currents flowing from west to east help maintain the water balance.

Californian Current

• The southern branch of this current functions as a cold current along the west coast of the USA and is referred to as the Californian current. 
• The Californian current joins the North Equatorial current to complete the circuit. It plays a role in the formation of the Mojave and Sonoran deserts.

Oyashio and Okhotsk

• In the Pacific, there are two cold currents: the Northern current flows past the Kamchatka Peninsula to merge with the warmer waters of the Kuroshio, while the Okhotsk current flows past Sakhalin and merges with the Oyashio current off the Hokkaido Islands.

Peru Cold Current

• The South Pacific Current reaches the south coast and begins flowing in a south-to-north direction parallel to the Peruvian coast, eventually merging with the South Equatorial Current.
• This segment is also known as Humboldt’s current and is a cold current. This current is a contributing factor to the formation of the Atacama Desert.

West Wind Drift

•  It is cold strong ocean current. It flows from West to East under the influence of the Westerlies between Tasmania and South American coast in the zone of 40°-50°S latitudes.
• This current becomes much stronger because of immense volume of water mass and high velocity winds called as roaring forties and thus, the current flows with great velocity

El-Nino and La-Nina Phenomena

• El-Nino is a warm ocean current that flows from north to south between 3°S and 36°S latitudes, approximately 180 km away from the Peruvian coastal site. Both El-Nino and La-Nina are seasonal occurrences linked to changes in Pacific Ocean temperatures.
• The origin of El-Nino is associated with increased temperatures in the Eastern Pacific Ocean. This warm water current leads to above-normal rainfall on the coast of Peru, resulting in the sea’s coastal area turning green. El-Nino negatively impacts the marine ecosystem, causing the death of fishes, plankton, and other marine animals.
• El-Nino causes excessive rainfall in the East Pacific Ocean region and triggers drought conditions in the Western Pacific Ocean region. It also adversely affects the monsoon in South-East Asia, leading to drought conditions in countries like Indonesia, India, and Bangladesh.
• Following the end of El-Nino in the Eastern Pacific Ocean, La-Nina emerges in the Western Pacific Ocean, creating the opposite scenario. La-Nina restores normal weather conditions.
• El-Nino is symbolically referred to as “baby Jesus,” and La-Nina is likened to his younger sister.

Currents of the Atlantic Ocean

The currents of the Atlantic Ocean include the following:

North Equatorial Current

• Typically forming between the Equator and 10° N latitude, the North Equatorial Current results from the upwelling of cold water near the West coast of Africa. This warm current is pushed westward by the cold Canary current and then turns southward after crossing the ridge. It bifurcates into two branches: the Antilles Current and the Caribbean Current.
• Antilles Current: Diverting northward, this current flows east of the West Indies islands, contributing to the formation of the Sargasso Sea eddy.
• Caribbean Current: The second branch enters the Gulf of Mexico and becomes the Gulf Stream.

Florida Current

• A rise in water level in the Mexican Gulf leads to the flow of a current through the Strait of Florida, joined by the Antilles current from the south, forming the Gulf Stream beyond Cape Hatteras. 
• The Gulf Stream is wide, warm, and separated from the Sargasso Sea on its right (east) and relatively cold water near the coast on its left.

North Atlantic Current

• Turning east under the influence of the westerly wind from the Grand Banks, the Gulf Stream becomes the North Atlantic Current. It breaks into two branches upon reaching the eastern part of the ocean.

South Equatorial Current

• In the South Atlantic Ocean, the South Equatorial Current splits into two branches near Cape de Sao Roque (Brazil). The northern branch joins the North Equatorial Current, while the southern branch turns southward and flows along the South American coast as the Brazil Current.

Brazil Current

• The Brazil Current shifts eastward at approximately latitude 35°S, joining the West Wind Drift flowing from west to east.

• Along the western coast of South Africa, the cold Benguela current flows and merges with the South Equatorial Current to complete the circuit.

Counter-Equatorial Current

• Flowing from west to east between the strong westward currents of the North and South Equatorial currents, this current is less developed in the west due to the influence of trade winds.

Canary Current

• The southerly branch flows between Spain and the Azores as the cold Canary current. Eventually, it joins the North Equatorial Current, completing the circuit in the North Atlantic. The Sargasso Sea, located within this circuit, is rich in seaweed.

Sargasso Sea

• In the North Atlantic Ocean, an anticyclone circulation is formed by the North Equatorial Gulf Stream and the Canary Current, resulting in calm and motionless water. The Sargasso Sea is characterized by an abundance of Sargassum grass and holds the highest salinity in the Atlantic Ocean at 37%. This phenomenon is referred to as the Oceanic desert.

Greenland Current and Labrador Current

• Two cold currents, the East Greenland current and the Labrador current, flow from the Arctic Ocean into the Atlantic Ocean.
• The Labrador current flows along part of the east coast of Canada and meets the warm Gulf Stream. The convergence of these hot and cold currents produces famous fogs around Newfoundland.

Falkland Current

• The Falkland current, another cold current, flows along the southeastern coast of South America from south to north. 
• It is the eastward continuation of the Brazil current and is generated due to the deflective force of the Earth’s rotation.

South Atlantic Drift

• It is the Eastward continuation of the Brazil current.
• This current is generated due to the deflection of the Brazil warm current Eastward at 40° S latitude due to the deflective force of the rotation of the Earth. It thus, flows Eastward under the influence of the Westerlies.
• This current is also known as the Westerlies drift or the Antaretic drift.

Benguela Current

• A cold current flowing from south to north along the western coast of South Africa, the Benguela Current is responsible for the South Atlantic drift turning and contributing to the formation of the Kalahari Desert.

Currents of the Indian Ocean

• The Indian Ocean, being landlocked in the north, exhibits a unique current circulation pattern. The currents in the northern portion of the Indian Ocean change direction seasonally, responding to the monsoons. The influence of winds is more pronounced in the Indian Ocean.

South Equatorial Current

• In the northern section of the Indian Ocean, there is a reversal of currents between winter and summer. In winter, the North Equatorial Current and the South Equatorial Current flow from east to west.
• A counter-equatorial current flows from west to east between the two equatorial currents. The southern part of the Indian Ocean experiences less marked seasonal changes, and the general circulation is anti-clockwise like that of other southern oceans.

Monsoon Current

• During the North-East monsoons, water along the Bay of Bengal coast circulates in an anti-clockwise direction. Similarly, along the coasts bordering the Arabian Sea, an anti-clockwise circulation known as the monsoon current develops.
• In summer, a robust west-to-east current prevails, completely overshadowing the North Equatorial Current during this season. This is attributed to the strong South-West monsoon and the absence of the North-East trades. There is no counter-equatorial current during this time, resulting in a clockwise circulation of water in the northern part of the ocean.

Mozambique Current

• The current flowing through the Mozambique Channel is referred to as the Warm Mozambique Current.
• Further south, it combines with another branch of the South Equatorial Current flowing past Madagascar Island. The merged flow is then known as the Agulhas Current, maintaining its warm characteristics until it merges with the West Wind Drift.

Agulhas Current

• After the confluence of these two streams, it is recognized as the Agulhas current. It retains its warm nature until it merges with the West Wind Drift.

West Australian Current

• The West Wind Drift, traversing the ocean in higher latitudes from west to east, reaches the southern tip of the West coast of Australia. 
• One of its branches, known as the West Australian current, turns northward along the West coast of Australia, contributing to the South Equatorial Current.

Effects of Ocean Currents

Effects of ocean currents are as follows.

Effect on Heat Balance

• Currents influence the climatic conditions of the regions in which they flow. The warm Equatorial currents raise the temperature of the region in which they flow. Similarly, the cold currents lower the temperature of the places where they flow.
• For example, British Isles would have been extremely cold without the warm North Atlantic drift. The hot climate of Peru is cooled by the cold Peru current.

Effect on Rainfall

• The winds blowing over warm currents pick up and carry moisture and bring rainfall like the North Atlantic drift bring rainfall in some areas located along the Western coasts of Europe.
• On the contrary, cold currents do not bring rainfall and make the region cooler and drier. The Kalahari desert hardly experiences rainfall due to the cold Benguela current.
• Sometimes, the convergence of a warm and a cold current can lead to violent storms. Hurricanes off the coast of the USA, for instance, often follow the line where the Gulf Stream merges with the Labrador current.

Stimulation to Fishing

• The interaction of warm and cold currents results in the accumulation of plankton, creating ideal conditions for abundant fish populations in those areas.

Effect on Trade and Navigation

• Currents offer favorable sailing conditions if ships align with their directions. Numerous warm currents prevent European ports from freezing during winters, facilitating year-round trade. 
• However, the meeting of warm and cold currents can lead to fog, posing dangers to ships and causing historical shipwrecks due to reduced visibility.

Tides

• Tides occur due to periodic changes in sea level, influenced by the gravitational forces of the Moon and Sun.
• The study of tides is intricate, given their spatial and temporal variations in frequency, magnitude, and height.

Causes Responsible for the Occurrence of Tides

• The primary causes of tides are the gravitational pull of the Moon and, to a lesser extent, the Sun, along with the counterbalancing force of centrifugal force. Tidal bulges are created due to the difference between the Moon’s gravitational attraction and the centrifugal force, resulting in two bulges—one facing the Moon and the other away.
• The horizontal forces on the Earth’s surface play a crucial role in generating tidal bulges. Wide continental shelves experience higher tidal bulges, while mid-oceanic islands witness lower ones. The shape of bays and estuaries can amplify tidal intensity, and when channeled between islands, they are referred to as tidal currents.

Types of Tides

• Different types of tides occur due to varying positions of the Sun and Moon relative to the Earth. High tides include the direct tide (facing the Moon) and opposite tide (opposite side of the Earth), occurring simultaneously.

High Tides 

• The side of the Earth facing the Moon will have tidal bulge called the direct tide. Similarly, on the opposite side of the planet, the ocean will also be bulging. This is called the opposite tide. 
• It happens because the inertial force of the Earth exceeds the gravitational force of the Moon at this location. Therefore, high tides occur simultaneously on 

Low Tides

• Tides manifest as the receding waters between high tide events, with variations in low tide levels observed in different locations. In some places, low tide might only be a few feet, while in others, the ocean can withdraw much farther.
• High and low tides occur twice each in a 24-hour day, but due to the Moon rising 50 minutes later daily, the timing of tide cycles differs by the same 50 minutes each day.

Spring Tides

• The phases of the Moon influence tides, with full or new Moon phases resulting in the highest high tides and lower-than-usual low tides. These spring tides occur during syzygy, when the Sun, Moon, and Earth align in a straight line, causing increased gravitational influence from the Sun, leading to more pronounced ocean bulging.

Neap Tides

• During the Moon’s quarter phases, the Sun’s gravitational pull opposes the Moon’s, resulting in the lowest high tide and the highest low tide. This phenomenon, known as a neap tide, represents the least extreme difference between high and low tides.

Periodic Tides

• Apogean tides and perihelion tides occur when the Moon is at apogee (farthest) or perigee (nearest) to the Earth. These are monthly tides, while aphelion and perihelion lead to yearly tidal variations. Equinoctial spring tides occur every six months.

Tidal Bore

• A tidal bore is a phenomenon where the incoming tide’s leading edge forms waves that travel up a river or narrow bay against the current’s direction.

Importance of Tides

• Tides influence marine ecosystems, particularly the intertidal zone between high and low tide, affecting the types of plants and animals that thrive in this dynamic environment. 
• High tides aid navigation, raising water levels near shores for easier harbor access. Tides also contribute to making rivers navigable for ocean-going vessels. 
• Additionally, high tides facilitate fishing by bringing more fish closer to the shore, ensuring plentiful catches. Tides play a role in desilting sediments and removing polluted water from river estuaries. Furthermore, tides are harnessed for generating electrical power in various countries, including Canada, France, Russia, and China.

Prelims Facts

• Which factors influence the Ocean currents? In an El-Nino year low air pressure develops over large coastal region of which ocean -Pacific Ocean (MPSC (Pr) 2012
• Of high tide, low tide What are the causes the ocean formation -Gravitation, Centripetal force (Pre) Centrifugal force (IAS (Pre) 2015,
• Rotation of the Earth, air pressure, wind and density of ocean water [LAS (Pre) 2012
• Which factor is responsible for the change in the regular direction of the Ocean currents in the Indian Ocean / Indian Ocean has monsoon drift (IAS (Pre) 1997)
• In which ocean Agulhas current flows? Indian Ocean (RAS/RTS (Prr) 1999)
• Which country benefitting the most of out of the North Atlantic Drift is -Norway IRAS/RTS (Pre) 1999)
• An only cold current of South Atlantic Ocean is the -Benguela Current [UPPSC (Pre) 2005)
• Agulhas and Mozambique currents belong to which ocean? -Indian Ocean (UPPSC (Mains) 2014
• The Peruvian current or Humboldt currant is related to -South-East Pacific Ocean (UPPSC (Pre) 1995)
• Gulf stream is powerful Warm Current in the North Atlantic Ocean (BPSC (Pre) 2000)
• What is the reason for the Eastward flow of the equatorial counter-current -The Earth’s rotation on its axis (IAS (Pre) 2015]
• In the absence of Cold Labrador current what will happen -There will be no North-West Atlantic fishing grounds (BPSC (Pre) 2001
• The cause of producing indirect light tide is Centrifugal force of the Earth (RAS (Pre) 1999
• Tides in the sea are caused by -Effect of Sun (JPSC (Pre) 2012
• Tided occur in ocean and seas due to which factor’s Gravitational force of Sun, Moon and centrif force of Earth [LAS (Pre) 2015
• Spring tide occurs A straight line (UPPSC (Pre) 1999
• The high tide in the ocean is caused by Moon [BPSC (Pre) 2014
• What explains the Eastward flow of the equatorial counter-current? Convergence of the to equatorial current [IAS (Pre) 2015
• What is the nature of East Australian current? – Warm Ocean current [UPPSC (Pre) 2009
• The Cold current flowing in Indian Ocean is – Falkland current [MPPSC (Pre) 2016

UPSC NCERT Practice Questions

1. Consider the following statements. UPSSC (Pre) 2002

1. Ocean currents are the slow surface movement of water in the ocean.

2. Ocean currents assist in maintaining the Earth’s heat balance.

3. Ocean currents are set in motion primarily by prevailing winds.

4. Ocean currents are affected by the configuration of the ocean.

Which of these statement(s) is/are correct?

(a) 1 and 2

(b) 2, 3 and 4

(c) 1, 3 and 4

(d) All of the above

2. Which of the following factors influence ocean currents?

1. Rotation of the Earth 

2. Air pressure and wind

3. Ocean water density 

4. Revolution of the Earth

Codes

(a) 1 and 2 

(b) 1, 2 and 3

(c) 1 and 4

(d) 2, 3 and 4

3. Consider the following statements. 

Statement 1 The ocean currents flowing from the Equator to the North pole and from the pole to the Equator in the Northern hemisphere by its deflected to the right.

Statement 2 This is due to the rotation of the Earth on its axis from West to East.

Codes

(a) Both the statements are true and statement 2 is the correct explanation of statement 1.

(b) Both the statements are true, but statement 2 is not the correct explanation of statement 1.

(c) Statement 1 is true, but statement 2 is false. 

(d) Statement 1 in false, but statement 2 is true.

4. Match Last I with List II and select the correct answer by using the codes given below the lists.

List I (Ocean Currents)	List II (Coasts)
A. Humboldt	1. Namibia Angola
B. North Atlantic Drift	2. Chile Peru
C. Benguela	3. Mozambique Madagascar
D. Agulhas	4. United Kingdom Norway

Codes

(a) 2 1 4 3 

(b) 2 4 1 3 

(c) 3 4 1 2                                         

(d) 3 1 4 2

5. Regular and continuous cycle of ocean currents like Atlantic and Pacific oceans does not run in the Indian ocean, because MPSC (Mains) 2015

(a) region beyond 25° N latitude is occupied by continents.

(b) direction of the ocean current is deflected by conventional winds.

(c) the direction of monsoon of Indian ocean changes in various seasons. 

(d) All of the above

6. Match List I with List II and select the correct answer by using the codes given below the lists. JPSC (Pre) 2013

List I	List II
A. Gulf stream	1. Pacific ocean
B. West Wind Drift	2. A slow Eastward movement of water over the zone of Westerly wind
C. Peru Current	3. Indian ocean
D. West Australian Current	4. Warm current

Codes

 (a) 4 2 1 3   

(b) 1 3 4 2                                      

(c) 4 3 1 2                                         

(d) 1 2 4 3

7. The current produced by upwelling of cold water off the coast of Chile and Peru is known as

(a) El-Nino

(b) Humboldt current

(c) Agulhas current

(d) Canary current

8. Which one of the following is a cold ocean current?

(a) Brazilian current

(b) Gulf stream

(c) North Equatorial current

(d) California current

9. Consider the following statements Statement. 

Statement 1 The Kuroshio is a warm North flowing ocean current on the West side of the North Pacific ocean. 

Statement 2 Presence of a number of volcanoes at the bottom of the sea of Japan is responsible for the Kuroshio becoming warm.

Codes

(a) Both the statements are true and statement 2 is the correct explanation of statement 1

(b) Both the statements are true, but statement 2 is not the correct explanation of statement 1.

(c) Statement 1 is true, but statement 2 is false 

(d) Statement 1 is false, but statement 2 is true.

10. How is La-Nina different from El-Nino? UPPSC Pre 2011, MPSC (Mains) 2013

1. La-Nina is characterised by unusually cold ocean temperature in the Equatorial Indian ocean. Whereas, El-Nino is characterised by unusually warm ocean temperature in the Equatorial Pacific ocean. 

2. El-Nino has an adverse effect on South-West monsoon on India, but La Nina has no effect on

monsoon climate. 

Which of the statement(s) given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) neither 1 nor 2

11 . For short term climatic predictions, which one of the following events, detected in the last decade, is associated with occasional weak monsoon rains in the Indian subcontinent? IAS (Pre) 2002

(a) La-Nina

(b) Movement of Jet streams

(c) El-Nino and Southern oscillations

(d) Greenhouse effect on a global level

12. The Kuroshio is a North flowing ocean current on the West side on the North Pacific ocean. Which one among the following statements regarding this is not correct?

(a) It is similar to the Gulf stream in the North Atlantic ocean 

(b) It transports warm, tropical water Northward towards the polar region.

(c) The warm water of the Kuroshio current sustains the coral reefs of Japan.

(d) It begins off the coast of Japan and flows Northward..

13. A new type of El-Nino called ‘El-Nino Modoki’ appeared in the news. In this context, consider the following statements. UPPSC (Pre) 2020

1. Normal El-Nino forms in the Central Pacific ocean, whereas El-Nino Modoki forms in Eastern Pacific ocean.

2. Normal El-Nino results in diminished hurricanes in the Atlantic ocean but El-Nino Modoki results in a greater number of hurricanes with greater frequency. 

Which of the statement(s) given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

14. Consider the following statements. UPPSC (Pre) 2017

1. La-Nina means a little girl.

2. During the time of La-Nina cold water in the ocean rises to the surface. 

3. La Nina strengthens the Indian monsoon.

4. During the time of El-Nino, trade winds weaken and warm water moves East in the ocean.

Which of the statement(s) given above is/are correct?

(a) 1 and 2

(b) 1, 2 and 3

(c) 2 and 3

(d) All of the above

15. Which of the following is not a resultant of the El-Nino effect?

(a) Distortion of equatorial atmospheric circulation.

(b) Flow of the South-East trade winds towards the Indian ocean.

(c) Irregularities in the evaporation of sea water.

(d) Reduction in the amount of planktons, which reduces the number of fish in the sea.

16. What explains the Eastward flow of the equatorial counter current? IAS (Pre) 2015

(a) The Earth’s rotation on its axis.

(b) Convergence of the two Equatorial currents.

(c) Difference in salinity of water.

(d) Occurrence of the belt of calm near the Equator.

17. Which of the following oceanic current does no flow in North Atlantic ocean?

(a) Gulf stream

(b) Benguela

(c) Norwegian

(d) Florida

18. The Gulf stream is a poleward flowing current n following the Atlantic ocean. Which one of the statements with regard to this is not correct?

(a) It is similar to the Kuroshio current in the Noth It transports warm, tropical water towards Pacific ocean.

(b) It transports warm, tropical water towards polar region.

(c) This current is a major factor in weather along the East coast of the USA.

(d) The warm water of the Gulf stream sustains the coral reefs of West Pacific coast.

19. Which among the following statement(s) about the North Atlantic drift is/are correct?

1. It keeps the West coast of Northern Europe ice free.

2. It is responsible for the warm air mass, which interacts with the cold air mass from the polar

region and causes rainfall in Western Europe,

3. It meets the Labrador current near Vancouver island and causes dense fog.

Select the correct answer by using the codes given below.

(a) 1, 2 and 3

(b) 1 and 2

(c) Only 2

(d) 1 and 3

20. In the absence of cold Labrador current, which one among the following would happen? BPSC (Pre) 2001

(a) There will be no North-East Atlantic fishing grounds. 

(b) There will be no North-West Atlantic fishing grounds.

(c) There will be no fishing ground in the North Atlantic ocean.

(d) Semi-arid condition of the Atlantic coast of the USA and Canada would prevail.

Know Right Answer

1. (b)

2. (b)

3. (a)

4. (b)

5. (d)

6. (a)

7. (b)

8. (d)

9. (c)

10. (d)

11. (c)

12. (d)

13. (6)

14. (d)

15. (b)

16. (a)

17. (b)

18. (d)

19. (b)

20. (b)

Frequently Asked Questions (FAQs)

1. What’s the difference between a wave and a current?

• Waves: Imagine moving your hand up and down in water. The ripples you create are waves. They move energy across the surface, but the water itself doesn’t travel far. Think of them as “dancing in place.”
• Currents: These are like rivers in the ocean! They’re the sustained flow of water in a specific direction, often driven by wind, temperature differences, or even the force of the Earth’s rotation.

2. What causes tides, and how high can they get?

• Tides: The ocean bulges in and out due to the combined gravitational pull of the Moon and, to a lesser extent, the Sun. As Earth rotates, these bulges move around, causing high and low tides on different coasts.
• Height: Tide heights vary based on coastline shape, the Moon’s phase, and alignment with the Sun. Some places experience tiny changes, while others, like the Bay of Fundy, see dramatic swings of over 16 meters!

3. Do waves and currents affect each other?

• Absolutely! Wind-driven waves can create surface currents, and the shape of the coastline can funnel currents, making waves larger. In shallow areas, strong currents can break waves, creating choppy conditions.
• Bonus: Tides create powerful tidal currents near coasts, which can be dangerous for swimmers and boaters. Understanding these interactions is crucial for coastal communities.

Bonus FAQ: What are the biggest waves in the world?

• Monster waves, also known as rogue waves, can tower over 30 meters! These unpredictable giants arise from the interaction of multiple wave systems and can occur even in calm weather. Learning about and respecting the power of the ocean is essential for anyone venturing near the water.

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