Ocean Salinity

Ocean salinity is the element that increases the weight of ocean water/ocean load, measured in grams per thousand its symbol is ‰. (in quantity) in the Challenger expedition (1884) in which a scholar, Deidmer, said that 47 types of Salien were available.
It is as follows:

1) Sodium Chloride (NaCl) (27% ) (77.8‰) is the highest amount in the ocean.
2) Magnesium Chloride -(3.80%) (10.9‰)
3) Magnesium Sulphate – (1.65%) (4.7‰)
4) Calcium Sulphate – (1.26%) (3.6‰)
5) Potassium Sulphate- (0.86%) (2.5‰)
6) Calcium Carbonate – (0.12%) (0.3‰)

Ocean Salinity

Ocean salinity (source)

There are THREE types of sources

  1. Ocean of salinity
  2. Land
  3. Volcanic crust/Ash

Above are the sources of ocean salinity, among them is the first ocean crust which increases salinity due to mixing with water. Second is land (terrigenous) in which (gravel, sand, silt, and mud,) all mixed with water. And third, ash and gases from the volcano are also mixed. All these are called sources of ocean salinity.


  • Ocean salinity is low near 0°.
  • And near high latitudes i.e. (70°) latitude there is also low salinity.
  • Highest salinity occurs near 20°, 40°, 60°
  • (Van Lake has high salinity, it is an inland lake)

1. Temperature:

  • The temperature is higher near the line of Cancer and Capricorn and there is more salinity.

2. Rainfall:

  • Equator has a higher temperature, so evaporation occurs and rainfall occurs, so salinity is less.

3. Fresh water:

– The salinity is comparatively less in the sea where more rivers meet.

4. Wind and air pressure:

  • Air always flows from high pressure to low pressure,


Salt.                                                   Salt.

(H.p high pressure)

(L.p low pressure)

  • Can carry salt through air to places with less salt. It increases decency.
  • Low salinity occurs on the coast of California, because the air moving there takes salt/salinity with it and goes to low pressure, so salinity is low there.

5. Ocean waves:

There are different types of waves in the ocean.

  • Due to the wave of air in the North Atlantic Ocean, the salinity increases in the North Sea and Norwegian Sea.

Ocean Salinity Distribution


  • Isohaline = line of equal salinity
  • Salinity is also found in the North Hemisphere and in the South Hemisphere.
  • It can be seen in 20°- 30° latitude in North
  • And in the southern hemisphere it is seen in latitudes between 20° – 30° because,
  • The amount of land is more in the North and the amount of land is less in the South Hemisphere

Horizontal Distribution has two parts

  1. Vertical Distribution
  2. Regional Distribution
Vertical Distribution:
  • Salinity decreases from -0° as you move towards Polar area. And it is not found much on Equator.
  • It is less on Equator because the rainfall is more.
  • And it is less in polar area because there is less evaporation.
  • 0° Near Equator = 34‰ salinity
  • North hemisphere= 20°-40°N high salinity (36‰) and 40° goes to 31‰.
  • In the south hemisphere, high salinity is found between 10°-30°s, and as it goes to 40°, the salinity becomes 33‰.
  • 34‰ average salinity of north hemisphere, and 35‰ of south hemisphere.

Salinity is divided into 4 zones (on latitude base)

  1. Equator : low salinity zone.
  2. 20°-40° : high salinity.
  3. Temperate region: low salinity.
  4. Polar Area: lowest salinity.
Regional distribution:
  • Jenkins sir first presented Regional wise distribution of salinity.
  • Jenksin sir said ocean, Pacific Ocean, Atlantic Ocean, Indian Ocean.
  • Jenksin sir said 3 important regions in which number one is Pacific, number two is Atlantic Ocean and number three is Indian ocean.

Distribution of Pacific Ocean

  • The salinity is 34‰ at Equator of Pacific Ocean.
  • At -20°-40° N salinity is 35‰.
  • And till we go to polar area it is 31‰.
  • The ocean floor almost covered with a blanket of sediments.

Classification of Oceanic Deposits

Classification is done on the basis of 2 types

  1. Source
  2. Location


Source have THREE types

  1. Terrigenous
  2. Volcanic Eruption
  3. Biotic Deposit
  • Terrigenous means elements that move from land to ocean.
  • Terrigenous classification is based on size.

It have FIVE types

  1. Gravel
  2. Sand
  3. Silt
  4. Clay
  5. Mud

There are 4 types of Gravel. They are as follows (Gravel is deposited near the continental shelf, and is formed by rivers/flows with river water.)

a) Boulder: A particle of 256mm or larger.

b) Cobble: A particle of 64-256mm diameter.

c) Pobble: 4-64mm diameter is a particle.

d) Gravel: 2-3 mm diameter is a particle.


Sand has a diameter of 1-1/6 mm and this also has 5 types

a. Very coarse sand – about 1mm

b. Coarse sand – its diameter is 0.5 mm.

c. Medium sand- 0.25mm

d. Fine sand- 0.125mm

e. Very fine sand – 1/6mm.

  • Sand is made from pieces of gravel. Sand is formed next to the continental shelf i.e. on the continental slope.
  •  1/7 diameter – 1/256mm diameter.
  • It is produced by rivers or waves.
  • They extend to the continental slope because,
  • Its depth is 100-1000 fathoms.
  • It is formed in elements between surface and ocean
  • Its 1/892mm diameter
  • Classification of mud is done in 3 types
  • a) blue mud. b) Red mud. 3) Green mud.

a) Blue Mud– Blue mud contains high amount of iron sulphide.

– It has biotic component.

– Iron sulfide made of biological elements

– These muds are located near the continental shelf.

– This mud contains 35% lime.

– Most of the blue mud settles in the Atlantic Ocean.

b) Red Mud– Iron oxide and iron-rich rocks will be eroded and then transported and then deposited and accumulates in the sea.

– It contains calcium carbonate almost 32%

– This mud builds up in the Atlantic Ocean especially on the coast of Brazil

– The amount of red mud is less than blue mud.

c) Green Mud – When chemical weathering takes place in the ocean, the colors of the stones in it are converted into green.

– Formation occurs when chemical weathering occurs on the coast of the ocean

– Specially k (potassium) and s (silicate) can be seen in green mud.

– Some amount of iron is also found.

-It is seen more near Ireland area.

 -It is more common in coastal areas.

 – Its depth is 100-900 fathom.

Volcanic Deposits

There are TWO types

  1. On land
  2. On ocean

a) On land – Rock > weathering > erosion > transportation > deposition (in ocean area)

b) On ocean – direct eruption, he matches with blue mud. And these are of gray color.

Biotic Deposits

The deposits caused by organisms found in the internal part of the ocean are called biotic deposits.

  • It is called organic material because of the content of carbon in it.
  • Its source only ocean

There are TWO types of biotic deposits.

  1. Neretic Matter
  2. Pelagic Matter

a) Neretic matter– includes skeletons of organisms and plants.

b) Pelagic matter– Algae in this. Pelagic is known as ooze.

 There are TWO types of pelagic matter.

  1. Limestone
  2. Silica predominance

1. Lime Stone – Theropod ooze is from Mollusca organisms. It contains 80% carbonate. Its diameter is 1.5 inches. Globigerina ooze- its color is white. 65% is calcium carbonate. And depth 4000 fathom.

2. Silica predominance – Radiolarian ooze has a depth of 2000-5000f, and it lies between Indian Ocean and Atlantic Ocean. Depth of diatom ooze is 600-2000F. And Pacific Ocean has more and its color is light.

High Salinity

1. Red Sea -(37.41‰)

2.The Persian Gulf-(37.38‰)

Medium Salinity

1. Caribbean sea (35-36‰)

2.Bass Strait (33.5‰)

3. Gulf of California (35‰)

Low Salinity

– Polar area (20-35‰)

Atlantic Ocean (salinity)

  • Average salinity 35.6‰
  • 15-20 Here more salinity is found

Indian Ocean

  • Salinity is high at -0°-15°. (35‰)
  • The salinity increases to 30‰ as one approaches the Bay of Bengal area 36‰
  • In the Indian Ocean, higher salinity occurs in the western part of Australia/coastal area.
  • Vertical distribution – In the -30°-60° temperate region, the salinity increases as it goes 300-1000m deep and decreases beyond 1000m.
  • Salinity remains equal after 300-1000m depth at Equator
  • The line which is used as base for measuring salinity is called Halocline.

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