Salinity in Ocean

Salinity in Ocean

The oceans are types of basins on the surface of the earth which containing saltwater. salinity is defined as the total amount of dissolved material in grams in one kilogram of seawater. The variability of dissolved salt is very small, and we must be very careful to define salinity in ways that are accurate and practical. salinity for most of the ocean’s water is varied from 34.60 to 34.80 parts per thousand (‰), which is 200 parts per million.

challenger mission (1884) described a total of 47 dissolved salt materials in the ocean. Most found salt materials are shown in the following chart-:

Salt matterTotal Quantity (In gram)(‰)
Sodium chloride27.2177.8
Magnesium chloride3.8010.9
Magnesium sulphate1.654.7
Calcium sulphate1.263.6
Potassium sulphate0.862.5
Calcium carbonate0.120.3
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salinity is directly proportional to the amount of chlorine in seawater, and because chlorine can be measured accurately by a simple chemical analysis, salinity S was redefined using chlorinity:

S = 0.03 + 1.805Cl

where chlorinity Cl is defined as “the mass of silver required to precipitate completely the halogens in 0.328 523 4 kg of the sea-water sample.

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Sources of Sea Saltness

Basically, there are major two sources of salt in ocean comes from runoff from the land and openings in the seafloor.

Different types of rocks present on the land are the major source of dissolved salt in seawater. Rainwater that falls on the land is slightly acidic, so it erodes rocks. This releases ions that are carried away to streams and rivers that eventually feed into the ocean.

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The second source of seawater salt is hydrothermal fluids, which come from vents in the seafloor.  Ocean water seeps into cracks in the seafloor and is heated by magma from the Earth’s core. The heat causes a series of chemical reactions. The water tends to lose oxygen, magnesium, and sulfates, and pick-up metals such as iron, zinc, and copper from surrounding rocks.

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Factors affecting seawater salt

There are several factors which directly or indirectly affects the presented salt level in sea water.

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1. Temperature:

the relationship between seawater salt and temperature is positive. In simple words, we may say that where the temperatures high, the process of evaporation is also very high which causes the presence of salt in seawater high. For example, due to the high temperature near the tropic of cancer and tropic of Capricorn the level of saltness is very high as compared to poles.

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2. Rainfall

Rainfall is another important factor that controls the amount of salt in seawater. For example, near the equatorial region, the rainfall is very high which reduces the amount of seawater on the surface of the ocean near the equator. There in the equator, the precipitation is high as compared to evaporation.

3. River water

At the Estuaries the amount of salt in seawater is less.

4. Air pressure and Wind

Winds are an important factor that affects the amount of seawater in the ocean. Winds move the seawater from one place to another one. The place where the water is moved has a low amount of sea salt and the place where the seawater is shifted has a high slat amount.

5. Ocean movement

Oceanic movements are also affecting the amount of seawater. Such as ocean currents, North Atlantic flow causes a high amount of sea salt in the North Sea.

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Figure 1. worldwide annual amount of seawater salt.

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