This question must have risen in everyone’s mind during childhood after accidentally gulping a mouthful of ocean water. It’s not recommended for anyone to directly taste ocean water, but you can try it right now by mixing a tablespoon of salt into one glass of water. Sounds ugh, right?

Evening view of the ocean
Evening view of the ocean

Over 70 percent of the earth’s surface is covered with ocean, 97 percent of which is found saline in nature. It is very thought-provoking that water found in the lakes and rivers is considered to be freshwater but when they channelize into oceans, the salinity increases on a major scale.

Scientists have developed different tools and equipment to measure a very small amount of things. There was an amazing discovery that water found in lakes, rivers, or ponds had a very tiny amount of salt dissolved in it. Let it be the water of any tiny puddle or stream, it was found to have a very petite amount of salt. There’s only one exception to it and that is rainwater. The water falling from the sky has no salt in it at all and is considered to be 100 percent completely freshwater.

It was found that when raindrops fall into the ground or trickles down into rivers and streams, that’s when it starts to become a little bit salty. Geologists (who study rocks and soil) figured out that most of the rocks and soil contain tiny amounts of salt and when the rainwater touches the ground, it absorbs some of that salt. When these lakes and rivers pour their water into the ocean, they carry their salt with them. With time, the salt gets accumulated into the ocean from which it never leaves.



The Saltiest Water Bodies On Earth

Don Juan Pond

It is situated in Antarctica. Saltiest water body among all of the world’s lakes, containing more than 40 percent of salt content, water never freezes even at the lowest temperature (-22 degrees Fahrenheit).

Don Juan Pond (Antarctica)
Don Juan Pond (Antarctica)

Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio, http://rapidfire.sci.gsfc.nasa.gov


Dead Sea

Most famous saline body in the world, also known as the “Salt Sea”. It is situated between Jordan and Israel. It is named the dead sea because no life can survive here due to the high salinity rate. 

The Dead Sea
The Dead Sea


Great Salt Lake

The largest Salt Lake in northern Utah. It is a great site for hiking and biking with marvelous views of the lake. 

The Great Salt Lake (Utah)
The Great Salt Lake (Utah)


Caspian and Aral Seas

It is situated in Central Asia. Both bodies have been a victim of environmental concerns in recent years like pollution and shrinkage of the water body. It has eventually led to the death of the fishes which once lazed in its waters. 

Caspian Sea
Caspian Sea


Mono Lake

It is situated in California, USA. It has great outdoors and is surrounded by many volcanoes and mountains, and has a rich birdlife.

The Mono Lake (California)
The Mono Lake (California)


High Ocean Salinity Level 

It is estimated that if the salt in the ocean could be extracted by any means and spread consistently over the Earth’s terrestrial surface, it would form a deposit of about 166 meters thick and 150 meters tall. From folk stories to mythology, every culture has its own story explaining how the oceans became salty. A cubic foot of seawater can yield as much as 2.2 lbs of salt after evaporation in comparison to 0.01lbs of salt in 1 cubic foot of freshwater harvested from a source like Lake Michigan.

The answer is really simple. Salt in the ocean comes from rocks and land.

Salinity due to weathering of rocks
Salinity due to weathering of rocks


How Rainfall is the Reason for Salinity

We all know that rainwater is 100 percent completely freshwater, then how is it the reason for salinity in the ocean? Raindrops while falling to the ground absorb carbon dioxide from the surrounding air. This causes the rainwater to be somewhat acidic due to the formation of carbonic acid. The acidic content in the rain gradually erodes the rock and takes away the minerals and salts in a dissolved state as ions after the chemical breakdown. Further, the rainwater pours into the rivers and lakes which eventually flows down to the oceans. Some of the dissolved ions are used up by the marine organisms and some remain for long periods which leads to an increase in their concentration over time. 

Rainwater - Source of freshwater
Rainwater – Source of freshwater

The two major ionic components of seawater are sodium and chloride making up 90 percent of all the dissolved ions in ocean water. The concentration of NaCl (salt) in seawater is around 28 grams per liter. In other words, every kilogram of seawater contains has 35 grams of dissolved salts (Seawater – Wikipedia, 2021). The most saline water body is the Red Sea, where evaporation rates are higher, has lower rainfall rates, and low river run-off due to confined circulation.

The surprising fact is that the isolated ocean bodies can be 10 times saltier than the salinity found in the case of the Dead Sea. The current standard for salinity is the “Reference Salinity” scale with the salinity expressed in units of “g/kg”.

Hydrothermal Vents: a possible source of salts

The freshly discovered hydrothermal vents are found to be the possible source of salinity in ocean water. It features on the peak of the oceanic ridge, where its minerals are possibly dissolved into the ocean. The seawater seeps into the rocks of the oceanic crust, becomes hot, and flows back into the ocean with mineral-rich water. It is also believed that the complete bulk of the oceans could trickle through the oceanic crust in around 10 million years. 

Hence, this is an essential process that leads to salinity in seawater. 

Hydrothermal vent
Hydrothermal vent


The Role of Submarine Volcanism

The eruption of volcanoes below the surface of the water is known as submarine volcanism. The process is quite similar to that of hydrothermal vents, reaction with magmatic material within the crust and dissolving most of its mineral components in the ocean basin.

Ocean Volcanism
Ocean Volcanism


Importance of Salinity in the Ocean

The density of ocean water is directly proportional to its salt content. Water consisting of high amounts of salt is relatively denser or heavier and bowls below less brackish warmer water. The vast amount of salinity can affect the crusade of ocean currents. The oceanic circulation of water regulates the world’s climate. It may also hamper the marine life, which may need to adjust its ingestion of brine. 

Diversity in the marine life
Diversity in the marine life

Seabirds drink saltwater, which is regulated through the salt glands present in their nasal cavities. However, whales can’t drink saltwater: their needs are met through feeding on whatever is stored in their prey. They have kidneys to process brackish water.

On the other hand, sea otters can drink brine because their kidneys are evolved enough to digest the salt. The water may be less saline in areas where there is melting of ice, flow from rivers and streams.

Nevertheless, deeper ocean water is more saline, as is seawater in areas with higher temperature, lower precipitation, and abundant evaporation. The ocean water salinity is closely linked to Earth’s water cycle, regulation of freshwater through evaporation and precipitation. Studies show that the level of ocean salinity increases with evaporation and the freezing of sea ice. Studies also show the chemical composition of the open seawater remains at a constant level. And this is primarily due to the stability in the principal elements that form the salt.

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