VIDEO Ocean Salinity Explained

The oceans are salty primarily due to the presence of sodium chloride (NaCl), also known as table salt.
There are many types of salts, resulting from compounds held together by ionic bonds.

Majority Component: 90% of ocean salts is sodium chloride (NaCl).
Other Salts: The ocean also contains magnesium, calcium, potassium, and sulfate (SO₄²⁻).

Rock Contribution: Salts originate from the weathering of rocks on land due to rainwater.
- Rainwater contains dissolved CO₂, making it slightly acidic, which helps in eroding rocks.
Water's Chemical Properties: Water (H₂O) is a polar molecule, meaning it has a negative charge on the oxygen side and a positive charge on the hydrogen side, which aids in dissolving salts.
As water flows from rain into streams, rivers, and lakes, it carries dissolved minerals and ions to the ocean.

Volcanic Activity: Underwater volcanoes and hydrothermal vents contribute to ocean salinity by dissolving basalt rocks, adding more salt.

Accumulation vs. Loss: The ocean retains more salt than what is lost. Although some organisms and basalt remove salt, the rates are not balanced.
Evaporation Effect: When water evaporates, it leaves the salt behind because the salt crystals do not evaporate with the water vapor.
Freshwater Input: Freshwater from rain falls into the ocean, maintaining the salinity around 3.5%, while some local lakes may have much lower salinity (e.g., <0.05%).

Hypothesis of Subsurface Water: There is a theory proposing that additional water may exist in the transition zone between the upper and lower mantle of the Earth, which scientists have been studying for decades.

Understanding ocean salinity involves several processes including erosion, dissolution, and evaporation, with contributions from both terrestrial and marine sources.