Horizontal Distribution Of Salinity in The Ocean

Salinity defines the total content of dissolved salts in seawater. We calculate it by determining the amount of salt (in grams) dissolved in 1,000 grams (1 kilogram) of seawater. We usually express it as parts per thousand or ppt. Salinity of 24.7 (24.7 o/oo) has been considered as the upper limit to demarcate ‘brackish water’.

Latitudinal Distribution:

The basic principle of salinity distribution is that it decreases from the equator to the poles.
Though the highest salinity is never found on the equator due to high rainfall, it is found maximum in the tropical regions.
These regions have high temperatures and humidity and less precipitation as compared to the equator.
At the Equator, the salinity is 34‰, while we find the highest salinity between 20 degrees to 40 degrees north.
Salinity decreases towards polar zones due to the influx of melting ice water.
The latitudinal distribution divides salinity into four zones: equatorial zones have relatively low salinity, tropical zones have maximum salinity, temperate zones have low salinity, and sub-polar and polar zones have minimum salinity.

Regional Distribution of Salinity:

Oceans are divided into three categories on the basis of salinity variation. These are:

Seas having higher salinity: Theses are the Red Sea, Mediterranean sea, and other enclosed seas.
Seas having normal salinity: Theses are Caribbean sea, Gulf of California, Gulf of Mexico, etc.
Seas having below normal salinity: The Arctic Ocean, Antarctica ocean, Bering sea, Andaman sea, Baltic sea, etc.

FAQs related with Horizontal distribution of salinity in oceans and seas

Ques 1. What factors contribute to the horizontal distribution of salinity in oceans and seas?

Ans. The horizontal distribution of salinity in oceans and seas is influence by several factors. These include the proximity to major river mouths, where freshwater input can lower salinity levels, as well as evaporation rates, which can increase salinity. Ocean currents also play a role in distributing salinity horizontally, as they transport water masses with different salinity levels across different regions.

Ques 2. How does the horizontal distribution of salinity affect marine ecosystems?

Ans. The horizontal distribution of salinity has significant implications for marine ecosystems. Organisms in marine environments have varying tolerances to salinity levels, and the availability of specific salinity ranges can determine the presence and distribution of different species. Changes in salinity can affect the growth and survival of marine organisms, including phytoplankton, zooplankton, and larger marine animals, potentially disrupting food chains and altering biodiversity patterns.

Ques 3. What are the potential consequences of human activities on the horizontal distribution of salinity?

Ans. Human activities can impact the horizontal distribution of salinity in oceans and seas. For example, excessive freshwater withdrawals from rivers for agriculture, industry, or domestic use can decrease freshwater input into coastal areas, leading to higher salinity levels. Additionally, the discharge of pollutants or industrial waste into water bodies can alter salinity levels and harm marine life. Climate change-induced sea-level rise and altered precipitation patterns can also influence salinity distribution, particularly in coastal regions, with potential consequences for coastal ecosystems and freshwater availability.