Upwelling & Downwelling, Water Mass and UNCLOS

Upwelling & Downwelling, Thermohaline Circulations, Water Mass and UNCLOS

Upwelling - 

• The offshore winds push the surface water away and causes the cold water from the bottom to rise up to the surface. 
• This brings the deep nutrients rich cold waters to the surface which helps in the growth of fish in a large scale.

Downwelling -

• The onshore winds pile up the water near to the coast causing the gradual sinking of water due to increase in density.

Upwelling is more active in the regions of cold ocean currents whereas downwelling is more active in the regions where both warm and cold ocean current meets.

Upwelling - water from bottom rising upward due to offshore winds which pushes away surface water from the coast.

Downwelling - water sinking to the bottom due to onshore winds which pushes the water towards the coast piling the water at the coast.

Thermohaline Circulation - 

Thermo - means Temperature & haline - means Salinity 🠊 i.e., it is the circulation/movement of ocean water due to difference in temperature and salinity.

Equatorial region - Temperature ↑ & Salinity ↑

Polar region - Temperature ↓ & Salinity ↓

These difference drives the ocean water.

Thermohaline circulations -

• The deep ocean currents driven by the difference in water density which is controlled by temperature and salinity is called Thermohaline circulation.
• It begins near to the polar regions where ice forms leading to the water saltier and denser resulting in sinking. 
• The deep water upwells in the regions of cold ocean current upwelling.
• This underwater current moves in a single and continuous belt across different oceans.
• They are called as Great Ocean Conveyor belts.

Difference between Ocean currents and Thermohaline circulation 

• Ocean Currents - Surface water circulations driven by mainly by winds
• Thermohaline Circulations - Deep water circulations driven by difference in temperature and salinity

Water Mass -

• It is a large body of water with distinctive characteristics of temperature and salinity.
• They can occur near to the surface or at intermediate level or at deep level.
• Water Masses help in maintaining uniformity of temperature, salinity and oxygen level which is important from the context of thermohaline circulation, upwelling and downwelling.

UNCLOS -

• Full form of UNCLOS is United Nations Convention on the Law Of the Sea.
• It is an international agreement that established the legal framework for marine and maritime activities in oceans.
• It demarcated the Oceans into 6 different categories -

1. Base line - It is the low water line which includes all lagoons and backwater as part of the land.
2. Internal water - It is the land ward side of the baseline.
3. Territorial sea - It is upto 12 nautical miles from the base line. A country exercises sovereign jurisdiction on the ocean water, surface as well as the air space, however innocent passage is allowed with certain restrictions.
4. Contagious zone - It is upto 24 nautical miles from the base line. A country exercises sovereign jurisdiction on ocean bottom and surface but not in the air.
5. Exclusive Economic Zone (EEZ) - It is upto 200 nautical miles. A country can exploit the resources along the ocean floor. In the regions where the continental shelf exceeds EEZ, the resource exploitation is allowed till the edge of the continental shelf.
6. High Sea - It is the international waters which is considered as the common heritage of all mankind. It is beyond the national jurisdiction of any country.

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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own. 

Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍