OUR OCEANS -हमारे महासागर

While there is only one global ocean, the vast body of water that covers 71 percent of the Earth is geographically divided into distinct named regions. 

The ocean contains….97% of Earth's water.

Less than 3% is freshwater; the rest is saltwater, almost all of which is in the ocean.

Freshwater on Earth-

 69% resides in glaciers, 30% underground, and less than 1% is located in lakes, rivers, and swamps. 

Salinity

A zone of rapid salinity increase with depth is called a halocline.

 Oceanic waters in polar regions have lower salinity content than oceanic waters in temperate and tropical regions.

The chlorinity-

Salinity can be calculated using the chlorinity, which is a measure of the total mass of halogen ions (includes fluorine, chlorine, bromine, and iodine) in seawater.

The average chlorinity is about 19.2‰, and, thus, the average salinity is around 34.7‰.

Hydrometers are used to measure the oceans salinity

Poles  enjoy less levels of salinity -

The polar areas experience very little evaporation and receive large amounts of fresh water from the melting of ice.

This leads to low levels of salinity, ranging between 20 and 32.

Salinity changes with depth, but the way it changes depends upon the location of the sea.

Salinity at the surface –

Salinity at the surface increases by the loss of water to ice or evaporation, or decreased by the input of fresh waters, such as from the rivers.

Salinity at depth–much fixed

Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’

There is a marked difference in the salinity between the surface zones and the deep zones of the oceans.

Salinity, generally, increases with depth and there is a distinct zone called the halocline (compare this with thermocline), where salinity increases sharply.

The salinity of the inland Seas and lakes is very high because of the regular supply of salt by ‘ the rivers falling into them.

Factors Affecting the Salinity of the Seawater-

There are many affecting factors such as the weather including evaporation, precipitation; rivers, winds, ocean currents, sea waves, and global warming.

1-Evaporation:

The rate of evaporation and salinity are positively related. It is observed that with higher the evaporation rate, the higher the salinity

2-Precipitation:

It is inversely proportional to salinity. Higher precipitation results in lower salinity and vice versa..

-The Influx of River Water:

Rivers reduce the salinity by diluting the salt concentration of the sea and ocean. If a number of rivers are flowing into a specific location of the ocean, then there is a high chance for low salinity.

3-Ocean Currents:

They affect the spatial distribution of ocean salinity. Oceanic currents affect the salinity by increasing and decreasing it. Oceanic currents have less impact on the enclosed sea’s salinity however the impact on the salinity of marginal seas with open sea ducts is significant.

4-Atmospheric Pressure and Wind Direction: 

Anticyclonic conditions generally raise the salinity of the oceanic surface water when it has stable air and a higher temperature.

At the high-pressure zone of subtropics, higher salinity can be observed. Winds and currents provide assistance in the redistribution of oceanic salinity.

5-Global Warming:

 Global warming threatens the overall stability of ecological balance, not only salinity.

 It affects many factors such as temperature, ice melting, and many more, which directly and indirectly impact the salinity of seawater.

Ocean acidification

 Ocean acidification is the  decrease in the pH value of the Earth's oceans, caused by the uptake of carbon dioxide (CO₂) from the atmosphere.

 Why Acidification?

The main cause of ocean acidification is the burning of fossil fuels.

Seawater is slightly basic (meaning pH > 7), and ocean acidification involves a shift towards pH-neutral conditions rather than a transition to acidic conditions (pH < 7).

Harmfull effects- 

The concern with ocean acidification is that it can lead to the decreased production of the shells of shellfish and other aquatic life with calcium carbonate shells, as well as some other physiological challenges for marine organisms.

Between 1751 and 1996, the pH value of the ocean surface is estimated to have decreased from approximately 8.25 to 8.14 

The  pH scale is logarithmic so a change of one in pH unit is equivalent to a tenfold change in H⁺ ion concentration).

 Mechanism to regulate Oceans-

1-United Nation's Sustainable Development Goal 14-SDG-14

To ensure that ocean acidification is minimized, the United Nation's Sustainable Development Goal 14 (Conserve and sustainably use the oceans, seas and marine resources."Life below Water") aims to ensure that oceans are conserved and sustainably used.

2-Indian Institute of Tropical Meteorology (IITM)-Pune

-Ocean Mean Temperature(OMT)

Ocean Mean Temperature(OMT) is measured up to a depth of 26 degrees isothermat depths varying from 50–100 metres.

It is measured with the help of satellites that orbit the earth.

In the Indian ocean, OMT is analysed by measuring the ocean thermal energy during the period from January to March.

Scientists from Pune’s Indian Institute of Tropical Meteorology (IITM) find that ocean mean temperature (OMT) has a better ability to predict Indian summer monsoon than the sea surface temperature(SST)

3-United Nations Law of the Sea Convention (UNCLOS)

UNCLOS is an international agreement that establishes a legal framework for all marine and maritime activities. It became effective in 1994.HQ-Montbay ,Jaimca

The convention has resolved several important issues related to ocean usage and sovereignty, such as:

• Established freedom-of-navigation rights
• Set territorial sea boundaries 12 miles offshore
• Set exclusive economic zones-EEZ up to 200 miles offshore
• Set rules for extending continental shelf rights up to 350 miles offshore
• Created the International Seabed Authority
• Created other conflict-resolution mechanisms (e.g., the UN Commission on the Limits of the Continental Shelf)

4-The United Nations Environment Programme (UNEP) –

The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system.

 It was establishedinStockhome 1972.

Objectives-

To provide leadership, deliver science and develop solutions on a wide range of issues, including

- Climate change,

-The management of marine and terrestrial ecosystems, and green economic development.

- As a member of the United Nations Development Group, UNEP aims to help the world meet the 17 Sustainable Development Goals.

5-The International Maritime Organization (IMO) is the key United Nations institution for the development of international maritime law. Its main task is to create a fair and effective, generally accepted and implemented legal framework for the shipping industry.

Marine shipping and pollution

To ensure that shipping is cleaner and greener, IMO has adopted regulations to address the emission of air pollutants from ships and has adopted binding energy-efficiency measures to reduce greenhouse gas emissions from international shipping.

These include the landmark International Convention for the Prevention of Pollution from Ships of 1973, as modified by a 1978 Protocol (MARPOL), and the 1954 International Convention for the Prevention of Pollution of the Sea by Oil.

7-The United Nations Office on Drugs and Crime (UNODC)-

The United Nations Office on Drugs and Crime (UNODC), through its Global Maritime Crime Programme (GMCP) combats transnational organized crime in Africa focusing on countering piracy of the Horn of Africa and Gulf of Guinea

8-The Global Ocean Commission-

The Global Ocean Commission was an international initiative between 2013 and 2016 to raise awareness, and promote action to address, the degradation of the ocean and help restore it to full health and productivity.

Functions-

 Its focus was on the high seas, the vast ocean areas that lie beyond the Exclusive Economic Zones of individual states.

-A Sustainable Development Goal for the Ocean^.

-No More Overfishing 

- Plastics - Keeping them out of the ocean

-Offshore Oil and Gas - Establishing binding safety standards and liability

 The Commission included senior political figures, business leaders and development specialists, and consulted and collaborated widely with a diverse group of constituencies, including ocean users, governments, scientists, economists, business leaders and trade unions.

9-The International Seabed Authority (ISA)

The ISA is to safeguard the international deep sea, the waters below 200 meters or 656 feet, where photosynthesis is hampered by inadequate light. 

The International Seabed Authority (ISA) is a Kingston, Jamaica-based intergovernmental body of 167 member states and the European Union established under the 1982 UN Convention on the Law of the Sea (UNCLOS) and its 1994 Agreement on Implementation.

Functions-

-To exercise oversight of activities that might threaten biological diversity and harm the marine environment. 

- To date, the Authority has not authorized any commercial mining contracts as it deliberates over regulations amid global calls for a moratorium on deep sea mining.

Scientists and environmentalists warn such mining could wreak havoc on the ocean as a carbon sink home to rare and diverse species.