OCEAN: TEMPERATURE DISTRIBUTION, SALINITY DISTRIBUTION, DENSITY AND TIDE

OCEAN: TEMPERATURE DISTRIBUTION, SALINITY DISTRIBUTION, DENSITY AND TIDE

OCEAN TEMPERATURE

The study of temperatures of oceans is the subject matter of massive meteorology, which deals with that portion of the atmosphere that overspreads the great water masses.

The temperature of the sea and its accurate measurements are an important task, as it helps in the determination of the movements of large masses of ocean water.

The ocean water is heated by three processes:

1. Absorption: Of sun’s radiation.
2. The conventional currents: Since the temperature of the earth increases with increasing depth, the ocean water at great depths is heated faster than the upper water layers. So, convectional oceanic circulations develop causing the circulation of heat in water.
3. Friction: Heat is produced due to friction caused by the surface wind and the tidal currents, which increase stress on the water body.

Factors Affecting Distribution of Ocean Water Temperature

• Latitude: The surface temperature of the oceans declines from the equator towards the poles as the Sun’s rays are vertical on the equator and become slanting as one moves towards the poles.
• Change of season: The effect of season is far more pronounced in air than in water. Ocean water records a seasonal range of only 1.2° Celsius between 20° and 30° latitudes. The range is still 1.2° Celsius beyond 50° latitudes.
• Enclosed Seas: The enclosed seas (Marginal Seas—Gulf, Bay, etc.) in the low latitudes record relatively higher temperatures than the open seas, whereas the enclosed seas in the high latitudes have lower temperatures than the open seas.
• Ocean Currents: Warm ocean currents raise the temperature in cold areas, while cold currents decrease the temperature in warm ocean areas.
  • For Example: Gulf Stream does not allow the Norway coast to freeze even in winter.
• Prevailing Winds: The direction of the prevailing winds, such as the Trade Winds, Westerlies, etc., determines the surface temperature of ocean waters at a point.
  • For Example: Eastern edges of the ocean along the trade wind belt have cooler waters due to the pushing of the warm waters by the trade winds away from the coast, causing the upwelling of bottom waters.
• Unequal distribution of Land and Water: The Northern Hemisphere has more land area than the Southern Hemisphere. Consequently, the oceans of the Northern Hemisphere are warmer than those of the Southern Oceans.
• Shape of the ocean: The latitudinally extensive seas in low latitude regions have warmer surface water than longitudinally extensive seas.
  • For Example: The Mediterranean Sea records higher temperatures than the longitudinally extensive Gulf of California.

• The density of water: The density of ocean water is mostly a function of its temperature and salinity. The density of waters also varies from latitude to latitude. In the areas of high salinity, the ocean waters are of a relatively higher temperature and vice versa.
• Iceberg: Icebergs found near polar areas can be seen floating up to 50° latitude. It lowers the temperature of water at great depth.
• Effect of land mass: Small cities are affected by adjacent land masses. The temperature rises in summer and falls in winter because of the influence of land masses.
• Insolation: The average daily duration of insolation and its intensity.
• Heat loss: The loss of energy by reflection, scattering, evaporation, and radiation.
• Albedo: The albedo of the sea (depending on the angle of sun rays).
• Local Factors: Submarine ridges, local weather conditions like storms, cyclones, winds, fogs, cloudiness, the rate of evaporation, lapse rate, condensation, and precipitation also affect the distribution of temperature of the oceans.

Horizontal ocean temperature distribution

• Isothermal lines: The horizontal temperature distribution is shown by isothermal lines, i.e., lines joining places of equal temperature. Isotherms are closely spaced when the temperature difference is high and vice versa.

Observations:

• Average surface temperature: The average temperature of surface water in the oceans is 26.7°C, and the temperature gradually decreases from the equator towards the poles.
• Rate of change with respect to latitude: The rate of decrease in temperature with increasing latitudes is generally 0.5°C per latitude.
• Variation with latitude: The average temperatures become 22°C at 20° N and S latitudes, 14°C at 40° N and S latitudes, and 0°C near the poles.
• Ocean temperature: The average annual temperature of all the oceans is 17.2°C.

• North-South ocean variation: The average annual temperatures for the northern and southern hemispheres are 19.4°C and 16.1°C respectively.
  • Reason: The variation of temperatures in the northern and southern hemispheres is due to the unequal distribution of land and water. The Northern Hemisphere is made up of more land, while the Southern Hemisphere is made up of more oceans.
• Average annual range: The average annual range of temperature is about 12°C. The highest annual range of temperature is recorded in the North Atlantic Ocean. Moreover, the annual range of temperature is higher for the inland seas compared to open oceans.

Vertical ocean temperature distribution

• Conduction: The maximum temperature of the oceans is always on the surface because it directly receives insolation. The heat is transmitted to the lower sections of the oceans through the mechanism of conduction.
• Percolation of light energy: Only about 45% of light energy striking the ocean surface reaches a depth of about one meter, and only 16% reaches a depth of 10 meters. Based on the temperature, the ocean depths can be divided into the following three zones:
  • Photic Zone or Euphotic Zone: This is the upper layer of the ocean. The temperature is relatively constant and is 100 meters deep.
  • Thermocline: It lies between 100-1000 meters. There is a steep fall in the temperature. The following graph shows the thermocline.
  • Deep Zone: Below 1000 meters is the deep zone. Here, the temperature is near zero °C. Please note that near the bottom, the temperature of the water never goes to 0°C. It is always 2-3°C.

Observations:

• Rate of change not uniform with depth: Sea temperature decreases with increasing depth, but the rate of decrease of temperature is not uniform.
• Rate of change negligible after thermocline: The change in sea temperature below the depth of 1000 meters is negligible. The maximum change in temperature occurs between 100-1000 meters, which is called the Thermocline or Pycnocline.

• Diurnal and annual ranges: Diurnal and annual ranges of temperature cease after a depth of 30 feet and 600 feet respectively.
• At pole and equator: The rate of decrease in temperature with increasing depth from equator towards the poles is not uniform. Though the surface temperature of the oceans decreases from the equator to the poles, the temperature at the ocean bottom is uniform at all latitudes.
• Exception: However, some studies have shown that the coldest bottom temperatures, just below -0.25°C, occur at 60-70°S, near the Antarctic continent.

SALINITY

The weight of the dissolved materials divided by the weight of the sample seawater is known as salinity. Generally, salinity is defined as the total amount of solid material (present in the dissolved form) in grams contained in one kilogram of seawater and is expressed as part per thousand.

Sources of salinity:

• Continental landmass: The salts dissolved in ocean waters have their origin in the continental landmasses. They can be carried into the oceans by rain, rivers, groundwater table, sea waves, winds, and glaciers.
• Ocean bottom: Some of the dissolved salts have their origin from the ocean bottom. The layers of the earth beneath the crust contain minerals in a molten state, which can reach the crust either due to volcanic activity or due to their outgassing (continuous emission in the form of gases) from fissures present at the bottom of the ocean.
• Decompose of organic matter: The dead and decomposing organic matter also adds to the salinity of the oceans.

Variation in Composition: There is a lot of variation in the composition of Riverine salt and Sea salt. Riverine salt contains more CaSO₄ (60%) and sea salt contains more NaCl (77.8%). With further studies, geographers found that the following reasons are responsible for the difference in composition:

• Major portion of the calcium carried by the river is consumed by river organisms.
• The salt carried by the river is modified in the ocean.

Factors Controlling the salinity:

• Evaporation: Higher the rate of evaporation, higher is the salinity. The highest evaporation has been recorded along the Tropic of Cancer, and that is one of the reasons that the region of the Red Sea and Persian Gulf has one of the highest salinity levels.
• Temperature: Higher temperatures are associated with high salinity. This is because high temperatures cause a high rate of evaporation of freshwater. As freshwater evaporates, the concentration of salt increases, which will give rise to more saline water in that region.
  • For Example: The Red Sea is one of the most saline bodies.
• Precipitation: Precipitation is inversely related to salinity. Higher precipitation results in lower salinity.
  • For Example: The equatorial region records the highest rainfall, which is why it has lower salinity compared to those which are nearer to the tropics.

• Influx of Freshwater: Seas and oceans with large river inflow have a low level of salinity. Rivers bring continuous freshwater to the seas, which plays a major role in reducing the salt levels in the water.
  • For Example: The Bay of Bengal is less saline in comparison to the Arabian Sea due to the drainage of large rivers such as the Ganges, Brahmaputra, Irrawaddy, etc., into it.
• Enclosure of land: Seas with land surrounding them are found to be more saline compared to open seas. This is because land prevents the free mixing of new water and plays an important role in dispensing heat into the water body, increasing evaporation levels.
  • For Example: The Persian Gulf is highly saline due to the surrounding land.
• Atmospheric Pressure: Anticyclonic conditions with stable air and high temperature increase the salinity of surface waters of the oceans.
  • For Example: High salinity conditions can be found in subtropical high-pressure belts.
• Ocean Currents: Ocean currents continuously engage in bringing new water and taking away old water, creating a form of water circulation. Ocean currents that bring fresh water reduce salinity in a given region. Similarly, warm currents are more saline in nature.
  • For Example: The Labrador current reduces salinity.

Horizontal Distribution of Salinity:

• Salinity decrease near tropics: As a general rule, the surface salinity of oceans decreases on either side of the tropics. For instance, the surface salinity along the Tropic of Cancer is around 36 parts per thousand (ppt), while at the equator it’s around 35 ppt.
• Highest salinity: The highest salinity of seawater has been recorded between 20°N to 40°N.
• North-South variation: The average salinity of the Northern Hemisphere and Southern Hemisphere is 3.5‰ and 3.4‰ respectively, mainly because the Northern Hemisphere is land-dominated.

On the basis of salinity levels, seas across the world can be categorized as follows:

• Seas with low salinity levels: They have low salinity due to the influx of freshwater. These include the Arctic Ocean, Southern Ocean, Bering Sea, Sea of Japan, Baltic Sea, etc. Their surface salinity can be as low as 21 ppt.
• Seas with normal salinity levels: They have a salinity in the range of 35 to 36 ppt. These include the Caribbean Sea, Gulf of Mexico, Gulf of California, Yellow Sea, etc.
• Seas with high salinity levels: They have higher levels of salinity due to their location in regions with higher temperatures, leading to greater evaporation. These include the Red Sea (39-41 ppt), Persian Gulf (38 ppt), Mediterranean Sea (37-39 ppt), etc.

Vertical Distribution of Salinity:

• No definite trend: There is no definite trend in the variation of salinity with depth. Instances of both increase and decrease in salinity levels have been found with increasing depth.
  • Higher latitude: Salinity of the ocean increases with increasing depth in the higher latitudes and polar areas.
  • Middle latitude: In the middle latitudes, the same trend is seen, but only up to a depth of 370 meters. After that, it decreases with increasing depth.

SALT BUDGET

Meaning: It is also known as the salt cycle. It involves all the processes through which salt moves from the ocean into the lithosphere, to a certain extent into the atmosphere, and back into the oceans.

Process:

• Surface erosion makes salt reach the ocean: Moving water, including groundwater, leaches minerals from rocks through the process of surface erosion. The mineral-laced water joins rivers and streams, which finally reach the oceans. These minerals add to the salinity levels of ocean waters.
• Accumulation of salt at ocean bottom: Some of the salts in ocean waters accumulate at the ocean bottom through the process of sedimentation, turning into mineralized rocks.
• Ocean bottom also contributes to salt: Over millions of years, some of these rocks get raised above the ocean surface due to plate tectonics or volcanic activity. This brings the salt back to the lithosphere in the form of minerals (rocks).
• Salt moves to the atmosphere: Salt from the oceans also gets sprayed into the atmosphere due to wind action. This salt returns to the lithosphere mixed with precipitation. However, this constitutes a tiny fraction of salt moving from land to sea and vice versa.

The salt cycle operates over a very long period of time. Every year, around 3 billion tons of salt gets added to the oceans from the land. A tiny fraction of this salt is extracted by humans for daily consumption.

DENSITY OF OCEAN WATER

The density of ocean water is determined mainly by temperature, salinity, and pressure. However, regional factors also determine water density. These further govern the vertical movement of ocean water, resulting in its stratification according to density.

• Temperature: Depends upon the heat exchange between the sea surface and atmosphere. At higher temperatures, water expands, reducing its density, while lower temperatures increase the density of water. Thus, water at the poles is denser than in the tropics.
• Salinity: High salinity seawater is denser and sinks below lower salinity water, leading to stratification.
• Pressure: Increasing density values demonstrate the compressibility of seawater under the tremendous pressures present in the deep ocean.

• Influx of water: Rainwater, surface run-off brought by rivers flowing into oceans, and meltwater from ice and snow are minor factors that lower down density.
• Change of matter: Evaporation, cooling of surface water, and the process of ice formation tend to increase the density of ocean water.
  • For Example: In the tropics, they have higher evaporation resulting in higher density, while near the poles they have lesser evaporation, resulting in comparatively low density.

Distribution of Density of Sea Water

1. Latitudinal Variation:
   • Middle latitude: Between 20° and 30° N and S, water has high salinity due to a high rate of evaporation, leading to higher density.
   • Higher latitude: Temperature of surface ocean water decreases between 45° N-S and the poles. Lower surface temperature corresponds to higher water density.
   • Equator: Salinity is lower than the average 35% in equatorial waters due to high daily rainfall and high relative humidity.
2. Vertical Distribution:
   • The vertical distribution of density reveals that generally, surface water of low density is found, which increases in density towards the bottom. It is because any amount of water that finds itself among less dense water will sink automatically below the surface up to the depth where water of similar density is found.
   • Hence, at places of convergence, dense water mass sinks below the lighter one and forms bottom water.

TIDES

The periodic short-term rise and fall in sea level are known as tides. It is produced due to the gravitational interaction of the Earth, Sun, and Moon. Since the Moon is closer to the Earth, it has a pronounced influence on the tides. The rotation of Earth also aids in forming tides.

There are three major forces causing the occurrence of tides. They are:

• Moon’s gravitational pull
• Sun’s gravitational pull
• Centrifugal force, which acts opposite to the gravitational pull of the Earth.

Generation of Tide:

• Imbalance in forces: When the two forces are not in balance, it gives rise to the tide-generating force. The side of the Earth that is closest to the Moon has the strongest gravitational attraction towards the Moon, while water on the opposite side of the Earth experiences a weaker gravitational force.
• Moon has a greater effect: The Moon’s gravitational force has a greater effect than the Sun’s gravitational force due to the relative distance of the Moon and Sun. The tide-generating force is proportional to the product of the masses of the two bodies but also inversely proportional to the square of the distance between them.

Types of Tides

1. Based on Position of Moon and Earth:
   • Spring Tide: It occurs during the full moon and new moon days when the sun, the moon, and the earth are in the same line twice each lunar month all year long, without regard to the season.
   • Neap Tide: It occurs when the moon is in its first and last quarter, causing ocean waters to be drawn in diagonally opposite directions by the gravitational pull of the sun and earth, resulting in low tides.
2. Types Based on Frequency:
   • Semi-diurnal Tide: This is the most common tidal pattern, featuring two high tides and two low tides each day.
   • Diurnal Tides: Only one high tide and one low tide each day. The successive high and low tides are approximately of the same height.
   • Mixed Tide: Tides that have variations in heights are known as mixed tides. They generally occur along the west coast of North America and in the Pacific Ocean.
3. Types Based on Magnitude:
   • Perigee: When the moon’s orbit is closest to the earth, it is called perigee. During this period, unusual heights of high and low tides occur.
   • Apogee: When the moon’s orbit is farthest from the earth, it is called apogee. Tidal ranges will be much less than average height during this period.
   • Perihelion: It is the position where the earth is closest to the sun (around January 3rd). Unusually high and low tides occur at this time.
   • Aphelion: It is the position where the earth is farthest from the sun (around July 4th). Tidal ranges will be much less than the average height during this period.

Stages of Tidal Changes:

• High tide: The stage when the tidal crest arrives at a particular location on shore, raising the local sea level.
• Low tide: The stage when the trough arrives, lowering the local sea level.
• Flood tide: A rising or incoming tide between low tide and high tide.
• Ebb tide: A falling or outgoing tide between high tide and low tide.

Factors Controlling the Nature and Magnitude of Tides:

• The movement of the moon in relation to the earth.
• Changes in the position of the sun and moon in relation to the earth.
• Uneven distribution of water over the globe.

• Irregularities in the configuration of the oceans:
  • For Example: Funnel-shaped bays greatly change tidal magnitudes. When the tide is channeled into bays and estuaries, they are called tidal currents.

Characteristics of Tides:

• The tidal bulges on wide continental shelves have greater height.
• In the open ocean, tidal currents are relatively weak.
• When tidal bulges hit the mid-oceanic islands, they become low.
• The shape of bays and estuaries along a coastline can also magnify the intensity of tides.
• Funnel-shaped bays greatly change tidal magnitudes. Example: Bay of Fundy — Highest tidal range.
• The large continents on the planet block the westward passage of tidal bulges as the Earth rotates.
• Tidal patterns differ greatly from ocean to ocean and from location to location.

Importance of Tides:

• Navigation: High tides are helpful for tidal ports that have shallow water, which is a constraint for big ships to enter.
  • For Example: Diamond Harbour in West Bengal and Kandla in Gujarat are examples of such ports.
• Fishing: High tides also help in fishing. Many more fish come closer to the shore during high tide, which helps fishermen get a plentiful catch.
• Desilting: Tides help in desilting sediments and in removing polluted water from river estuaries.
• Tidal energy: Tidal currents are a very potential source of tidal energy, which is harnessed by many developed countries on a large scale and to some extent in India as well.
  • For Example: A 3 MW tidal power project was constructed at Durgaduani in Sundarbans of West Bengal.
• Keep harbor unfrozen: Saltwater freezes at a lower temperature than freshwater. In cold regions where rivers are frozen in winter, the warmer seawater rushes into the harbors to keep them from freezing.
• Calm climatic conditions: Tides stir ocean water, creating habitable climatic conditions and balancing temperatures on the planet.

MOON ‘WOBBLE’ AFFECTING RISING TIDES

When the Moon makes its elliptical orbit, its velocity varies, causing our perspective of the “light side” to appear at slightly different angles. This phenomenon is called the Moon’s wobble or oscillation, which is a cyclical shift in the Moon’s orbit.

Occurrence of Wobble:

• Two tides: High tides on Earth are caused mostly by the pull of the Moon’s gravity on the spinning Earth. On most beaches, you will see two high tides every 24 hours.

• Moon’s revolution: The moon also revolves around the Earth about once a month, and that orbit is slightly tilted.
• Inclination of Moon’s orbit: The moon’s orbital plane around the Earth is inclined approximately 5 degrees to the Earth’s orbital plane around the sun.
• Nodal Cycle: Because of this, the path of the moon’s orbit seems to fluctuate over time, completing a full cycle—sometimes referred to as a nodal cycle—every 18.6 years.
• Rise in tide: At certain points along the cycle, the moon’s gravitational pull comes from such an angle that it pulls one of the day’s two high tides a little higher, at the expense of the other.
• Pulling of ocean: This does not mean that the moon itself is wobbling, nor that its gravity is necessarily pulling at our oceans any more or less than usual.

Impact of Wobble:

• Influences the ebb and flow of tides: The moon’s wobble impacts its gravitational pull, indirectly influencing the ebb and flow of tides here on Earth.
• Reverse the trend: One half of the 18.6-year cycle suppresses the tides, meaning the high tides get lower while the low tides get higher than usual.
• Intensification of tides: Once this cycle completes, the situation flips—in the subsequent cycle, tides are amplified, with high tides getting higher and low tides lower.

TIDAL BORE

• A tidal bore is a large wave or bore caused by the constriction of the spring tide as it enters a long, narrow, shallow inlet. These waves are resultant of the forces and turbulence that create a rumbling roar.
• Tides also occur in gulfs. Gulfs with wide fronts and narrow rears experience higher tides.
• The in-and-out movement of water into a gulf happens through channels called tidal currents.
• When a tide enters the narrow and shallow estuary of a river, the front of the tidal wave appears vertical due to the piling up of river water against the tidal wave and the friction of the river bed.
• The steep-nosed tide crest looks like a vertical wall of water rushing upstream and is known as a tidal bore.
• Tidal bores occur in relatively few locations worldwide, usually in areas with a large tidal range, typically more than 6 meters (20 ft) between high and low water.
• A tidal bore takes place during the flood tide and never during the ebb tide. Tidal bores almost never occur during neap tides. Neap tides happen during quarter moons when tides are weakest.
  • For Example: In India, tidal bores are common in the Hooghly River. The most powerful tidal bores occur in the Qiantang River in China.

Favourable Conditions:

The favorable conditions for a tidal bore include the strength of the incoming tidal wave, the slim and depth of the channel, and the river flow.

• Exceptions: The Amazon River is the largest river in the world. It empties into the Atlantic Ocean. The mouth of the Amazon is not narrow, but the river still has a strong tidal bore. A tidal bore develops here because the mouth of the river is shallow and dotted by many low-lying islands and sand bars.

Impact of Tidal Bore:

• Less predictable: Tides are stable and can be predicted. Tidal bores are less predictable and hence can be dangerous.
• Impact shipping: Tidal bores adversely affect shipping and navigation in estuarine zones.
• Capsize boats and ships: Tidal bores of considerable magnitude can capsize boats and ships of considerable size.
• Impact fishing: Strong tidal bores disrupt fishing zones in estuaries and gulfs.
• Affect ecology: Tidal bores have an adverse impact on the ecology of river mouths. The tidal bore-affected estuaries are rich feeding zones and breeding grounds for several forms of wildlife.
• Affect animals: Animals slammed by the leading edge of a tidal wave can be buried in silty water. For this reason, carnivores and scavengers are commonly seen behind tidal bores.

OCEAN AND ITS RESOURCES

Types:

• Food Resources: The ocean is the reservoir of all organisms required for human consumption, like fish, shrimp, and crabs.
• Plant Resources: Various varieties of commercial species like kelp, seagrass, and seaweed are obtained and farmed from the oceans.
• Industrial Resources: The oceans are also sources of various industrial resources like gypsum, limestone, and sand, which are abundantly used in the construction industry.
• Pharmaceutical Resources: Many medicines and cosmetics are sourced from biotic and abiotic ocean resources, including 5,300 different natural products and new compounds isolated from marine sponges.
• Salt: It is one of the most abundant minerals found in ocean water. Salt can either be directly extracted or mined, depending on the region.
• Water: In countries like Israel and Kuwait, ocean water is utilized for drinking and industrial purposes after proper filtration and desalination.
• Energy: The ocean is the source of many energy resources like crude, coalbed methane, and natural gas. Coal reserves are also six times greater than petroleum and oil reserves beneath the sea.
• Minerals: Polymetallic nodules of rare earth minerals and other minerals are also abundantly found on the ocean floor and continental shelves.

Importance/Relevance of Ocean Resources

1. Social:
   • Food Security: Many communities rely on seafood and oceanic plant species for daily dietary nutrition and existence.
     • Example: Coastal communities are also large consumers of fish and marine-based animals.
   • Livelihood: The ocean is also a provider of employment to millions of fishermen and those associated with the fishing industry.
     • Example: Fishing in India is a major industry employing 14.5 million people. India ranks second in aquaculture and third in fisheries production.
2. Economic:
   • Share in GDP: The marine-based economy contributes to a significant share in national exports and revenue.
     • Example: Fisheries contribute 1.07% of the total GDP of India.
   • Trade and Logistics: The 8000 km coastline also ensures ample opportunities for port-led logistics and global trade as well as regional development.
   • Tourism: Ocean resources in terms of aesthetic value like beaches, reefs, and islands also provide huge revenue from tourism.
   • Precious Metals and Gems: Ocean is a key contributor towards the mining of gold and silver; also, precious gems like diamonds and pearls are derived from offshore sites.
3. Energy:
   • Energy Security: The world’s oceans are also sources of petroleum crude and natural gas, the most common sources of fuel and energy.
     • Data: In 2025, it is forecasted that 28% of the crude oil produced globally will be produced offshore.
   • Mineral Security: Many useful minerals, both industrial and non-industrial, are sourced from oceans and seas.
     • Example: Polymetallic Nodules found on the ocean floor.
   • Renewable Energy: Oceans also aid in generating renewable energy like hydropower, tidal power, and power generated from wave action.
4. Others:
   • Scientific Research: Oceans are key to understanding the impact of global warming on Earth, species migration, extinctions, and other geological processes.

Threats to the Ocean and its Resources

1. Global Warming:

• Surface Temperature Rise: Global temperature rise also impacts sea surfaces and makes the ecosystem less hospitable for a wide variety of organisms.
  • Example: A spike of 1-2°C in ocean temperatures sustained over several weeks can lead to coral bleaching, turning corals white. If corals are bleached for prolonged periods, they eventually die.
• Melting of Ice Caps: Melting ice caps lower the temperature of the seas. Harmful algal blooms are expected to increase as oceans warm. This disperses floating phytoplankton deeper into the water column, limiting their access to sunlight.

1. Anthropological:

• Deoxygenation: Climate change is making oceans hotter, promoting acidification, and making it harder to breathe for marine life by reducing dissolved oxygen levels.
• Ocean Acidification: Ocean acidification is a growing threat to marine life and humans. It results from the decreasing seawater pH due to the absorption of carbon dioxide (CO₂) from the atmosphere.
• Deep-Sea Mining Activities: The scraping of the ocean floor by machines alters or destroys deep-sea habitats, causing the loss of species and fragmentation of ecosystem structure and function.
• Wastewater: Untreated sewage flows into coastal waters, bringing organic waste and nutrients that deplete oxygen and cause disease.
• Plastic Pollution: Over five trillion pieces of plastic pollution are afloat in the oceans, and the Great Pacific Garbage Patch continues to grow.
  • Data: For every pound of tuna taken from the ocean, two pounds of plastic are put back.
• Dumping: Waste materials from industries, ships, and sewage plants pollute marine ecosystems significantly.
• Unsustainable Fishing: Nearly a third of global fish stocks are overfished. Once-abundant fish species, such as bluefin tuna, are now endangered. Illegal and unregulated fishing costs the global economy up to $23 billion annually.
• Dredging: Dredging disturbs the marine ecosystem by altering soil composition, destroying habitats of creatures and organisms.
• Subsidies: Governments spend $35 billion annually on fisheries subsidies, accelerating harmful overfishing by enabling overcapacity in fishing fleets.
• Oil Spills: Oil spills have polluted the marine ecosystem, killing marine species and impairing the water repellency of birds’ feathers, putting them at risk.

1. Others:

• Poor Protection: Marine protected areas are insufficient to reduce human activities’ impact on oceans.
  • Example: Only 2% of global oceans are strongly protected. Scientists suggest 30% protection is needed for future ocean health.
• Invasive Species: New animals settling in these areas compete with native species for space, shelter, or food and can cause physical damage.

Initiatives

India:

1. Ocean Services, Modeling, Application, Resources, and Technology (O-SMART): This initiative handles ocean development activities, such as technology, resources, services, science, and observation, and provides technological help for implementing the Blue Economy.

• Objectives

• Exploitation of resources: To develop technologies that will allow for the exploitation of marine bioresources, the generation of freshwater and ocean energy, and the development of undersea vehicles and technologies.
• Polymetallic Nodules: To conduct exploration of polymetallic nodules from a sea depth of 5500 meters in a 75,000-square-kilometer area granted to India by the United Nations in the Central Indian Ocean Basin, as well as to conduct gas hydrate investigations.

2. Deep Ocean Mission: One of the major objectives of this project is to mine and extract polymetallic nodules (PMN). The UN International SeaBed Authority has allotted India 75,000 sq. kilometers in CIOB for the exploration of these polymetallic nodules.
3. National Fisheries Policy: India has a National Fisheries policy for promoting the “Blue Growth Initiative,” which focuses on sustainable utilization of fisheries wealth from marine and other aquatic resources.
4. Blue Revolution 2.0 / Neel Kranti Mission: The focus of the Blue Revolution 2.0 is on the development and management of fisheries. This covers inland fisheries, aquaculture, marine fisheries including deep-sea fishing, mariculture, and all activities undertaken by the National Fisheries Development Board.

• Objectives: Fully tapping the total fish potential of the country, both in the inland and marine sectors, and tripling production by 2020.

5. Integrated Coastal Zone Management: It focuses on the conservation of coastal and marine resources, and improving livelihood opportunities for coastal communities.

International Initiatives

1. Sustainable Ocean Initiative (SOI): SOI will provide a global platform to build partnerships and enhance capacity to achieve the Aichi Biodiversity Targets related to marine and coastal biodiversity in a holistic manner.
2. The Global Partnership on Marine Litter (GPML): The GPML is a multi-stakeholder partnership that brings together all actors working to prevent marine litter and plastic pollution. By providing a global platform to share knowledge and experience, partners are able to work together to create and advance solutions to this pressing global issue.
3. UN Environment Programme (UNEP): Particularly through its Regional Seas Programme, UNEP acts to protect oceans and seas and promote the sustainable use of marine resources. The Regional Seas Conventions and Action Plans are the world’s only legal framework for protecting oceans and seas at the regional level.
4. Global Sustainable Fishing Initiative: Agreed by 14 countries to end harmful subsidies that contribute to overfishing. This initiative aims to eliminate illegal fishing through better enforcement and management, minimize bycatch and discards, and implement national fisheries plans based on scientific advice.
5. OECD’s Sustainable Ocean for All Initiative: To support the transition to a truly sustainable global ocean economy, in a way that benefits the poorest and most vulnerable countries, including small island developing states.

• Aim: To help align public and private finance with the goal of a sustainable ocean economy, through adequate domestic policies and international coordination.

6. World Economic Forum and Marine Science Institute of University of California Partnership: To improve the health of the world’s oceans and maritime resources. The new partnership aims to protect the world’s $2.5-trillion ocean economy.

Way Forward:

• Comprehensive baseline studies: Needed to understand what species live in the deep sea, how they live, and how they could be affected by mining activities. More funds are needed for training and educational programs focused on improving our understanding of the deep sea.
• High-quality environmental assessments: Needed to assess the full range, extent, and duration of environmental damage from deep-sea mining operations.
• 3R strategy on sea: The repair, recycling, and reuse of products should be encouraged to help reduce the demand for raw materials from the deep sea.
• Major achievements of India: India’s recognition as Pioneer Investor with the International Seabed Authority (ISA) for conducting extensive research on deep-sea mining of Poly Metallic Nodules (PMN) and hydrothermal sulfides in the allotted area of the Indian Ocean.
  • Desalination: The technology development for desalination using low-temperature thermal desalination, including the installation of such a facility in the Lakshadweep Islands.
• SDG: It calls to conserve and sustainably use the oceans, seas, and marine resources for sustainable development. India should look to adopt the Gandhian approach of balancing economic benefits with sustainability for meeting the broader goals of growth, employment generation, equity, and protection of the environment.