Sea-level changes:
Rising or lowering of sea level for a longer period[ not like tides] is called sea-level changes or Eustatic Changes.
There are two types of sea-level changes:
- Sea Level Rise
- Sea Level decrease
The following are the two major reasons for the sea level rise:
- Isostatic adjustment of land and ocean
- Global warming
Isostatic adjustment of land and ocean:
- Due to the overloading of glacial ice, large parts of the land sink into the ground, due to which the sea level rises.
- Sea level rises because of the huge sedimentary deposition from continents by rivers or winds.
Global Warming:
Global warming causes two major problems:
- The melting of glacial ice increases the amount of water in the ocean, due to which the sea surface rises.
- The increase in sea surface temperature leads to the thermal expansion of water leading to a rise in sea level.
Sea Level fall:
Sea level fall due to two major reasons:
- Global cooling
- Upliftment of landmass
Global cooling
- In the Global cooling period, there is a reduction of insolation due to various reasons such as large-scale volcanic eruptions, or spread of space dust, or the reduction of Green Houses Gases; which leads to the thermal contraction of ocean water and the formation of glacial ices at higher latitudes; which cause fall in sea level.
- Carboniferous and Pleistocene times was global cooling time.
Upliftment of landmass:
The melting of ice glaciers on landmass also causes the sea level to fall as it releases the loads from the land; that causes the rising of the landmass and an apparent fall in sea level.
The melting of ice glaciers on landmass also causes the sea level to fall as it releases the loads from the land; that causes the rising of the landmass and an apparent fall in sea level.
For example,
Hazards associated with rising sea-surface temperature:
- Scandinavia is still rising due to the release of glacial ice.
- The formation of lofty mountains leads to an apparent fall in sea level.
- A drop of 1 degree in global temperature results in a 2-meter drop in sea level.
- There is an increase in the land area in the coastal areas.
- Changes are seen in the erosion and deposition processes
At present, we are experiencing a global warming phenomenon, and the sea level rising.
Try to solve the following questions:
- Discuss the hazards associated with the rising sea-surface temperature. ( UPSC 2021 geography paper 1, 10 Marks, 150 words)
- Describe the causes and consequences of sea-level changes. (UPSC 2018, 150 words, 10 marks)
Answer:
Sea-surface temperature
- The sea-surface temperature of the ocean varies with latitude. In general, the warmest water is found near the equator and the coldest waters are found in higher latitudes near Arctic and Antarctic regions.
- Due to global warming, sea-surface temperatures have risen steadily in the last 5 decades.
The following are hazards associated with the rising sea-surface temperature:
- Atmospheric hazards:
- Cyclone
- Floods
- Droughts
- Climate change
- Changes in the Marine ecosystem:
- Coral Bleaching.
- Changes in global conveyor belts.
- Harmful bacterial growth and the contamination of seafood.
- Sea level rise:
- Thermal expansion of water.
- Melting of Glaciers.
- Coastal Modifications.
Atmospheric hazards:
As we know ocean water continuously interacts with the atmosphere through the convection and radiation process, and the exchange of heat happens between ocean water and the atmosphere. The rise in sea-surface temperature creates the following atmospheric hazards:
Risk of heavy rains and drought in some areas:
- The rise in sea temperature leads to an increase of water vapor in the atmosphere which causes changes in weather phenomena. Some regions may get increased rain and other regions may be affected by drought.
Increase in tropical cyclones:
- The rise of sea temperature increases the frequency of tropical cyclones. We have noticed that year by year number of tropical cyclones is increasing in the Bay of Bengal as well as the Indian Ocean. India is facing major hazards from tropical cyclones.
- As per the IPCC( Intergovernmental Panel on Climate Change) 2021 report, there will be a rise of 7 % in intensified extreme weather such as cyclones, an increase in the heatwave, shorter cold season due to a 1-degree centigrade rise in sea temperature.
Changes in the Marine ecosystem:
- Rising sea surface temperatures can affect the plant, coral, fish, and bacterial species present in marine ecosystems.
- Corals are very sensitive to temperature, a rise in sea level will increase coral bleaching which will lead to a decline in fish production.
- The rise in ocean temperature increases the number of certain bacteria as well as the number of new viruses, which increases the risk of contamination of seafood and will lead to an increase in food-borne diseases.
Sea level rise:
- An increase in sea-surface temperature leads to thermal expansion of water and it melts glaciers leading to rising sea levels. As per the various reports, most sea islands are at risk of submergence due to the rise of sea level.
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