Rising sea levels and associated threat

What’s in today’s article?

• Why in news?
• Rise in Sea Level
• How much is the sea rising?
• What causes accelerated sea-level rise?
• What problems will sea-level rise cause?
• How will sea-level rise affect societies?

 

Why in news?

• The World Meteorological Organization (WMO) has found in a new report that the world’s sea level is rising at an unprecedented rate.
  • The report, entitled ‘State of the Global Climate 2022’, was published recently.
• Along with accelerating sea-level rise, the report focused on:
  • a consistent rise in global temperatures,
  • record-breaking increases in the concentration of greenhouse gases as well as glacier loss,
  • sustained drought-like conditions in East Africa, r
  • record rainfall in Pakistan, and unprecedented heatwaves that struck Europe and China in 2022.

 

Rise in Sea Level

How much is the sea rising?

• As per the report, released by the WMO, the rate of global mean sea-level [GSML] rise has doubled between the first decade of the satellite record and the last.
  • Since the 1990s, scientists have been measuring sea-level rise using satellite altimeters.
  • These instruments send radar pulses to the sea surface and measure the time they take to get back and the change in their intensity.
  • The higher the sea level, the faster and stronger the return signal.
• While the rate of sea-level rise was 2.27 mm/year in 1993-2002, it shot up to 4.62 mm/year in 2013-2022.

 

What causes accelerated sea-level rise?

• Primarily due to Global warming
  • Accelerated sea-level rise is primarily caused by global warming, which is driven by the increasing concentrations of greenhouse gases.
  • These gases trap heat from the sun and warm the Earth's surface.
  • This leads to a wide range of climate impacts, including:
    • melting glaciers and ice sheets,
    • thermal expansion of the ocean water, and
    • changes in ocean currents and circulation patterns.
  • According the report of WMO, Ocean warming – the phenomenon of rising mean ocean temperatures – contributed 55% in accelerated sea-level rise.
• Melting of land-based ice
  • Melting of land-based ice, particularly the Greenland and Antarctic ice sheets, is a significant contributor to sea-level rise.
    • The report also says that the earth’s ice cover, known as the cryosphere, has thinned.
    • The cryosphere includes:
      • the Arctic and Antarctic regions (called “sea ice”), glaciers,
      • the ice sheets of Greenland and Antarctica (area of ice on land covering more than 50,000 km2),
      • seasonal snow cover, and
      • permafrost (mass of land that remains below 0º C for at least two straight years).
  • As these ice sheets melt, they discharge vast amounts of water into the ocean, leading to a rise in sea level.
  • According to the report, in 2005-2019, loss of glaciers and ice sheets contributed 36% to the GSML rise.
• Ocean warming
  • As GHGs drive global warming, 90% of the extra heat is stored in the oceans.
  • This leads to ocean warming. And as the ocean heats up, it undergoes thermal expansion leading to a rise in the GSML.
• Earth's gravitational and rotational fields
  • Additionally, changes in the Earth's gravitational and rotational fields can also affect sea level regionally.
• Human activities
  • Human activities, such as burning fossil fuels and deforestation, are the primary drivers of global warming, and thus the main cause of accelerated sea-level rise.

 

What problems will sea-level rise cause?

• Pressure on land
  • As rising seas swallow more of the land cover, particularly in coastal areas, coastal communities will face an acute shortage of land for human use.
• Increased flooding and erosion
  • Low-lying coastal areas will become more vulnerable to flooding and erosion, leading to damage to buildings, infrastructure, and natural habitats.
• Saltwater intrusion
  • Rising sea levels can also cause saltwater to infiltrate into freshwater aquifers and ecosystems, leading to a decline in water quality.
  • It will affect the availability of water for agriculture, drinking, and industrial use.
• Increased frequency of cyclones
  • Weather formations like cyclones are known to typically originate in the open seas.
  • As the GSML continues to rise, along with a rise in ocean temperatures, the chances of cyclones could increase.
• Displacement of coastal communities
  • Sea-level rise may force millions of people living in low-lying coastal areas to relocate to safer areas.
• Loss of biodiversity and ecosystem services
  • Sea-level rise can also cause the loss of valuable coastal ecosystems, such as mangroves, salt marshes etc.

 

How will sea-level rise affect societies?

• Increase in social disparities between people living in coastal areas
  • Rising sea level will cause changes in land cover. This land crunch will mean that those who are better off will be able to cope better than marginalised groups.
• Affect the livelihoods of the coastal communities
  • Since the lives of coastal communities, including their economic activities, is tied intricately with the coastal ecosystem.
  • Hence, changes in the coastal ecosystem as a result of GSML rise will further endanger the socio-economic stability of these communities.

 

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Q1) What is cryosphere?

The cryosphere refers to the parts of the Earth's surface where water is in solid form, including snow, ice caps, glaciers, permafrost, and sea ice. This term is used to describe the frozen water that covers a significant portion of the planet's surface and plays a crucial role in regulating the Earth's climate and global water cycle. The cryosphere is highly sensitive to changes in temperature and other environmental factors, and changes in the cryosphere can have significant impacts on ecosystems, sea level, and weather patterns.

 

Q2) What is coastal erosion?

Coastal erosion is the natural process by which the land along a coastline is gradually worn away by the action of wind, waves, tides, and currents. This process is driven by natural forces such as storm surges, wave action, and rising sea levels. Coastal erosion can also be caused by human activities such as construction, dredging, and the removal of vegetation that stabilizes coastal soils.

 

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Source: Explained | How rising sea levels threaten agriculture, rainfall, and the social fabric | WMO | The Hindu