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,
  • record rainfall in Pakistan, and unprecedented heatwaves that struck Europe and China in 2022.

What’s in today’s article?

• 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.
• 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.
  • Sea-level rise may force millions of people living in low-lying coastal areas to relocate to safer areas.
• 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.
• 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.