What is Atlantic Meridional Overturning Circulation (AMOC)? Discuss the reasons for recent decline in the AMOC and its associated impact.

Atlantic Meridional Overturning Circulation is a phenomenon of large ocean current circulation in the Atlantic Ocean, that redistributes heat, salinity, etc., between parts of the ocean, as below.

  • Warm north Atlantic current takes warm waters towards coast of Norway, heating surrounding coasts.
  • A branch of this warm current, flows along coast of western Europe.
  • Cold current flows along north American coast southwards, completing circulation.
  • Cold water along north Atlantic cools down and sinks to bottom and flows south.

Reasons for recent decline in AMOC:

  • Melting of glaciers – freshwater from Greenland, Iceland, etc, reduces salinity of water, which slows down sinking and circulation.
  • Global warming – weakens cooling of oceans by circulation.

Impacts of decline:

  • On climate: Enhanced extremes of temperature along Norwegian Coast.
  • Livelihood: Decline in fishing & fishing & another ocean livelihood along north Atlantic coast.
  • Impact on Biodiversity: Marine biodiversity has a narrow range of temperature habitability so there is a threat of loss of biodiversity due to AMOC changes.
  • Impact on Indian monsoons: AMOC is associated with monsoonal winds over south asia. Decline in AMOC will impact rainfall over India.

Thus, AMOC has far reaching impacts on marine & terrestrial ecosystems.

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