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Concerning the Atlantic Meridional Overturning Current (AMOC)

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Context:

Scientists have been worried by signs that AMOC may be slowing, which could have drastic consequences on global climate, data showing for the past 15 years.

Background:

  • A new study suggests that AMOC is getting help from the Indian Ocean.
  • Warming as a result of climate change, the Indian Ocean is causing a series of cascading effects that is providing AMOC a jump start.

Atlantic Meridional Overturning Current (AMOC):

  • In the Atlantic operates a large system of ocean currents, circulating the waters between the north and the south called Atlantic Meridional Overturning Current, or AMOC, it ensures the oceans are continually mixed, and heat and energy are distributed around Earth.

Working of Atlantic Meridional Overturning Current (AMOC):

  • The phenomena act as a conveyor belt process.
  • As warm water flows northwards in the Atlantic, it cools, while evaporation increases its salt content.
  • Low temperature and a high salt content raise the density of the water, causing it to sink deep into the ocean.
  • The cold, dense water deep below slowly spreads southward.
  • Eventually, it gets pulled back to the surface and warms again, and the circulation is complete.
  • This continual mixing of the oceans, and distribution of heat and energy around the planet, contribute to global climate.

Other such alternative system:

El Nino-Southern Oscillation (ENSO):

  • This involves temperature changes of 1°-3°C in the central and eastern tropical Pacific Ocean, over periods between three and seven years.
  • El Niño refers to warming of the ocean surface and La Niña to cooling, while “Neutral” is between these extremes.
  • This alternating pattern affects rainfall distribution in the tropics and can have a strong influence on weather in other parts of the world.

Indian Ocean Dipole (IOD):

  • It involves an aperiodic oscillation of sea-surface temperatures (SST), between positive, neutral and negative phases.
  • A positive phase sees greater-than-average sea-surface temperatures and greater precipitation in the western Indian Ocean region, with a corresponding cooling of waters in the eastern Indian Ocean which tends to cause droughts in adjacent land areas of Indonesia and Australia.
  • The negative phase of the IOD brings about the opposite conditions, with warmer water and greater precipitation in the eastern Indian Ocean, and cooler and drier conditions in the west.

Concerns associated:

  • AMOC has been stable for thousands of years but data since 2004, as well as projections, have given some scientists cause for concern.
  • Whether the signs of slowing in AMOC are a result of global warming or only a short-term anomaly is to be researched.
  • AMOC had weakened substantially 17,000 to 15,000 years ago, and it had global impacts.
  • Warming in the Indian Ocean as it is one of the fingerprints of global warming would act as a jump start for AMOC, intensifying the circulation.
  • If other tropical oceans’ warming, especially the Pacific, catches up with the Indian Ocean, the advantage for AMOC will stop.
  • It can have dramatic consequences for Europe and other parts of the Atlantic rim.

How Indian Ocean affects the AMOC:

  • As the Indian Ocean warms faster and faster, it generates additional precipitation.
  • This draws more air from other parts of the world to the Indian Ocean, including the Atlantic.
  • With so much precipitation in the Indian Ocean, there will be less precipitation in the Atlantic Ocean.
  • Less precipitation will lead to higher salinity in the waters of the tropical portion of the Atlantic because there won’t be as much rainwater to dilute it.
  • This saltier water in the Atlantic, as it comes north via AMOC, will get cold much quicker than usual and sink faster.

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