Why in the news?

  • A new study warns that the Atlantic Meridional Overturning Circulation (AMOC) could reach an irreversible tipping point within decades, with its collapse likely in 50–100 years.

Atlantic Meridional Overturning Circulation (AMOC)

  • What is it?
    • It is a large system of ocean currents in the Atlantic Ocean, part of the global Thermohaline Circulation (also called the “Global Conveyor Belt”).
    • AMOC transports warm, salty surface water northward and cold, deep water southward.
  • How it works?
    • Warm surface water flows from the tropics to the North Atlantic (e.g., Gulf Stream).
    • In the North Atlantic, the water cools and sinks due to increasing density (from cooling and salinity).
    • The cold, dense water flows southward at deep ocean levels.
    • Eventually, it upwells in the Southern Ocean and elsewhere, completing the circulation loop.
  • Importance of AMOC
    • Regulates climate in the North Atlantic region (e.g., Europe’s relatively mild winters).
    • Helps in carbon sequestration (draws down CO₂ into the deep ocean).
    • Supports marine ecosystems and fisheries by nutrient cycling.
    • Impacts monsoon systems including Indian and West African monsoons.
  • Evidence of Slowdown:
    • Scientific studies and IPCC reports indicate AMOC has weakened by ~15% since the mid-20th century.
    • May be at its weakest in over a millennium (based on proxy data).
  • Causes:
    • Global warming: Melting of Greenland ice adds freshwater, reducing salinity and density- disrupting the sinking process.
    • Increased precipitation and Arctic ice melt contribute to surface freshening.
  • Consequences:
    • Cooling in Europe, especially in Northwestern Europe.
    • Disruption of monsoons (especially Indian and Sahelian).
    • Sea-level rise along North American coasts.
    • Collapse of fisheries due to changes in nutrient upwelling.
    • Risk of a tipping point leading to abrupt climate changes.