Atlantic Meridional Overturning Circulation (AMOC)

Why in News?

A recent study suggests that building a massive 50‑mile dam across the Bering Strait could, in theory, help stabilise the AMOC, a critical ocean current system that regulates global climate.

• AMOC – It is a massive system of ocean currents that moves warm water north and cold water south, acting like a “global conveyor belt.”
• It regulates climate by distributing heat and nutrients, but scientists warn it is weakening due to climate change, which could disrupt rainfall, raise sea levels, and cool Europe.
• Working
• Surface currents – It transports warm, salty surface water from the tropics toward Europe via the Gulf Stream and the North Atlantic Current.
• As it reaches Europe, it releases heat into the air and helps moderate the weather in Britain and the Nordic countries.
• Deep currents – In the process, the water cools, sinks in the Arctic, forming the North Atlantic Deep Water (NADW) and heads back southwards.
• It goes on to influence rainfall patterns in Africa, South America and beyond.
• Global link – These currents connect with the Antarctic Bottom Water (AABW) and circulate through the Indian and Pacific Oceans.

• Driving Forces – The system is driven by thermohaline circulation, which depends on differences in temperature & salinity of the water.
• Carbon & Nutrients – It plays a vital role in the global carbon cycle by sequestering carbon from the atmosphere into the deep ocean and circulating nutrients that support marine life.
• Disruption/Weakening due to Climate Change – The warming from greenhouse gases in the atmosphere is disrupting this system.
• Rising temperatures make the Arctic wetter.
• Greenland’s ice sheet melts, adding fresh water to the North Atlantic.
• This fresh water dilutes the saltiness, making the surface less dense.
• Without enough density, the water doesn’t sink properly, slowing the circulation, which in turn causes it to draw less warm water northward from the tropics.
• Impact of weakening of AMOC – If the AMOC were to stop completely -
  • Northern Europe would lose its warming influence and become much colder.
  • U.S. East Coast sea levels would rise as water shifts westward.
  • Tropical regions would see rainfall patterns change—some areas drying out, others flooding more.

References

1. Indian Express | Recent study published about weakening of AMOC
2. Britannica | AMOC
3. NOAA | AMOC