Atlantic Meridional Overturning Circulation

Last Updated09/08/2021

According to a study published in the journal Nature Climate Change, the Atlantic Meridional Overturning Circulation (AMOC) is losing its stability.
It has implications for the entire planet's weather systems is showing signs of instability due to human-made climate change,
Its collapse would have dire consequences for our weather and life on Earth.

The Atlantic Meridional Overturning Circulation (AMOC) is a large system of ocean currents that transports warm water from the tropics northwards into the North Atlantic.
It is the Atlantic branch of the ocean conveyor belt or Thermohaline circulation (THC).
AMOC carries warm surface waters from the tropics towards the Northern Hemisphere, where it cools and sinks, 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.
It then returns to the tropics and then to the South Atlantic as a bottom current.
From there it is distributed to all ocean basins via the Antarctic circumpolar current.

Gulf Stream, a part of the AMOC, is a warm current responsible for mild climate at the Eastern coast of North America as well as Europe.
Without a proper AMOC and Gulf Stream, Europe will be very cold.
Modelling studies have shown that an AMOC shutdown would cool the northern hemisphere and decrease rainfall over Europe.
It can also have an effect on El Nino.
Sea ice can increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic.
Freshwater from melting Greenland ice sheets and the Arctic region can make circulation weaker as it is not as dense as salt water and doesn’t sink to the bottom.

decrease in marine productivity in the North Atlantic (less sinking will lead to less mixing of water),
more storms in Northern Europe,
less Sahelian summer rainfall and South Asian summer rainfall,
a reduced number of tropical cyclones in the Atlantic
an increase in regional sea level along the northeast coast of North America.

Global warming can cause a weakening of the major ocean systems of the world.
The freshwater from the melting ice reduces the salinity and density of the water. Now, the water is unable to sink as it used to and weakens the AMOC flow.
As the Indian Ocean warms faster and faster, it increases precipitation.
With so much precipitation in the Indian Ocean, there will be less precipitation in the Atlantic Ocean, leading to higher salinity in the waters of the tropical portion of the Atlantic.
This saltier water in the Atlantic, as it comes north via AMOC, will get cold much quicker than usual and sink faster.****