'The Atlantic Meridional Overturning Circulation (
AMOC) is a large system of ocean currents that transfers warm salty water northward. This water cools on its winding journey north, which makes it denser. As the cold water sinks, water from other oceans is pulled in to fill the surface, driving the circulatory system back down south again.
AMOC has been
slowing down significantly since the mid-1900s.
With increasing contributions of freshwater from melting glaciers and greater rain, concentrations of salt in the sea water drop, and the saline water becomes less dense, disrupting the sinking process and weakening the entire physical cycle.
...
AMOC has only been directly monitored since 2004, so it has not been long enough to understand the full trajectory of the current slowing trend. As a result, scientists have been using indirect indicators like salinity levels to try and fill in their knowledge gaps.
Van Westen and team have yet to amalgamate all the factors to accurately predict when the AMOC collapse will occur, but they believe that catastrophic moment is a lot closer than many current simulations suggest.
...
Collapse of the AMOC
happens cyclically over a million-year scale, and based on past occurrences, we know the Arctic should extend south during this time, leading to decreased temperatures in northwestern Europe by up to 15 °C,
disrupting tropical monsoons and heating up the Southern Hemisphere even further.'
It's Confirmed. A Major Atlantic Ocean Current Is Verging on Collapse. - Science Alert