A recent paper in Nature Communications “Warning of a forthcoming collapse of the Atlantic meridional overturning circulation” predicts a major change for the North Atlantic Ocean circulation between 2025 and 2095. The scientists who wrote this paper, Peter Ditlevsen and Susanne Ditlevsen, have used new modeling to predict the shutdown of what is known as the Atlantic meridional overturning circulation (AMOC). Previous estimates had predicted this shutdown to occur in the 22nd century, but this new study does a better job of picking out early warning signals from noise in the data to provide a more accurate prediction of this change.
The AMOC is a strong driver of Earth’s ocean currents. As warm waters from the North Atlantic Current (part of the Gulf Stream) cool near Greenland and salinity increases due to a variety of factors, the cold salty water sinks deep into the ocean. This sinking of cold salty water pulls warm surface water northward and drives deep cold salty water southward in a giant convection current.
Global warming is disrupting the AMOC primarily through increased Greenland glacier melting which increases the amount of fresh water in the northern Atlantic Ocean. As high salt content in water makes it much denser, fresh water mixing with the North Atlantic water decreases the density and prevents the water from sinking as it normally would.
Disruption of the AMOC’s sinking cold water would cause immense climate change throughout the globe. Weather patterns around the world would become more variable as a set of cascading changes of ocean currents significantly and quickly change the conditions driving local weather patterns. For example, without a strong Gulf Stream bringing warm water and air north, Europe will see a major shift in climate, potentially becoming dryer and colder. North America would see a significant sea level rise, and North Atlantic storms would become more severe. Even areas on the far side of the globe would see changes as the currents eventually rewrote themselves.
This study assumes current policies are maintained. Which means that by aggressively pursuing policies to reduce green house gases like CO2 and methane we would be able to stall or even prevent a shutdown of the AMOC. We can accomplish these reductions if we as a society summon the will and political power to put them in place over the objections of greedy individuals and corporations.
My apologies for brevity, typos, and a greatly reduced ability to respond to comments as I am traveling and have limited time available. I’m literally losing sleep in order to find the time to write on this topic because it is so important for everyone to do their part.