A reduced AMOC is projected to bring colder weather overall to the UK and northern Europe, with much more intense winters and storms off the Atlantic, as well as reduced summer rainfall and crop productivity and a greater likelihood of extreme weather events such as the 2015 European summer heatwave. The impacts are not limited to this side of the Atlantic either. Increased sea levels are predicted on the US eastern seaboard, with the associated increased risks of flooding and potentially increased hurricane intensities.
Such large changes in ocean circulation also put the ecosystems and aquaculture we depend upon at risk. Marine deoxygenation and changes in key species abundances have been linked to an AMOC slowdown, along with an overall reduction in North Atlantic ocean productivity.
The far southern end of the AMOC around Antarctica is also of concern. The global ocean as a whole has absorbed more than 90% of human induced warming, absolutely dwarfing the changes in air temperature that we are all so concerned with. The vast ocean ringing Antarctica is where most of this extra heat (and carbon dioxide) has been injected into the deep ocean, and it is warming and acidifying at an alarming rate. One of the main areas of research for oceanographers such as myself is whether the ocean will continue to essentially sweep human impacts under the carpet – and what may happen if that stops.
This should not be a cause for despair and inaction though. The same models that predict the AMOC slowdown also show that strong emission reductions now can drive an AMOC recovery towards the end of the century. Research may reduce uncertainties, but the message is clear: strong climate action at governmental and industrial levels is needed now, and it is the job of the people to force such action with their wallets and votes.