Flooding along the US Northeast coast has increased exponentially as a crucial web of Atlantic Ocean currents falters, a new study finds — a ominous preview of things to come as some experts suggest the present system may be on the brink of collapse in mere decades.
The Atlantic Meridional Overturning Circulation, or AMOC, is a giant conveyor belt that transports heat, salt and freshwater across the ocean and has climate, weather and sea level implications globally.
Rising sea levels caused by global warming is the major cause of coastal flooding, but the AMOC is also at fault since it plays a significant role in the Northeast, according to a new study published Friday in the American Association for the Advancement of Science.
Scientists used tide gauge observations — instruments recording sea level rise — and complex models of the ocean to estimate the extent to which the AMOC has contributed to flooding in recent decades.
They discovered from 2005 to 2022, up to 50% of flooding on the northeastern coast was caused by a weaker AMOC. In simpler terms, sea level rise caused by AMOC generated up to eight days of flood a year for that duration. The researchers’ models also give an early look at what is in store so that they can forecast frequency of coastal flooding in the Northeast three years down the road, the study says.
The idea that the AMOC is affecting sea level rise here is not new, but this study is the first to conclude it’s having a significant effect on the rate of flooding, said Liping Zhang, co-author of the study and project scientist at the Geophysical Fluid Dynamics Laboratory, which is a National Oceanic and Atmospheric Administration laboratory.
There are two main reasons why the AMOC impacts sea level rise, said David Thornally, University College London professor of ocean and climate science, not involved with the study.
A robust AMOC is generally linked to dense deep water that flows along the western boundary of the North Atlantic. As the AMOC declines, water is less dense, literally occupying more space and driving sea level rise. A weaker AMOC also impacts the northward motion of the Gulf Stream, and water will move onto the coastal shelf, adding to sea level rise near the coast. Sea level rise is a mammoth and urgent issue to mankind as the world warms up, and the more we know about how it’s being affected, the better, Zhang told CNN. Coastal flooding can “reshape the coastal environment… (and) puts both lives and infrastructure in coastal areas at risk,” she added.