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Model suggests impact of global warming on AMOC has led to increased flooding along US Northeast Coast

A team of geophysicists and atmospheric scientists at Princeton's NOAA/Geophysical Fluid Dynamics Laboratory and the University of Maryland Center for Environmental Science has found evidence that a warming planet over the past 15 to 20 years has impacted the Atlantic Meridional Overturning Circulation (AMOC) and led to an increase in the number of flooding events along parts of the U.S. Northeast Coast (USNEC).

In their study in the journal Science Advances, the group created a model to make estimates regarding the number of flooding events along the USNEC that would have occurred if not for global warming over the past decades and how it differed from reality.

The AMOC is a mammoth network of currents that interact in the Atlantic Ocean, including the Gulf Stream. Its net effect is to move warm water near the surface in a northerly direction and deeper, colder water in a southerly direction. Circulation happens as warm water from the tropics makes its way north and mixes with cold meltwater from the northern latitudes, causing it to sink. Prior research has suggested that as the planet warms, the AMOC is being weakened as more meltwater flows into the sea.

To learn more about changes wrought by a weakening AMOC and associated sea level rise, the research team began by using an existing model to simulate ocean dynamics in the Atlantic Ocean. They then fed that same model tidal map data for the years 1912 to 2022, forcing it to conform to actual real-world conditions. Next, they adjusted the resolution to focus their efforts on changes along the eastern coastal region in the U.S.

Doing so allowed them to make estimates regarding the number of flooding events along the USNEC that should have occurred over the years 2005 to 2022 had conditions remained as they were prior to changes to the AMOC. They then compared their estimates with the number of flooding events that actually occurred along the USNEC, and found differences ranging from 20% to 50%.

The researchers suggest that global warming has a major impact on the AMOC that will likely continue. The findings may enable them to predict flooding up to three years in advance. They further note that their model did not include changes in the future due to continued ice melt, which likely means the region could see even more flooding events than the model predicted.