Sea levels between New York and Newfoundland rose by about 10cm in 2009 and 2010 because ocean circulation changed, according to a report in the journal Nature Communications.
The event, independent of hurricanes or winter storms, caused flooding along the northeast coast of North America.
A team from the University of Arizona-led was the first to document that the extreme increase in sea level lasted two years and not just a few months.
“The thing that stands out is the time extent of this event as well as the spatial extent of the event,” said Paul Goddard, a doctoral candidate in geosciences.
The study of tide data back to 1900 is also the first to show the spike in sea level was caused by changes in ocean circulation.
The team found that, at the current rate of increase in atmospheric carbon dioxide, similar extreme events are likely to occur more frequently, Goddard said.
The research also confirmed that, as others have reported, sea level has been gradually rising since the 1920s.
The Atlantic Meridional Overturning Circulation had a 30% decline in strength in 2009-2010.
This ocean circulation system brings warm water from the tropics and the southern Atlantic Ocean to the North Atlantic and the polar regions. The water then cools and sinks, eventually flowing south in the deep ocean.
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