WASHINGTON – Several years ago, in 2009 and 2010, a string of unexplained floods and unusually high tides struck the East Coast.
There was no easy explanation. No hurricane. No winter storm. But the waters kept spilling across the shoreline, from North Carolina’s Cape Hatteras to Canada.
The cause of that phenomenon may now have finally been found. Sea levels from New York to Newfoundland were undergoing an “extreme” surge unlike any other in recorded history, according to a new study in Nature Communications published this week.
Calling the phenomenon “unprecedented” and “very unusual,” the Atlantic Ocean along the East Coast rose roughly 4 inches between 2009 and 2010 in a rapid spike researchers compared to a “1-in-850 year event.”
“This is a very extreme event,” Jianjun Yin of the University of Arizona told the Washington Post in a phone interview.
“The sea level has since dropped after that spike, but it is still much higher than it was when the spike began in 2009. . . . Global warming definitely contributed to this event.”
But global warming wasn’t the sole culprit.
The study suggested a change in ocean currents coupled with persistent winds that pushed water into the region caused the spike – which may be the first of many. The seas are rising, Yin told the Post, but the ascent isn’t smooth or even.
The mechanics of sea rise aren’t dissimilar to temperatures rising during spring. During some years, the weather gets warmer faster –” but the general trend is upward.
“We should expect more of these extreme rises in sea level,” lead author Paul Goddard said. “And for this to happen more in the future.”
Yin has long studied how ocean currents affect sea levels. He developed a hypothesis involving a major current in the Atlantic Ocean called the Atlantic meridional overturning circulation.
He said a slowing of that current would lead to higher tides along the East Coast. The current transports warmer water from the tropics to the waters of the North Atlantic and polar regions.
Once there, the water cools, sinks, and is then transported back to the tropics through the deep ocean in a system that works like a conveyor belt.
As the science website LiveScience explained, “the water temperature differences drive the current.”
But then in 2009 and 2010, a wrench was thrown into the system with warmer-than-average water temperatures in the North Atlantic’s Labrador Sea.
Recent research, the scientists noted, showed the warm water perhaps decreased the strength of the current by as much as 30 percent.
“The anomalous heat made the surface waters less dense and less likely to sink, and it created a bottleneck” of water along the Eastern seaboard, Goddard told LiveScience.