A 2-year spike in sea level along NE North America

Coastal floodingA 2-year spike in sea level along NE North America
Published 26 February 2015

Sea levels from New York to Newfoundland jumped up about four inches in 2009 and 2010 because ocean circulation changed, new research has found. Independent of any hurricanes or winter storms, the event – which stands out in its time extent as well as its spatial extent — caused flooding along the northeast coast of North America. Some of the sea level rise and the resulting flooding extended as far south as Cape Hatteras. The spike was the result of a change in the ocean’s Atlantic Meridional Overturning Circulation and also a change in part of the climate system known as the North Atlantic Oscillation. The researchers found that at the current rate that atmospheric carbon dioxide is increasing, such extreme events are likely to occur more frequently. The research also confirmed that, as others have reported, sea level has been gradually rising since the 1920s and that there is some year-to-year variation.

Sea levels from New York to Newfoundland jumped up about four inches in 2009 and 2010 because ocean circulation changed, a University of Arizona-led team reports in the recent issue of Nature Communications.
The team was the first to document that the extreme increase in sea level lasted two years, 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 first author Paul Goddard, a UA doctoral candidate in geosciences.
A UA release reports that independent of any hurricanes or winter storms, the event caused flooding along the northeast coast of North America. Some of the sea level rise and the resulting flooding extended as far south as Cape Hatteras.
The paper is also the first to show that the unusual spike in sea level was a result of changes in ocean circulation.
Co-author Jianjun Yin, UA assistant professor of geosciences, said, “We are the first to establish the extreme sea level rise event and its connection with ocean circulation.”
Goddard detected the two-year-long spike in sea level by reviewing monthly tide-gauge records, some of which went back to the early 1900s, for the entire Eastern Seaboard. No other two-year period from those records showed such a marked increase.
The team linked the spike to a change in the ocean’s Atlantic Meridional Overturning Circulation and also a change in part of the climate system known as the North Atlantic Oscillation. The researchers then used computer climate models to project the probability of future spikes in sea level.
The team found that, at the current rate that atmospheric carbon dioxide is increasing, such extreme events are likely to occur more frequently, Goddard said.
Goddard’s and Yin’s research paper is titled “An Extreme Event of Sea Level Rise along the Northeast Coast of North America in 2009-10.” Stephen Griffies and Shaoqing Zhang of the National Oceanographic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, are also co-authors. NOAA funded the research.
Yin’s previous work on climate models suggests that weakening of the Atlantic Meridional Overturning Circulation could cause sea levels to rise faster along the northeast coast of North America.

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