Rising sea levels: Is global warming making the US East Coast a 'hot spot?' (+video)
The pace of sea-level rise along much of the East Coast is accelerating three to four times faster than the worldwide average, a US Geological Survey study says. Global warming is the chief suspect.
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The team posits that a key difference between its study and the one published in 2011 is that the 76 percent of the tide gauge data used in the previous study goes so far back – when little or nothing was happening – that they inadvertently skewed the results toward little or no change.Skip to next paragraph
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The results imply that New York City could see at least an extra 20- to 29-centimeter (7.9- to 11.4-inch) rise in sea levels by 2100 above the heightened global average at the time.
The study by Sallenger's team, published Sunday in the journal Nature Climate Change, follows a report from the National Research Council projecting as much as a four to five foot rise in sea levels along the US West Coast by 2100.
That study, requested by the State of California to inform its adaptation plans, as well as the USGS study, underscore changes in local sea levels that global averages can mask. The factors that can alter the local picture range from subsidence – as people draw down aquifers along the coast or as they drain and develop marshlands – to changes in the distribution of Earth's gravity as ice caps melt and add their water to the oceans.
Even Earth's restless tectonic plates get into the act. The NRC study suggests that sea levels in the Pacific Northwest might fall slightly during the first part of this century relative to the coast because the land is being pushed upward by movement along the subduction zone marking the western edge of the Juan de Fuca plate offshore. At least in the near-term, the uplift could outpace sea-level rise.
The US East Coast isn’t the only US coastline hosting a sea-level hot spot. Southern Louisiana is another one, although for a different mix of reasons. There, over the past century, sea level has risen at a pace of about 10 mm a year. But sea-level rise, measured at Pensacola, Fla., is occurring at 1.65 mm a year, according to a recent study by researchers at Tulane University, at a location where the land isn't subsiding. Thus, for the Mississippi Delta the global-warming component to sea level rise, while important, has been outpaced by subsidence.
Along the East Coast's hot spot, by contrast, the team's measurements suggest that subsidence isn't a significant player in the acceleration it found. The pace is most consistent with the slowing of Atlantic currents along the coast, either from warming waters, melting ice, or some combination, Sallenger says.
The take-home messages, he says: “Acceleration is indeed happening within the United States and can be seen in data,” and sea-level rise does not manifest itself the same way everywhere; it's not like filling a bathtub.
“Rather, it varies over regional scales,” he adds.