A handful of scientists and engineers tasked with providing a reasonable estimate of sea level rise on North Carolina’s coast over the next 30 years are still discussing ways to interpret data variances as an internal deadline for the first draft of a report looms.
The N.C. Coastal Resources Commission Science Panel is not conducting new modeling for the report, instead relying on existing data, mostly from tide gauges operating for different periods of time at locations along the coast.
Existing data does not immediately suggest a linear rate of sea level rise, so the panel must also determine how other factors, like varying rates of land subsidence and ocean currents, skew the numbers.
One method presented by panel member Tom Jarrett, a Wilmington-based engineer who retired from the U.S. Army Corps of Engineers, examines the relationship between long-term data and short-term data to produce a modest rate of sea level rise over the last century.
Jarrett estimated sea level rise of 1.02 feet per 100 years in Duck, N.C., compared to 0.62 feet per 100 years in Wilmington.
“I felt that my input could provide a reality check with all these things that people are saying could happen, might happen. It all depends. The base of it is what’s gone on in the past and how you interpret that,” Jarrett said during a Sept. 30 phone interview.
Jarrett studied data collected over longer periods of time in Sewells Point, Va., Wilmington, and Charleston, S.C., and short-term data collected in Duck, the Cape Hatteras Fishing Pier, Morehead City and the Springmaid Pier south of Myrtle Beach, S.C.
After observing similar up-and-down patterns among data collected from the gauges, Jarrett created a ratio to find long-term estimates for locations with less historical data.
Jarrett also tried to isolate the rise of ocean waters from other factors causing the data to oscillate.
“The fluctuations are quite large,” Jarrett said. “All of that stuff is occurring at the same time that the sea is gradually creeping up, so in any one time period, the fluctuations in sea level can overwhelm any long-term rate.”
Jarrett stressed that his estimates were only one way of analyzing the data. He said the panel plans to provide a range of estimates in the final report.
Other methods, proposed by panel members Greg Rudolph and Beth Sciaudone, would use global data collected by the Intergovernmental Panel on Climate Change and local land movement data to project reasonable ranges.
The panel did not determine which method will be used for the report during the Sept. 24 meeting.
A first draft of the updated report is expected to be complete by Oct. 24 to allow the panel time to review and revise the report internally before passing it to Dr. Robert Dean, professor emeritus in University of Florida’s coastal and oceanographic engineering program, and Dr. James Houston, retired Corps engineer, for peer review.
A final draft is due to the Coastal Resources Commission by Dec. 31. The report will be available for public comment by March 31, 2015, and after an extended public comment period, it will be submitted to the General Assembly by March 2016.
The public is invited to participate in the process before the report is finalized by attending science panel meetings, or by submitting comments or research for the panel to consider. Tancred Miller, coastal policy manager for the N.C. Division of Coastal Management, said the same handful of people have participated so far.
“We have sort of a following. Pretty much the same couple folks have been giving us comments at every meeting,” Miller said during a Sept. 29 phone interview.
The date of the next meeting is tentatively set for Oct. 20, but Miller said the meeting might move to Oct. 24. Meetings are held in New Bern, a central location for panel members spread from north to south.
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