North Carolina researchers track risk from rising sea level

Insurance Journal: …Scientists at the Renaissance Computing Institute (RENCI) and the University of North Carolina at Chapel Hill use the latest modeling techniques and high performance computing power to understand how expected increases in sea level over the next 100 years could affect coastal communities, wildlife and the coastline itself. RENCI, launched in 2004, is a collaborative institute involving the University of North Carolina at Chapel Hill, Duke University and North Carolina State University.

Most scientists believe that melt water from glaciers, the Greenland ice sheet and possibly the West Antarctic ice sheet, along with thermal expansion from warming oceans, will raise sea levels by 1.6 to 3.2 feet over the next century and by 6.5 feet over the next 200 years. If that happens, North Carolina’s coast will change dramatically by 2100 or 2200, according to Tom Shay, a UNC-Chapel Hill marine scientist who conducts research with the UNC Institute for the Environment, the UNC department of marine sciences and UNC’s Center for the Study of Natural Hazards and Disasters.

“Some areas of the Outer Banks are only a few meters above sea level now, and there will be an increased tidal range and larger areas inundated by tides,” said Shay. With deeper water in the sounds, storm wave heights would increase as well, he said.

…Shay uses the coastal storm surge modeling software and the SWAN (for Simulating WAves Nearshore) wave modeling software to create new “What If” models, showing how a major storm could affect the coast if sea levels were higher. The work complements work done at RENCI. The Federal Emergency Management Agency (FEMA) uses the RENCI model output to develop new flood insurance rate maps for coastal North Carolina.

Shay’s work zeroes in on one storm: Isabel, which made landfall in North Carolina in 2003 as a Category 2 hurricane. Using data on coastal topography and bathymetry compiled for the floodplain mapping modeling effort, Shay models the storm at current sea levels and at sea levels ranging from .5 to 2 meters higher. Although his simulations show more pronounced storm surge and flooding during the hypothetical Hurricane Isabels, Shay stressed that the results depict a possible future, not a certainty.

“There are a lot of unknowns and uncertainties,” he said. “A warming ocean will cause some sea level rise just because of thermal expansion, but we don’t know how fast the ocean will warm or how fast the Greenland ice will melt or whether the West Antarctic ice sheet will melt. All those things have a range of possible outcomes and we want to understand as many of the possible outcomes as we can.”…