A North Carolinian is the U.S. watchman for rising seas. And he’s worried.
After I wrote recently about a new federal report on sea level rise, a reader pointed out to me that the report wasn’t just about the coast, it also has a tie to Raleigh.
The report’s lead author, William Sweet, grew up in Raleigh and vacationed as a youth on Topsail Island. A graduate of Sanderson High School, where he played for the soccer team in the early 1990s, Sweet went on to graduate from UNC-Chapel Hill and earn his master’s and his doctorate from N.C. State University.
Today Sweet, an oceanographer at the National Oceanic and Atmospheric Administration (NOAA), is the agency’s leading expert on sea level rise. He lives in Annapolis, Md., and explores the Chesapeake Bay, but he regularly ventures south to the Outer Banks and other barrier islands in North Carolina.
I spoke with Sweet this week about how a rising sea will affect North Carolina’s coast. His report estimates that the sea level along parts of the coast could rise as much as 14 inches by 2050.
“This is real, this is happening. It’s not an end-of-century issue any longer,” Sweet said. He hopes the data and maps provided by NOAA will spur coastal communities to take steps now to adjust to the change. “It doesn’t have to be a slow-motion disaster,” he said.
Beyond 2050, Sweet said, it’s unclear whether the rise in sea level will moderate or accelerate. It depends on the extent to which greenhouse gas emissions continue to heat the atmosphere, whether ice sheets in Greenland and Antarctica slide into the sea and how much seawater expands as it warms.
“It’s all conditioned ultimately by what humans do in terms of emissions and heating,” he said. “Unfortunately, you can’t just look into a crystal ball and say what the answer is going to be. But the takeaway is that less emissions equals less chance of overall higher sea level rise.”
The threat is obvious for the vulnerable Outer Banks, where tides are not only higher, but the islands themselves are moving toward the mainland. That dynamic speeds the collapse of beach homes into the encroaching sea and sends sand and rushing water over portions of U.S. Highway 12.
But the risk is not limited to the most vulnerable areas. Morehead City, Wilmington, Beaufort and other coastal North Carolina towns and cities are also seeing the effects. Rising sea levels are producing more flooding, even on sunny days. That backs up stormwater drains and makes septic systems malfunction and roads impassable. More serious flooding resulting from water rising three feet above high tide level now might occur once in several years, Sweet said, but by 2050 it could happen several times a year.
“The kind of flooding that can be problematic is definitely going to be fairly routine unless preventive measures are taken now to mitigate against those impacts,” he said. “That’s why we’re trying to provide the (flood) maps so folks can look and get a sense of what’s at risk.”
Some coastal geologists think the battle against the sea is already lost. New coastal development should end and people should accept that the sea that human activity has caused to rise will take its share of the shore.
Sweet takes a more moderate view: Coastal communities don’t need to retreat, but they will need to adjust.
For Sweet, the rise of the sea is not just about science. It’s also about the threat to places he knew in summers past, such as Topsail Island and other parts of the North Carolina coast.
“The barrier islands will move and erode and change,” he said. “In general it means as seas creep up, you’re going to have increased erosion, more permeation of the barrier island itself through groundwater and over-topping and back bay flooding. It’s just going to create more of a challenge to maintain the footprint in these shifting barrier islands, which Topsail is.”
Sweet added, “One thing is certain: Sea level is on the rise and unless some preventive upfront action is taken, the impact will grow in time.”
This story was originally published March 17, 2022 at 4:00 AM.