Sea-rise data a wake-up call for coast

Brooks Harrison of Charleston looks out the door to Eastside Soul Food where he works as tidal flooding covered many downtown streets in October in Charleston. “Can’t do business in the middle of this ocean,” he said wondering when he would be able to open the store.

The sea is rising faster than it has in 28 centuries. We’re causing it with carbon emissions. And it could mean the virtual loss of the Lowcountry coastal community.

The strength of the spike in sea rise and the link with climate warming surprised even the researchers who expected to find some connection in a landmark study released this week. Co-author Ben Horton, a marine and coastal science professor at Rutgers University, makes no bones about it.

“This is the first study to produce a record stretching over nearly 3,000 years,” he said. “We can show the rate of sea level rise in the 20th century is faster than anything we’ve seen (in 2,800 years) everywhere along the East Coast, including your state.”

Because of that and the parallels in rise and fall of global temperatures and seas across the millennia, “We can say conclusively that carbon emissions produced by man are primarily responsible (in South Carolina) for beach retreat, coastal flooding and aquifer intrusion,” he said.

“We are living in very unusual times. If we don’t do anything about greenhouse gases, sea rise will exceed one meter (3 feet) by 2100 and you will have to make very, very difficult decisions about coastal management or retreat,” he said. “If we do something about it, potentially the coasts can continue to prosper.”

Scott Harris, College of Charleston geologist, characterized the study as “well done, well documented, with a well-vetted data set, by a very large group of people who are respected worldwide.” He called it a wake-up call for coastal and state leaders.

“Let’s just look at the data,” putting politics aside, he said. “The data are quite clear. In Charleston, in particular, we are in a very tough situation.”

The exhaustive study drops with a decisive thud among a ream of observed phenomena and previous studies suggesting or indicating the same conclusion. Among them:

A 2014 National Oceanic and Atmospheric Administration study concluded that Charleston floods four times more often today than it did in the 1960s, and it’s going to get worse. A number of factors were cited, including the loss of natural barriers, such as wetlands, as well as sea-level rise and land subsidence.

Higher seas have begun to wash away the salt marshes, a nightmare scenario of sea rise in the Lowcountry. The losses have been so severe in the Cape Romain National Wildlife Refuge that officials there are looking to buy properties closer to shore and just inland to try to replace the protected habitats.

Charleston already has broken the annual record for nuisance, or extreme, flood days for a period measured from May to April (spring tides to spring tides), said William Sweet, NOAA oceanographer. So far, there have been 37 days with nuisance tidal flooding for the 2015 period ending in April 2016. The historical record, 35 days, was set in 2013. In 2014, there were 33 days.

The study takes note of the contrast in Charleston, which experienced 34 days of tidal flooding from 1955 to 1964, then 219 days between 2005 and 2014.

The increase in flooding means that over the next decade or two, more sea walls will be needed, more beach and shoreline renourishment. Every spot protected might well mean the one next door erodes quicker. The list is expected to keep growing and the millions of dollars in costs piling up.

If sea rise overwhelms the barrier islands, a 10-foot scarp at the land edge of the marshes will become the next coast. It’s the upland boundary inland along Mount Pleasant and James Island, the point where the land drops steeply to the marsh.

Horton said the 28 centuries of data in the study allow researchers to develop a model to determine exactly how much sea rise is attributable to human sources, answering a question repeatedly raised by skeptics who claim the rise is largely natural. And it will allow them to accurately assess future consequences of various levels of warming.

“It portrays the stark contrasts of the realities we’re facing,” he said.

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