Sea-level rise in 20th century was fastest in 2,000 years along much of East Coast

A recent study found that the rate of sea-level rise in the 20th century along much of the U.S. Atlantic coast was the fastest in 2,000 years. Roanoke Island, home of the East Carolina University Outer Banks Campus, was among six study sites.

According to the study published in the journal Nature Communications, the most significant change in the global sea-level rise rate occurred from 1900-2000, when it was more than double the average from years 0-1800. The total rate of sea-level rise for each of the six sites in the 20th century was 2.6 to 3.6 millimeters per year, or about 1 to 1.4 inches per decade. Two sites in southern New Jersey had the fastest rates of the six sites over the 2,000-year period, with both experiencing sea-level rise at more than half an inch per decade.

The study, the first to cover such an extensive time period, looked at the phenomena that contributed to sea-level change over 2,000 years along the coasts in Connecticut, New York City, New Jersey and North Carolina using a sea-level budget. A budget enhances understanding of the processes driving sea-level change. The processes are global, regional (including geological, such as land subsidence) and local, such as groundwater withdrawal.

“Coastal communities across the globe are having to make some tough decisions related to sea level rise. This study shows the significance of the challenge along much of the East Coast of the U.S.  …. We have been experiencing the highest rates of sea-level rise during the last century relative to the last 2,000 years — significantly higher rates, and that isn’t going to change moving forward,” said co-author Reide Corbett, dean of ECU’s Integrated Coastal Programs and executive director of the Coastal Studies Institute on the ECU Outer Banks Campus.

“This study provides a better understanding of the sources, the processes that have led to that increase in rate of sea-level rise. It’s science like this, a collaborative approach to understanding our coastal challenges, that can help provide the information needed to make informed decisions and develop sound policies necessary to respond effectively to climate change along our coasts.”

Sea-level rise stemming from climate change threatens to permanently inundate low-lying islands, cities and lands, and heightens their vulnerability to flooding and damage from coastal and other storms.

While most sea-level budget studies are global and limited to the 20th and 21st centuries, the team of researchers, which included Corbett, estimated sea-level budgets for longer timeframes over 2,000 years. The goal was to better understand how the coastal processes driving rising sea levels have changed and could continue to change in the future. The methods used could prove helpful for sites around the world. The broader understanding of drivers and the practical application of methods are imperative for informing regional and local decision-makers when it comes to planning and responding to sea-level rise.

Using a statistical model, scientists developed sea-level budgets for six sites, dividing sea-level records into global, regional and local components. They found that regional land subsidence — sinking of the land since the Laurentide ice sheet retreated thousands of years ago — dominated each site’s budget over the last 2,000 years. Other regional factors, such as ocean dynamics, and site-specific local processes, such as groundwater withdrawal that helps cause land to sink, contributed much less to each budget and vary over time and by location.

Other contributors to the study include lead author Jennifer S. Walker and others from Rutgers University – New Brunswick, as well as scientists at Nanyang Technological University, Maynooth University, The University of Hong Kong, Bryn Mawr College, Durham University and Liverpool Hope University.

For more information read the study at nature.com.

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Contact: John McCord, UNC Coastal Studies Institute, mccordr@ecu.edu

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