U.S. Coastal Sea-Levels Are Rising At An Accelerated Rate

sea-level rise
Sea-level report cards display recent sea-level trends and project sea-level height to the year 2050. Source: Virginia Institute of Marine Science

Coastal sea levels in the U.S. are rising—and at an accelerating rate, according to the latest “report card” by researchers at William & Mary’s Virginia Institute of Marine Science. The team’s annual web-based report analyzes tide-gauge records for 32 localities along the U.S. coast from Maine to Alaska.

“The key message from the 2019 report cards is a clear trend toward acceleration in rates of sea-level rise at 25 of our 32 tide-gauge stations. Acceleration can be a game changer in terms of impacts and planning, so we really need to pay heed to these patterns,” says project founder, VIMS emeritus professor John Boon.

Last year, rates of sea-level rise accelerated at all 21 of the report-card stations along the U.S. East and Gulf coasts, and at seven of the eight monitored stations along the U.S. West Coast, excluding Alaska. All four stations monitored in Alaska show relative sea level falling at increasingly rapid rates, where the continued rise of coastal mountains generates sharp decreases in sea level relative to land. The relative sea-level rise in Virginia and other East and Gulf coast areas is due to both rising water and sinking land.

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An amphibious shed rises with floodwaters in the VIMS Boat Basin. Photo by VIMS.

VIMS marine scientist Molly Mitchell says “seeing acceleration at so many of our stations suggests that—when we look at the multiple sea-level scenarios that NOAA puts out based on global models—we may be moving towards the higher projections.” She adds, “We have increasing evidence from the tide-gauge records that these higher sea-level curves need to be seriously considered in resilience-planning efforts.”

Previous work by Boon, Mitchell, and VIMS colleague Derek Loftis suggests the current acceleration in rates of sea-level rise began around 2013 or 2014, likely associated with ocean dynamics and ice-sheet loss. “Although sea level has been rising very slowly along the West Coast,” says Mitchell, “models have been predicting that it will start to rise faster. The report cards from the past three years support this idea.”

Notable 2019 findings

The three highest rates of sea-level rise in 2019 occurred along the Gulf Coast at: Grand Isle, LA; and Rockport and Galveston, TX. Rockport also topped all 32 stations in its rate of acceleration. Grand Isle and Galveston showed significant but much more moderate acceleration rates in 2019.

After Rockport, the highest rates of acceleration in 2019 were observed at: Pensacola, FL and Wilmington, NC; Cedar Key, FL; Eastport, ME; Naples, FL; Boston, MA; Portland, ME; Charleston, SC; and Port Isabel, TX. Significant acceleration in rates of sea-level rise at these widely distributed localities hints at global drivers, with climate change the obvious suspect. NOAA recently reported that 2019 was the second warmest year in recorded history.

The team’s web-based report cards project sea level to the year 2050. The analysis now includes 51 years of water-level observations, from January 1969 through December 2019. The interactive charts by locality are available online at www.vims.edu/sealevelreportcards.