Rising seas mean higher tides, flooding ‘new normal’
More higher-than-normal king tides are forecast to arrive with the new moon this week, a final round in a fall season that flooded coastal areas and reinforced the growing impacts of a rising sea.
The East Coast is on pace to see record-breaking tides this year, and tides along the Gulf Coast also are trending higher, said William Sweet, a National Oceanic and Atmospheric Administration oceanographer.
“It’s not normal, but unfortunately it’s becoming the new normal,” said Sweet, lead author of NOAA’s annual report on high tide flooding.
That’s because rising sea levels are pushing the year’s highest tides even higher, Sweet said. Tides typically rise higher and fall lower during new moons and full moons, and the highest tides of the year, often in the fall, are referred to as king tides.
‘The future is here’
But as temperatures warm around the world, sea levels are rising as a result of the expansion of warming ocean water and the melting of land-based glaciers — turning king tides into record-breaking tides and fulfilling scientists’ predictions on the effects of warming global temperatures.
“As sea level rises, these (tide) records will continue to fall, as communities flood more often from typical changes in currents and winds and tide,” Sweet said. “Whether it’s the king tide in Miami or the subtropical storm off the northeast coast, this is to be expected; what we predicted is occurring. The future is here.”
All along the coast, tidal gauges — including some that have been tracked for more than a century — tell the story. Sweet calls them “unbiased sentinels of the sea.”
“They’re telling an important story, that sea level is on the rise and flooding is happening more often,” he said. “There are stories in many communities, whether it’s Boston or New York, Ocean City, Atlantic City, Baltimore, Annapolis or Charleston.”
The next new moon — when the moon passes between the earth and the sun — occurs Tuesday.
NOAA’s fall king tide outlook called for higher tides this week, but the tides aren’t forecast to be as high as they were in September and October when flooding occurred in many locations.
A combination of moon-driven high tides, tropical storms and rising sea levels were blamed for “exceptionally high” tides in South Florida this fall, particularly in the Keys, said Jason Evans, an associate professor at Stetson University in DeLand, Florida.
Parts of one flood-prone area in the Keys have been flooded for more than 80 days. In Jacksonville, Florida, the National Weather Service office has issued more coastal flood advisories this year than in any of the past 12 years.
November will be the fifth month in a row when record-high monthly average water levels are set at Virginia Key near Miami, said Brian McNoldy, senior research associate at the University of Miami.
A slowing of the Gulf Stream current, also related to climate warming, may be a key factor combining with sea level rise to push water levels higher, he said. So far this year, water levels in Miami have been above the mean high tide mark nearly a third of the year.
Tide levels were higher than NOAA predicted for much of September and October at locations along the coasts that include Port Aransas, Texas; Providence, Rhode Island; Woods Hole, Massachusetts, and Mayport, Florida.
During the new moon high tides in New Jersey in early September, Lisa Auermuller received a phone alert from her children’s school that buses would be dropping kids off on higher ground because they couldn’t get down some roads near Auermuller’s home in Little Egg Harbor.
It was the second such alert in about five years and the flooding lasted for about four days, said Auermuller, assistant manager of the Jacques Cousteau National Estuarine Research Reserve for Rutgers University. She helped organize a statewide crowd-sourced effort “to get citizen scientists to take pictures of what they were seeing” during the king tides and document vulnerable areas.
“We saw the impacts and effects quite a far way up” the Mullica River, Auermuller said. “The flooding was that extreme all over the coastal areas of New Jersey.”
The Rutgers campaign is part of a movement by agencies, researchers and nonprofits around the nation to document the flooding. Events, including king tide days and photo contests, also were held in New Hampshire, Washington and California.
Continuing into November, full moon high tides were pushed higher along the coast from North Carolina to Florida thanks in part to an offshore storm. In Beaufort, North Carolina, the weather service reported Front Street flooded as the high tide reached the threshold for moderate flooding.
NOAA’s Sweet would like to see the term “king tide” updated for what he sees as a new reality. After all, king tides have always been around, but communities weren’t flooding because of them 20 years ago.
“We might as well call it what it is,” he said. “It’s sea level rise flooding.”
And the increasing number of flooding events is exposing just how vulnerable many low-lying coastal locations are to the rising sea, Sweet added.
“It’s not going away,” he said. “It’s expected to continue to grow – in depth and frequency – and spread. That’s our future.”