Higher tides affecting East Coast, especially mid-Atlantic

Scientists are closely watching unusually high tides along the entire East Coast, especially in mid-Atlantic states including Virginia, where average daily levels are running between 6 inches and 2 feet above predicted norms.

One veteran researcher at the Virginia Institute of Marine Science, John Boon, said he suspects the trend could be the beginning of a decade-long phenomenon of high water caused by an El Niño-like effect in the Atlantic.

“It’s possible we’re entering a new cycle,” he said this week.

Boon, a professor emeritus of marine science who has studied tides most of his career, described how Atlantic wind patterns and currents can subtly shift, often without explanation. The shift, in turn, pushes more water onto East Coast beaches, marshes and coastline through higher tides.

The National Oceanic and Atmospheric Administration has received many calls in recent weeks from concerned residents, waterfront homeowners and  scientists along the East Coast, said Michael Szabados, an official with the agency.

Likewise, the Virginia Institute of Marine Science, based in Gloucester Point, has fielded phone calls and e-mails from anxious residents and others who rely on the ebb and flow of daily tides, officials said.

Boon said the practical effects of the trend can be both good and bad – good for people who normally have trouble getting their boats out beyond local sandbars and mud flats; bad if the region were to be hit with a tropical storm or hurricane. Storm surge already is a major threat in hurricanes, especially in low-lying Hampton Roads. But if water is running unusually high from an ocean anomaly, Boon said, “you face a double-threat of significant flooding.”

The extreme tides, he and other scientists said, have occurred before and can last, on and off, for years at a time before suddenly changing back to normal.

“There’s no scientific debate that these anomalous cycles happen,” Boon said. “It’s what causes them that’s debated.”

NOAA noticed the trend taking off in early June, affecting states from Maine to Florida. In Baltimore in mid-June, for example, the agency documented tides 2 feet above predicted levels.

The events are continuing, though they have slightly subsided in recent days, said Szabados, who is director of NOAA’s Center for Operational Oceanographic Products and Services, based in Silver Spring, Md.

“It’s more intense than usual and is happening at a time of year when we don’t usually see such variability,” Szabados said Thursday. “We’re definitely interested and definitely investigating it.”

NOAA posted an  alert  about the trend on July 2 on its Web site, www.tidesandcurrents.noaa.gov, and continues to update it, Szabados said.

El Niño occurs every seven or eight years on average, affecting weather patterns along the Pacific Ocean.

Similarly on the Atlantic, quirky shifts in atmospheric pressure and winds, known as the North Atlantic Oscillation, contribute to weather variability – and might be at play now, said Larry Atkinson, an oceanographer at Old Dominion University in Norfolk.

Atkinson said that what Hampton Roads is experiencing now will likely become the norm in 30 or 40 years due to sea level rise associated with the slow warming of ocean temperatures.

“This is a little taste of the future,” he said. “It basically exposes our vulnerabilities to high water.”

Atkinson said people who live or work away from local creeks and rivers might not notice the change. But “ship captains can tell, and the insurance companies know what is going on,” he said.

Scientists do not think the unusually high tides are due to sea level rise because, as Szabados explained, “these have happened suddenly, not slowly over time.”

Scott Harper, (757) 446-2340, scott.harper@pilotonline.com