Storm surges coinciding with a high tide can be particularly concerning, add to that a full moon and you have a guarantee of some coastal flooding. The role that rising sea level has in this equation may be more than linear. Some scientists are predicting that rising sea level will also mean higher tidal amplitude in the Gulf of Maine, already home of the world’s highest tides.

The extreme tides, up to 58 feet in the Bay of Fundy, are due to the shape and size of the basin, bounded at its mouth by Georges Banks and the Continental shelf. The resulting tidal resonance happens to be in sync with that of the open ocean.

Dr. David Greenberg of Fisheries and Oceans Canada at the Bedford Institute of Oceanography in Nova Scotia was the principle author of report published in 2012 in the journal Atmosphere-Ocean. The report, titled “Climate Change, Mean Sea Level and High Tides in the Bay of Fundy”, concludes that even in the absence of climate change, the Bay of Fundy and Gulf of Maine can expect to see an increase in high tides. Combined with the impacts of climate change, that tidal increase is expected to be approximately 1.64 feet over the next 50 years, and on the order of 3.28 feet by the end of the century.

Speaking from his Dartmouth N.S. office, Greenberg says, “if a storm surge happens at low tide, nobody cares, at least in the Bay of Fundy.” With variations in tidal range peaking in 18.6 year cycles (referred to as lunar nodal), it would be “bad luck” if surge and highest high tides coincided. The Goundhog Day storm of 1976, which destroyed waterfront businesses in Eastport, was just such an occurrence.

Since the last ice age, over 12,000 years ago, sea level has been higher (by 230 ft.) and lower (by 180 ft.) than present mean sea level. Greenberg explains that after the sea covered Georges Banks between 10,000 and 4,000 years ago the Bay of Fundy began experiencing 80 percent of present tidal range.

Recent geological discoveries in the upper reaches of the Bay of Fundy support an abrupt change in tides following an inundation into Minas Basin, resulting in the additional 20 percent of tidal range. “Oral records of this rapid change have been preserved for over 3400 years in the Legends of Glooscap,” explains Greenberg.

By studying data from tidal gauges from Boston to Halifax and throughout the Gulf of Maine, Greenberg has documented a continuing change in tidal range and through tidal models has made his predictions. The model shows “change of relative tidal range all the way through to Boston,” he said.

Art MacKay is an independent Canadian biologist who has lived and worked on Passamaquoddy Bay for over 50 years. He reviewed the recent Greenberg report and was impressed with what he found. “It is based on a solid foundation of research that traces post glacial warming and uplift. It is not just a reaction to the ideas of recent climate change.”

From his earliest jobs monitoring and making recommendations for the Point Lepreau nuclear power plant in southwestern New Brunswick and working on the ground floor of salmon aquaculture, MacKay has studied the region’s coastal ecosystem. “Huge changes are taking place” says MacKay, referring to ever increasing observations of southern species such as the sea squirt, which are found in great numbers on the local sea floor.

MacKay speculates that an increased tidal amplitude will impact the fisheries.

“A higher tide range will mean greater water velocity, that could mean a higher biodiversity which would be a boon to the filter feeding invertebrates.” However, he also warns that the Lepreau nuclear power plant, recently refurbished and
restarted, would be vulnerable to Sandy-like storms that may threaten the coast. “It’s a Fukushima waiting to happen.”

Leslie Bowman is a freelance writer living in Trescott, Maine.