An unexplained coastal phenomenon last Tuesday afternoon caused quite a stir from Bristol to Cundy’s Harbor when at low tide a huge wave formed near coastal shores and caused some damage to ramps and floats.
Rapid atmospheric changes at the time are the most likely explanation a Gulf of Maine Ocean Observing System (GoMoos) study discovered after examining environmental circumstances surrounding the incident and ruling out the possibility of a quake on the ocean floor or shore in absence of any seismic activity.
Speculations early last week on the cause ranged from a rogue wave or a seiche, to a possible slip fault, but investigation into the freak occurrence resulted in the explanation, according to Philip Bogden, CEO of the Gulf of Maine Ocean Observing System (GoMoos).
“It was what we call in the business a ‘bomb,'” Bogden said. “The plausible explanation is it was an oscillation in the bay.”
Bogden said in an interview late last week, high winds of 20 knots heading in a northerly direction suddenly shifted to a southerly direction producing a rise in ocean waters because of an “oscillation” peaking between four and 12 feet in height.
He described it as much like a seiche, which is a phenomenon that usually occurs in a lake when high winds force water to an enclosed area and suddenly subsides causing ocean water to slosh back and forth (oscillate) pushing the water upward before going back to the normal level.
“It blew on the estuary all at once and then went away all at once,” Bogden said.
The suddenness factor produced the conditions that make up what he called an atmospheric bomb affecting the water in the way it did, in his estimation. Ordinarily such changes in winds and overall atmosphere would not have produced such a violent impact on the Midcoast waters but instead would have happened over a day or two affecting coastal waters only minimally. “You don’t get the magnification and oscillation,” he said.
That is how oceanographer Dr. David Townsend of the University of Maine at Orono described a seiche and last week said he thought it might have been, though not knowing the specific weather conditions at the time, which the National Weather Bureau later reported.
So much turbulence occurred in Boothbay Harbor in particular, causing damage to a couple of ramps and attached floats in Lobster Cove, setting one of the ramps with floats completely free from the dock, according to Boothbay Harbor EMA Director Dave Benner.
On Oct. 29, Benner said, “The National Weather Service has been working on it and trying to come up with some kind of explanation.”
GoMoos received information from the National Weather Service about the winds and atmospheric conditions that set up such a strange set of circumstances, including the tide going out.
Benner said in the Mill Cove area, the raging waters popped up planks from floats there and pushed pilings at an angle, which later returned to their original upright positions.
Benner personally went out to the areas to witness the unusual ocean happenings and estimated the height of the wave around 3:10 p.m. last Tuesday to be four feet high. “It depends on who you talk to,” he said.
