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Unseasonable wave of king tides hits

Ocean water levels in islands remain high

King tides this summer have not caused any significant impacts on Maui, though Kealia Pond has encroached on North Kihei Road. The Maui News / MATTHEW THAYER photo

King tides this summer have not caused any significant impacts on Maui, though Kealia Pond has encroached on North Kihei Road and docks at the Kihei Boat Ramp were nearly submerged recently.

Still, ocean water levels remain unseasonably high, said a University of Hawaii coastal expert.

“So far, to my knowledge there haven’t been any reports of significant impacts or damages on Maui, but the public is definitely noticing the high water levels,” said Tara Owens, a coastal hazards specialist with the University of Hawaii Sea Grant College Program and a liaison to Maui County.

King tides are caused by peak high tides coinciding with unusually high sea levels. The peak periods included dates in May, June and July, though the National Weather Service put out a special weather statement about the possibility of flooding due to king tides last weekend.

“Our current water levels are now equally high or even higher, than those past few months,” Owens said Thursday.

The Kahului tide gauge showed water levels 10 inches above predictions this week and 1 foot above predictions in Honolulu, she said.

This has led to the flooding at Kealia Pond, which was caused by the elevated sea levels as well as recent rain, she said. The Maui News received a Letter to the Editor from Laurie Barger, who said that the docks at the Kihei Boat Ramp were “almost submerged” Aug. 18.

The cause of the elevated sea levels are not just king tides but a “stacking effect” of several factors, Owens said.

A key factor is a “bulge of warm water circulating around the Hawaiian Islands” as seen on recent satellite imagery, she said. It is thought that the cause is partly related to a mesoscale eddy that shows up periodically and temporarily raises the sea surface by several inches.

Mesoscale eddies are spinning masses of water 50 to 300 miles in diameter, according to the website phys.org.

“These show up periodically and have the effect of temporarily raising the sea surface by several inches,” Owens said.

The Pacific Decadal Oscillation, sometimes described as a long-lived El Nino, and an El Nino are other factors causing continuing sea level anomalies and Pacific-wide sea surface variability, Owens said. Other factors include seasonal “astronomic high tides,” wave action related to seasonal swells and global sea rise due to climate change, she said.

“This has been an unusual summer with these other factors in various combinations leading to unusual flooding, wave run-up and/or erosion in localized areas,” she said.

The astronomic high tides will continue to diminish over the next couple of months and then increase in the winter king tides season, Owens said.

She encouraged the public to help document the high water levels by submitting photos, such as the observation at the Kihei Boat Ramp, to the Hawaii King Tides project at ccsr.seagrant.soest.hawaii.edu/king-tides.

* Lee Imada can be reached at leeimada@mauinews.com.