Hawai`i tides running 8+inches higher than predicted--and this will go on for months.

Very strange stuff is going on at Hawai`i’s coastlines—sea levels have jumped in the past few months as much as they have in the past century.

Oceanographers are trying to figure out just what’s going on.

(Image: The pink to reddish areas in this graphic represent higher than normal sea levels. The blues are lower water. Credit: University of Hawai`i Sea Level Center.)

But what it means for now is that we are seeing eight to 10 inches higher high tides than we did a year ago.

If you’ve been at the docks, or at low-lying coastlines, you’ve seen it. This week will see some of the highest high tides.

University of Hawai`i coastal geologist Chip Fletcher said the superhigh water has been around for some time, and people seeing the unusual water levels and noting that it's strange are not mistaken.

“No it’s not a mistake - there has been a slug of high sea level for a year or more that has lingered around the islands,” Fletcher said.

Here is a graph that shows (red line) the actual sea levels, compared (blue line) to the normal predictions of sea levels. The waviness reflects tides. 

“Definitely an unusual event. We haven’t seen something like this during the past 20 years or so,” said Mark Merrifield, coastal geologist with the University of Hawai`i School of Ocean and Earth Science and Technology.

The good news is that this sudden increase may be temporary. Merrifield said some forecasts suggests the superhigh tides will last at least through the summer.

“Elevated sea levels around Hawaii are likely to continue through the forecast period, potentially enhancing extreme high tides during May, June, and July,” says this website from the University’s Sea Level Center. 

That doesn’t mean the high tides end in July—just that July is as far in the future as the forecast goes.

This is not a global phenomenon. The Pacific Ocean appears to be bumpy. The sea levels are higher in some areas (as around the Hawaiian Islands) and lower in other areas (In coming months, “sea levels are likely to be near or below-normal in the tropical northwestern Pacific {Yap, Guam, Chuuk, and Pohnpei} and above-normal in the equatorial central Pacific {Kiritimati}.”)

Merrifield said researchers are working to try to understand what’s going on.

Meanwhile, the background global sea levels continue to rise, and at an increasing pace.

This article from the American Geophysical Union says sea levels are now rising 25 percent faster than they were a quarter-century ago.

The article cites this study published in Geophysical Research Letters. 

The increase appears, the report said, to be “mostly due to Greenland mass loss increase and also to slight increase of all other components of the budget.”

The superhigh water of the past few months, on top of the increasing rate of sea level rise, puts the Islands at significantly increased risk from events that drive water ashore, like tsunami and major storms.

© Jan TenBruggencate 2017