‘King tide” is not technically a scientific term, but it should be. It describes a specific tidal happening that people care a lot about — especially now.
And shortly after 2018 begins, we’ll experience an exceptionally rare and noticeable king tide. It‘ll peak at 3:54 a.m. Jan. 1 in Honolulu when our New Year’s Eve champagne buzz has worn off.
Regular tides are caused by the moon’s gravitational pull and to a lesser extent by the sun. King tides are caused when two celestial events take place simultaneously: a spring tide and perigee.
Spring tides — the highest tides of the month — occur when the moon, sun and Earth line up, causing the gravitational pull of the moon and sun to complement each other. These tides generally occur twice a month year-round, meaning the scientific term “spring tide” is a bad one.
Perigee, you might remember from eighth-grade science class, is when the moon is nearest to Earth and exerts the greatest gravitational pull on our oceans. Perigee adds about two inches to high tides.
The New Year’s king tide will not only involve a spring tide and perigee “supermoon.” We’ll also experience perihelion on Jan. 2 when the Earth’s elliptical orbit is nearest the sun. This improbable celestial mix may make the first king tide of 2018 even more remarkable.
All this would just be cool science and coincidence but for one glaring thing: climate change. King tides coupled with sea-level rise due to human-caused climate change spell trouble for coastal peoples.
Predictions on the amount of sea level rise we’ll encounter by 2100 vary, but a number of scientific conclusions are unequivocal:
>> Sea levels are rising and will continue doing so into 2100.
>> The rate of rise may not be linear (the same from year to year), meaning it may increase.
>> Our behaviors can affect the amount of sea-level rise over the next decades and centuries.
King tides are as old as the Earth and moon but have become threatening and damaging due to climate change. So now the term has inundated our ocean-awareness vocabulary and is used the world over.
King tides are well known to my Chaminade University students from the low-lying Pacific islands of Majuro, Kiribati, Palau and Chuuk. Their homemade videos show how recent king tides — combined with sea-level rise — covered coastal crops, infiltrated fresh-water tables, flooded homes and even immersed burial sites of ancestors.
The impact of sea-level rise coupled with king tides in the Pacific is captured in a powerful slam poem, “Dear Matafele Peinem,” written and performed by Marshallese native Kathy Jetnil-Kijiner at the opening ceremony of the United Nations’ Climate Summit 2014.
Hawaii awakened to the term “king tide” on April 26 and 27, May 25 and June 23 of this year when photographs and eyewitnesses documented higher-than-usual tides.
The weekly fireworks show at Hilton Hawaiian Village had to be cancelled more than once. The ocean reached the wall at Ala Moana Beach Park. Sand covered the walkway along Waikiki’s Kuhio Beach. These and many other noticeable extremes took us to the consciousness-raising tipping point.
We cannot control what happens when something celestially rare and wondrous occurs this New Year due to a king tide caused by a supermoon, spring tide and perihelion.
We can, however, control climate change and its effects. Doing so means we could one day return to a time when king tides are much less noticeable and not damaging.
So when making New Year’s resolutions and gazing at the stunning supermoon, let’s all resolve to be Pacific climate warriors determined to stop the causes of climate change in Hawaii and globally.
Let’s adopt better practices that leave us simply appreciating, not fearing, amazing celestial events such as the one awaiting us at the dawn of 2018.
Associate Professor Gail Grabowsky directs the Environmental Studies program at Chaminade University of Honolulu.
