The rise and fall of the tides is a predictable phenomenon caused by the gravitational pull of the sun and the moon relative to the earth. King tides are also a regular occurrence signifying the highest tides of the year. They typically occur during summer months when the moon is either new or full and is closest to the earth.
This year, sea levels were anomalously high in the pacific basin, resulting in coastal flooding during these king tide events. April’s king tide broke the record set over 100 years ago, with a tide that rose 9 inches above the predicted level.
So what is causing this sea level anomaly? According to scientists at the University of Hawaii, a combination of ocean eddies with high centers, sea level variability from a recent El Nino, and long-term sea level rise caused by global warming all contribute to the excessive tides. Additionally, summer swells can bring even more water in towards the shore exacerbating the effect.
The result is often seen as coastal flooding. According to NOAA, the sea level around Kauai is running as much as a foot greater than the levels predicted by the tide charts. NOAA and the National Weather Service often issue special weather statements predicting tidal flooding, like the one issued on Tuesday, August 22nd when peak water levels are expected in the late afternoon and early evening. This can be seen near boat harbors and in beach areas through Wednesday evening.
What does it mean for visitors to the island? Hawaii’s tidal range is actually much smaller than those seen in mainland coastal areas. Still, if you are not expecting it, water can come up fast and take your belongings with it when it retreats into the sea. It can also damage electronic devices that may contain your vacation photos. It would be wise to check the tide charts and pay attention to where you put your belongings on the beach, especially if you plan leave them unattended.
Sea Grant created the Hawaii and Pacific Islands King Tides Project, to collect more data about these tidal events. The project involves citizen science where folks like you and me can submit pictures through an app called Liquid Mobile Data Collection that helps document coastal flooding. Scientist can then compile and evaluate the king tides and high water data that is submitted. Documenting the king tides is important to scientists to verify their models of wave run-up and harbor flooding. These events also give us a glimpse into the future as to what to what kind of flooding and subsequent erosion we can expect to see as sea levels continue to rise.
If you are interested in participating in the study, you can download the app and check out the Pacific Islands Kind Tides Project web-page for more information.