For the second time in a month, Hawaii’s coastlines have been swamped by epic tides. The phenomenon, known as a king tide, is actually a convergence of a few different factors: high lunar tides, rising sea levels associated with last year’s strong El Niño and climate change, swirling pockets of ocean eddies, and a robust south swell—that is, big waves rolling onto south-facing shores.
King tides happen routinely in the Hawaiian Islands—a few times a year, usually—but this year’s batch have been particularly extreme. Data from federal tide stations around Hawaii show that water levels have been up to six inches above predicted tidal heights since early last year. In April, levels peaked at more than nine inches above predicted tides and broke the record high for any water level around Hawaii since 1905. Scientists say the record is likely to be broken again in 2017.
Several Honolulu roadways have been submerged. Beaches have been washed out. Beachfront hotels have canceled shorefront entertainment and readied generators. Property owners living near the coasts were told to move electronics and other valuables up to the second floor of their houses and park their cars elsewhere. People photographed fish swimming down the streets. And all around the islands, small mountains of sand have been deposited in parking lots and other strange places—spots the waves should never reach.
For the people of Hawaii, alarm bells are ringing. King tides like this aren’t just a historic anomaly; they’re a sign of what’s to come. “Within a few decades this will be the new normal,” said Chip Fletcher, associate dean of the School of Ocean and Earth Science and Technology at the University of Hawaiʻi, in a university statement. “Hawaii should consider this a practice run, and reevaluate policies and development practices accordingly.”
“It’s a risk big enough to get the attention of officials who usually watch things like hurricanes and tsunamis,” said the local TV reporter Gina Mangieri, who reported for KHON that emergency-management officials had called for “all-hands-on-deck coordination” across state, county, and federal agencies to protect critical infrastructure and the public.
Scientists believe Hawaii could experience a sea-level increase of three feet by the year 2100, which is in line with global predictions of sea-level change and which would substantially reshape life on the Islands. That’s part of why scientists are enlisting volunteers to help photograph and describe incremental high tides across Hawaii.
“First-person experiences that are place-based and familiar reinforce that climate changes impacts are local in nature and not a distant phenomenon,” the university’s King Tides Project website says. More than 60 volunteers have submitted more than 900 photos so far.
Scientists have measured other significant environmental changes already under way. The rate of warming air temperature in Hawaii has quadrupled in the past four decades. The cooling trade winds that help bring rain have diminished. Overall rainfall is declining, raising the risk of drought and threatening freshwater supplies, according to a 2014 report by the University of Hawaii Sea Grant College Program.
“It is now widely accepted that human activities are affecting global climate systems in a significant way,” the authors of that report wrote. “While there are disagreements about the exact nature, magnitude, and timing of these changes, the science is clear that global climate change is being observed.”
Hawaii officials are already in the process of developing statewide maps to predict and track Hawaii’s most vulnerable areas for erosion and flooding, outlining how climate change will alter the Islands in 2030, 2050, 2075, and 2100.
In the meantime, an even bigger king tide than the ones in April and May is forecast for June.