A flip in a natural moon cycle combined with rising seas from climate change will cause rapid and “dramatic” increases in flooding along U.S. coastlines by the mid-2030s, according to a NASA study.
High-tide floods – also called nuisance floods or sunny day floods – are already a familiar problem in many cities on the U.S. Atlantic and Gulf coasts. In 2019, the National Oceanic and Atmospheric Administration (NOAA) reported over 900 such high-tide floods.
The moon’s natural orbit is responsible
According to CTV News Canada, the moon’s orbit is not a natural circle, but a wobbly, elliptical path that takes 18.6 years to complete. The wobble is not new or dangerous, according to NASA, and was first reported in 1728.
The moon’s tilt changes over its cycle, and that motion affects the ebb and flow of Earth’s tides. For about half of this cycle, high tides are suppressed, keeping rising sea levels in check, but for the remainder of the cycle, the moon’s wobble boosts the effects of sea-level rise.
“It doesn’t change the strength of tidal forces or the gravitational forces of the moon, but it tends to increase the range between the highest and lowest tides of the day,” said Philip Thompson, an assistant professor in the department of oceanography at the University of Hawaii at Manoa and lead author of the study. “In other words, it tends to make the highest tides even higher and the lowest tides even lower.”
However, in research published in the journal Nature Climate Change on June 21, 2021, NASA researchers found that climate change’s impact on rising sea levels will only be amplified by the moon’s gravitational pull causing persistent and dramatic high tides.
What this means for the future is that the “nuisance floods” coastal communities are already dealing with could become widespread for almost all coastal communities in this country and the rest of the world by the middle of the next decade, reports NBC News.
“This is the point in time when things will begin to rapidly change,” Thompson said. “When we think about when we need to improve and have things ready with our drainage systems and infrastructure, this gives a target point.”
The researchers found that from the mid-2030s into the following decade, the changing lunar cycle will cause clusters of flooding in coastal communities. In St. Petersburg, Florida, for example, high-tide flooding is projected to increase from six or seven events a year to 10 times that amount in just over a decade.
“But if it floods 10 or 15 times a month, a business can’t keep operating with its parking lot underwater. People lose their jobs because they can’t get to work. Seeping cesspools become a public health issue,” Thompson said.
