‘Wobble’ in moon’s orbit to cause flood surge on every US coast in 2030s, NASA predicts

(NEXSTAR) — Beware, coastal communities. The U.S. is set to face a surge in high-tide floods along its coasts due to a “wobble” in the moon’s orbit coupled with global warming, according to NASA.

Starting in the mid-2030s, a lunar cycle will amplify rising sea levels fueled by climate change, causing rapidly increasing high-tide floods on every U.S. coast, according to findings of a new study by the NASA Sea Level Change Science Team from the University of Hawaii.

“Low-lying areas near sea level are increasingly at risk and suffering due to the increased flooding, and it will only get worse,” said NASA Administrator Bill Nelson. “The combination of the moon’s gravitational pull, rising sea levels, and climate change will continue to exacerbate coastal flooding on our coastlines and across the world.”

The lunar cycle, which dictates the suppression or amplification of the Earth’s regular daily tides, is behind the expected tidal surge.

The wobble in the moon’s orbit, which takes 18.6 years to complete, is not unusual and was first reported in 1728. But what’s new is how its effects on the moon’s gravitational pull — the main cause of the planet’s tides — will combine with rising sea levels resulting from Earth’s warming, NASA said.

“In half of the Moon’s 18.6-year cycle, Earth’s regular daily tides are suppressed: High tides are lower than normal, and low tides are higher than normal. In the other half of the cycle, tides are amplified: High tides get higher, and low tides get lower,” NASA said. “Global sea level rise pushes high tides in only one direction – higher. So half of the 18.6-year lunar cycle counteracts the effect of sea level rise on high tides, and the other half increases the effect.”

The cycle is currently in the half that amplifies tides, but sea levels along most U.S. coastlines have not risen so much that high tides regularly top flooding thresholds.

That won’t be the case by the mid-2030s, when the rise of global sea levels is expected to cause a jump in flood numbers.

“Global sea level rise will have been at work for another decade,” NASA said, adding that only far northern coastlines, such as Alaska’s, will gain a respite of at least another decade as a result of long-term geological processes that are causing these land areas to rise.

The study, published in the journal Nature Climate Change, is the first to consider all known oceanic and astronomical flood causes, NASA said. Researchers, who studied 89 tide gauge locations in every coastal U.S. state and territory but Alaska, created a new statistical framework.

“From a planning perspective, it’s important to know when we’ll see an increase,” said Ben Hamlington, the leader of NASA’s Sea Level Change Team and a co-author of the paper. “Understanding that all your events are clustered in a particular month, or you might have more severe flooding in the second half of a year than the first – that’s useful information.”