Moon wobble to deliver decade of coastal floods

Coastal regions across the US have been warned to brace themselves for increased coastal flooding in the middle of the next decade due to changes in the Moon’s gravitation pull.

Scientists at NASA and the University of Hawaii have undertaken the study which warned by the middle of the next decade towns across the US coats will face rapidly increasing high-tide floods, when a lunar cycle will amplify rising sea levels caused by climate change.

High-tide floods – also called nuisance floods or sunny day floods – are already a problem for many cities on the US Atlantic and Gulf coasts and thee are set to be exacerbated by the impact of climate change.

However scientists say the alignment of rising sea levels with a lunar cycle will cause coastal cities all around the US to undergo a decade of dramatic increases in flood numbers.

Led by the members of the NASA Sea Level Change Science Team from the University of Hawaii, the new study found that high tides will exceed known flooding thresholds around the country more often.

The floods will sometimes occur in clusters lasting a month or longer, depending on the positions of the Moon, Earth, and the Sun. When the Moon and Earth line up in specific ways with each other and the Sun, the resulting gravitational pull and the ocean’s corresponding response may leave city dwellers coping with floods every day or two.

“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. NASA’s Sea Level Change Team is providing crucial information so that we can plan, protect, and prevent damage to the environment and people’s livelihoods affected by flooding.”

“It’s the accumulated effect over time that will have an impact,” said Phil Thompson, an assistant professor at the University of Hawaii and the lead author of the new study, published this month in Nature Climate Change. Thompson pointed out that because high-tide floods involve a small amount of water compared to hurricane storm surges, there’s a tendency to view them as a less significant problem overall. “But if it floods 10 or 15 times a month, a business can’t keep operating with its parking lot under water. People lose their jobs because they can’t get to work. Seeping cesspools become a public health issue.”

The main reason for the concern is a regular wobble in the Moon’s orbit that takes 18.6 years to complete. NASA said there’s nothing new or dangerous about the wobble; it was first reported in 1728. What’s new is how one of the wobble’s effects on the Moon’s gravitational pull – the main cause of Earth’s tides – will combine with rising sea levels resulting from the planet’s warming.

“From a planning perspective, it’s important to know when we’ll see an increase,” said Ben Hamlington of NASA’s Jet Propulsion Laboratory in Southern California is a co-author of the paper and also the leader of NASA’s Sea Level Change Team. “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.”

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