A ‘wobbling’ Moon will cause devastating worldwide flooding in the 1930’s, the NASA has warned, prompting scientists to mark coastal cities as under threat from “rapidly increasing high tide floods” which could occur in clusters lasting a month or more.
The agency explained that the moon’s “wobble” affects its gravitational pull – which is the main cause of Earth’s tides. The wobble, which was first reported in 1782, takes about 18.6 years to complete, during half of which, Earth’s regular daily tides are suppressed.
For the Moon to complete one wobble, it takes 405,400 km (251,900 mi) (avg.). The Moon orbits Earth in the prograde direction and completes one revolution relative to the Vernal Equinox and the stars in about 27.32 days (a tropical month and sidereal month) and one revolution relative to the Sun in about 29.53 days (a synodic month).
Led by the members of the NASA Sea Level Change Science Team from the University of Hawaii, the new study shows that high tides will exceed known flooding thresholds around the country more often.
What’s more, the NASA report says, 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.”
Why will cities on such widely separated coastlines begin to experience these higher rates of flooding at almost the same time? The main reason is a regular wobble in the Moon’s orbit that takes 18.6 years to complete. 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.
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. He notes that the findings of the new study are a vital resource for coastal urban planners, who may be focused on preparing for extreme events rather than more high-tide floods.
“From a planning perspective, it’s important to know when we’ll see an increase,” Hamlington said.
“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.”
A high-tide flood tool developed by Thompson already exists on the NASA team’s sea level portal, a resource for decision-makers and the general public. The flood tool will be updated in the near future with the findings from this study.
