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The moon wobble

A barely perceivable phenomenon could have an outsized effect on coastal populations


iStock.com/johnemac72

The moon wobble

Humans have long charted the phases of the moon, observed and predicted eclipses, and defined its elliptical orbit. Now NASA scientists have released a report studying the effects of one of the moon’s lesser-known characteristics: its wobble.

The subtle changes in distance, tilt, and orbit of the moon may not look like much to the naked eye. But NASA scientists who studied the phenomenon say the lunar wobble could significantly alter tidal patterns on Earth. According to the researchers, who published their work in Nature Climate Change in June, it will likely lead to increased risk of flooding during the 2030s.

“This is eye-opening for a lot of people,” NASA scientist and study co-author Ben Hamlington told Reuters. “It’s really critical information for planners. And I think there’s a great amount of interest in trying to get this information from science and scientists into the hands of planners.”

Because the moon makes one full revolution on its axis per orbit around the Earth, we only see one of its faces. But sometimes that face shifts as the moon’s tilt or the shape of its orbit changes. Scientists call the subtle changes libration. When time-lapse photography speeds up the process, the human eye perceives these changes as a wobble.

According to NASA scientists, the moon’s wobble falls into predictable 18.6-year cycles that alter its gravitational effect on tides. During the first half of that nearly two-decade cycle, the distinction between high tide and low tide weakens—high tides shrink and low tides grow. During the second half of the cycle, the pattern reverses, with higher high tides and lower low tides.

Scientists pulled data from 89 tide gauges that cover almost every U.S. coastline. According to the researchers, the moon will wobble into the second half of its libration cycle in the 2030s, heightening the risk of tidal flooding in low-lying areas.

Scientists first noticed the moon’s libration cycle in 1728, according to NASA. The researchers expressed concern that rising sea levels from climate change will exacerbate the upcoming cycle’s increased tidal intensity, amplifying flooding and forcing governments of coastal populations into difficult decisions.

Though flooding likely won’t compare to the storm surge from a hurricane, high-tide floods could become routine. “It’s the accumulated effect over time that will have an impact,” University of Hawaii oceanographer and study co-author Phil Thompson said. “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.”


John Dawson

John is a correspondent for WORLD. He is a graduate of the World Journalism Institute, the University of Texas at Austin, and previously wrote for The Birmingham News. John resides in Dallas, Texas.

@talkdawson

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JimVC

The moon rotates on its axis at roughly the same rate as it revolves around the earth, not the rate of earth's rotation.
OK, once again, I am logged in, but I can't post a comment without clicking My Account, then Back, then Sign In, then Back again, then retype the comment!!!!!
At least, they finally got the time zone right, but comments are still in backwards order!

Are you ever going to fix this???????

WORLD's Mickey McLeanJimVC

Thank you for pointing out the error in our report. We have edited it.
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Mickey McLean
Executive Editor for Audience Engagement

CWIL4278

If it's an 18.6 year cycle, then what is going to happen in the 2030s would have also happened in the 2010s. Do you remember all the coastal flooding from high tides in the 2010s? Nope. Didn't happen. More hysteria by the New York Times.

mrbobmac

This is very interesting news! It is good to know now, lest 10+ years from now *all* of the blame for rising tides is based on 'climate change'. I cannot speak into the science behind climate change (i.e., the assertion that increased temperatures, melting polar caps, more powerful storms, bigger droughts, etc.) being caused by the use of fossil fuels. But it is helpful to remind us that fires burned forests long before vacation homes were there. The Old Testament is filled with droughts and rainstorms, the Nile floods and slackens. It's *normal*. I hope that's remembered a decade from now!

"What has been is what will be, and what has been done is what will be done, and there is nothing new under the sun." ~Ecclesiastes 1:9