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Study Shows Moon 'Wobble' Contributing to More US Coastal Flooding

FILE - A pink supermoon rises in the night sky over Coit Tower in San Francisco, California, April 26, 2021.
FILE - A pink supermoon rises in the night sky over Coit Tower in San Francisco, California, April 26, 2021.

A NASA-University of Hawaii study warns that upcoming changes in the moon's orbit coupled with higher ocean levels could lead to record coastal flooding on U.S. coasts in the next decade.

The study, conducted by the NASA Sea Level Change Team at the University of Hawaii, and published last month in the scientific journal Nature Climate Change, says a regularly occurring change in the moon’s orbit around the earth will raise ocean water levels along U.S. shorelines.

The NASA researchers say the so-called “wobble” in the moon’s orbit is part of an 18.6-year cycle, recorded as far back as 1728. During half of the cycle, the moon creates lower high tides and higher low tides; the other half creates higher high tides and even lower low tides.

The phenomenon is expected to peak the mid-2030s and is occurring just as coastal flooding is on the rise due to higher ocean levels linked to the effects of climate change. A report released Wednesday by the U.S. National Oceanic at Atmospheric Administration (NOAA) says the U.S. saw record levels of coastal flooding in the past year.

NOAA say flooding at high tide, often called “nuisance” or “sunny day” flooding, has regularly occurred within many coastal communities as water routinely sloshes into streets, yards and businesses.

But the agency reports from May 2020 through April 2021, U.S. coastal communities saw twice as many high tide flooding days than they did 20 years ago. They expect the near-record high tides trend to continue through April 2022, as well as in decades to come.

NOAA oceanographer and author on the NASA study William Sweet told The Washington Post the combination of the moon’s orbit wobble and rising sea levels is “sort of a double-whammy” that means coastal communities are likely to expect even greater flooding than they might otherwise in coming years, unless they adapt and fortify their shorelines.

NASA’s Sea Level Change team leader Ben Hamlington said communities and urban planners need to plan for more extreme flooding in the future.

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