A Small 'Wobble' in the Moon's Orbit Could Fuel Rapid Flooding in the 2030s

And we'd better start planning now, before it's too late.
Brad Bergan
Honolulu flooded from high tides.Hawaii Sea Grant King Tides Project

It can always get worse.

And in recent years, we've seen climate change increase the number and strength of hurricanes, in addition to other seriously damaging weather events globally. But something else, more gradual yet still worrying is on the horizon, and it could change the shape of life on the coasts of the U.S.

Combined with rising sea levels due to global warming, the moon's lunar cycle will amplify low and high tides in the late 2030s, which could lead to serious coastal flooding throughout the U.S., according to a recent study published in the journal Nature Climate Change.

And we'd better start planning now, before it's too late.

Sea levels may rise 12 ft higher than 2000 levels by 2100

In coastal areas, high-tide floods (also termed "nuisance floods"), happen once the tides rise roughly 2 ft (0.6 m) higher than the daily average for high tides, which leads to flooding in streets, or through storm drains. These floods are less serious than major catastrophic events we typically associate with major climate events, but they still have a serious effect on society: forcing businesses to close, filling streets and ruining homes, and enabling cesspools to flood and spill into public areas. And the longer such a scenario lasts, the more lasting the damage to a community.

In 2019, more than 600 such floods happened in the U.S., but a new study from NASA suggests that nuisance floods will likely grow in frequency by the 2030s, and will involve most of the U.S. coastline inundated with four times the number of high-tide flood days each year for a full decade, or longer. Longer coastal flood seasons will cause serious disruptions to lives and livelihoods, especially if communities don't immediately start planning for the eventuality, warn the researchers of the study. "It's the accumulated effect over time that will have an impact," said Assistant Professor Phil Thompson of the University of Hawaii in a NASA blog post. "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," said Thompson. "Seeping cesspools become a public health issue." And there are multiple causes behind this development, the first of which is, predictably, the sea level rise from global climate change. Glacial ice continues to melt at a record rate, dumping colossal volumes of meltwater into the ocean. This has increased average sea levels by roughly 8 to 9 inches (21 to 24 cm) since the year 1880, and roughly a third of that increase happened in the last 25 years. If trends continue, sea levels could rise 1 to 12 ft (0.3 to 2.5 m) higher than where they were in 2000, by 2100. Of course, this in part could change depending on whether humans sufficiently reduce greenhouse gas emissions in the near future.

The moon will amplify high and low tides in the 2030s

However, the moon, too, could play a vital role in the exacerbation of flooding in the 2030s, when its orbit's "wobble", which is due to a change in its relative position to Earth every 18.6 years, could amplify the cycle of high and low tides, making lower tides lower and higher tides higher. As of writing, we're already in a tide-amplifying cycle of the moon, and the next one will happen in the mid-2030s — when worldwide sea levels will already have increased enough for these amplified tides to create a perfect storm of tide-raising forces, where the combined effect of the lunar cycle and climate change-linked sea-level rise would exacerbate high-tide flooding throughout the entire coastline of the United States. In just 14 years, high-tide flooding will shift "from a regional issue to a national issue with a majority of U.S. coastlines being affected," said the study authors.

This is a scary development, but it's important to note that we still have time to minimize the damage from potentially devastating flooding due to the combined effects of lunar cycles and sea-level rise. Perhaps not enough to avoid the rising waters altogether, but planning for it, financially, in terms of infrastructure, where you live, and social support systems (personal or top-down governance) is crucial. And with a little more than a decade to go, most of us can prepare adequately. If we decide to take it seriously.


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