A new study published by NASA scientists forecasts that the United States will encounter frequent, severe coastal floods due to an expected wobble by the Moon in the 2030s, giving Americans only 9 years to prepare for impact. The new study shows that high tides will exceed known flooding thresholds around the country more often; it also shows 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.
The cause for the increased flood threat is a cyclical orbit of the Moon. First reported in 1728, it appears the Moon wobbles during its 18.7 years to complete an orbit. In the 2030’s, the Moon’s wobble in its orbit is forecast to be close enough to drive significant flooding along the coastlines, even if there’s no coastal storm present.
“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.
“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. 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.”
With the moon wobble expected in the 2030’s, high tides are forecast to become higher while low tides will become lower. The study projects that most of all U.S. mainland coastlines, Hawaii, and Guam will be impacted, with only far northern coastlines, including Alaska’s, being spared due to long-term geological processes.
“From a planning perspective, it’s important to know when we’ll see an increase,” Ben Hamlington said. Hamlington, of NASA’s Jet Propulsion Laboratory in Southern California, is a co-author of the paper. “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.
The United States will occasionally experience very high tides when the Moon is close enough to have a significant influence on them. Known as “King Tides”, coastal communities could experience flooding from the ocean and surrounding bodies of water such as bays and inlets even under sunny skies with no storms around. With the Moon wobbling closer in the 2030s, these King Tides could become a very frequent occurrence.