HTF, also called nuisance floods or sunny day floods, are already a familiar problem in many cities on the US Atlantic and Gulf coasts. (Representative image: Reuters)
High-tide floods will increase rapidly across the world, especially the United States, in the mid-2030s and it is linked with Earth's neighbour, the Moon, said National Aeronautics and Space Administration (NASA).
According to a study by the American space agency, a 'wobble' in the Moon's orbit combined with sea-level rise (SLR) due to climate change will lead to devastating high-tide floods (HTF).
HTF, also called nuisance floods or sunny day floods, are already a familiar problem in many cities on the US Atlantic and Gulf coasts. However, in the mid-2030s, the alignment of rising sea levels with a lunar cycle will cause coastal cities all around the US to begin a decade of dramatic increases in flood numbers, said the study that takes into account all known oceanic and astronomical causes for floods.
“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,” said NASA Administrator Bill Nelson.
Low-lying areas near sea level are increasingly at risk and suffering due to the increased flooding, and it will only get worse, he added.
The study further predicts that during the period, these floods will sometimes occur in clusters for 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,” said the study led by the members of the NASA Sea Level Change Science Team from the University of Hawaii.
Explaining the result, the study said: “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.”
“Half of the 18.6-year lunar cycle counteracts the effect of sea-level rise on high tides, and the other half increases the effect. The Moon is in the tide-amplifying part of its cycle now. However, along most US coastlines, sea levels have not risen so much that even with this lunar assist, high tides regularly top flooding thresholds.”
The situation will be different the next time the Moon's cycle comes around to amplify tides again, in the mid-2030s, said the study.
“Global sea-level rise will have been at work for another decade. The higher seas, amplified by the lunar cycle, will cause a leap in flood numbers on almost all U.S. mainland coastlines, Hawaii, and Guam,” the study suggested.
Talking about the impact of HTF, Phil Thompson, an assistant professor at the University of Hawaii and the lead author of the study, said as 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,” he explained.