In the mid-2030s, many coastal cities in the United States will experience an increase in high-tide floods, notes a new study by NASA researchers. The team writes that a lunar wobble will amplify the rising sea levels caused by the ongoing climate change.
Several US coastal cities have already witnessed high-tide floods, with the National Oceanic and Atmospheric Administration (NOAA) reporting over 600 such floods in 2019. The new study, which looked at astronomical causes of flooding, noted that the alignment of rising sea levels with the lunar cycle will cause a dramatic increase in these numbers. The results were published in Nature Climate Change.
NASA Administrator Bill Nelson explained in a release: “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. NASA’s Sea Level Change Team is providing crucial information so that we can plan, protect, and prevent damage to the environment and people’s livelihoods affected by flooding.”
NASA added that the moon’s wobble is not a new or dangerous thing and 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,” notes the release.
The wobble in the moon’s orbit takes about 18.6 years to complete. In the first half of the cycle, Earth’s regular daily tides are suppressed and in the second half, the tides are amplified. In the mid 2030s when the moon comes in the tide-amplifying part of the cycle, it will have an effect on the already high global sea level and cause flooding on almost all US mainland coastlines, Hawaii, and Guam.
Phil Thompson, an assistant professor at the University of Hawaii and the lead author of the study, pointed out in a release 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.”
“From a planning perspective, it’s important to know when we’ll see an increase. 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.” explains Ben Hamlington, a co-author of the paper. He is the leader of NASA’s Sea Level Change Team.