Coastal communities, from the Jersey Shore to Miami to Southern California, are likely to see a dramatic increase in high tide flooding beginning in the mid-2030s as rising sea levels sea due to climate change is aligning with natural changes in the moon’s orbit, a new NASA study warns.
High tide flooding, also known as nuisance flooding or sunny weather flooding, does not occur from storm surges due to extreme weather or excessive rainfall, but rather when the tide rises in populated areas. Flooding can overwhelm storm sewers, close roads and compromise infrastructure over time.
These types of floods are already familiar to residents of places like Stone Harbor, New Jersey, or Miami, Florida, and the new study shows that sunny weather flooding will increase in frequency in the mid-2030s.
David Velinsky, vice president of science at Drexel University’s Academy of Natural Sciences, who has studied the effects of sea level rise on coastal marshes in New Jersey and Delaware, said that the new study was concerning for coastal communities.
“Sea level rise will continue more and more, and we will lose more marshes. Coastal forests will be impacted, and we see these changes happening in the coming decades,” said Velinsky, who is also head of the Drexel department. Biodiversity, Earth and Environmental Sciences. “And the question is how are we going to deal with it? How are the coastal areas going to deal with it?”
Velinsky said the study was illuminating because it looked closely at historical data from 89 sites in every coastal US state except Alaska.
“Planning, adaptation and even environmental justice issues should have started years ago,” he added.
High tide floods are visually less dramatic and involve less water than hurricane storm surges, so they are often seen as a less urgent problem.
“But if there’s flooding 10 or 15 times a month, a business can’t continue to operate with its parking lot underwater,” said University of Hawaii assistant professor and lead author Phil Thompson. of the NASA study. “People lose their jobs because they can’t get to work. Leaking cesspools become a public health problem.
The extreme floods predicted in the new study are due to a so-called “wobble” in the moon’s orbit. The oscillation occurs on an 18.6 year cycle and is completely natural, first discovered in 1728.
But the new development of sea level rise, as global temperature warms due to human-induced climate change, amplifies one of the effects of the wobble.
The moon’s gravitational pull is the cause of the daily high and low tides. But Earth’s regular high and low tides change with the moon’s wobble.
During the first half of the nearly 19-year cycle, the tides are suppressed: high tides are lower and low tides are higher. In the other half of the cycle, the tides are amplified, with higher high tides and lower low tides.
High sea levels push all high tides higher, so when the next 18.6-year moon swing cycle amplifies high tides, they will regularly exceed flood thresholds.
As a result, high tides will more often exceed known flood thresholds across the country.
The floods will also occur in clusters, which could last a month or more at a time depending on the position of the moon, sun and Earth, NASA said.
As the moon and earth align with each other and the sun in specific ways, some city dwellers might see flooding every day or two.
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Ben Hamlington, co-author of the moon wobble study and leader of NASA’s sea level change team, said the study is vital for coastal planners, who can tend to focus on preparing for extreme weather events versus chronic flooding.
“From a planning perspective, it’s important to know when we’ll see an increase,” Hamlington said. “Understanding that all of your events are clustered in a particular month, or that you might have more severe flooding in the second half than the first – that’s helpful information.”
The moon is currently in the tide-boosting part of its 18.6-year swing, in 2021. But most U.S. coastlines haven’t yet seen enough sea level rise to notice the effects of flooding. .
By the mid-2030s, the next time the oscillation enters its tidal amplification phase, global sea level rise due to climate change will have had another decade to advance.
The problem will occur around the United States, not just on one coast or the other, with “a jump in the number of floods on almost all continental United States coasts, Hawaii and Guam”.
Far northern coastlines, like Alaska’s, “will be spared for another decade or more because these land areas are expanding due to long-term geologic processes,” NASA said.
The study projected the results out to 2080 by mapping “scenarios of sea level rise and flood thresholds widely used by NOAA, the number of times these thresholds were exceeded each year, the astronomical cycles and statistical representations of other processes, such as El Niño events, which are known to affect tides.
NASA’s Sea Level Portal will be updated with the study results as a resource for policymakers and the public.
Velinsky, the Drexel scientist who teaches an oceanography course, said he would incorporate the moon’s “wobble” effect in the future.
“I’m going to include it next time because it’s going to have a global impact,” he said.