07/23/2021 at 1:00 p.m. CEST
Climate change and the Moon will lead to an increase in coastal flooding from the 2030s. This is the conclusion of a study conducted by NASA and the University of Hawaii, which reveals that high tides will more frequently exceed known flood thresholds around the world.
High tide flooding is already a problem in many coastal cities around the world. The National Oceanic and Atmospheric Administration recorded a total of more than 600 such floods in 2019 in the United States.
However, from the mid-1930s onwards, aligning sea level rise with a lunar cycle will start to hurt coastal cities. a decade of dramatic increase in the number of floodsaccording to the study, which takes into account all known oceanic and astronomical causes of flooding.
Research results indicate that flooding will sometimes occur in clusters for a month or more, depending on the positions of the Moon, Earth and Sun. “When the Moon and Earth are specifically aligned with each other and with the Sun, the resulting gravitational pull and the corresponding response from the ocean can cause city dwellers to cope. flooding every day or every other day& rdquor ;, alert from NASA.
“Low areas near sea level are increasingly threatened and they are suffering from increased flooding, and will only get worse, ”said NASA Administrator Bill Nelson.
“The combination of the Moon’s gravitational pull, sea level rise and climate change will continue to exacerbate coastal flooding on our coasts and around the world,” he said.
Crucial information to prevent damage
Crucial information to prevent damage“NASA’s Sea Level Change team provides crucial information so that we can plan, protect and prevent damage to the environment and to the livelihoods of those affected by the floods, ”adds Nelson.
“It is the cumulative effect over time that will have an impact,” says Phil Thompson, professor at the University of Hawaii and lead author of the study, published in “Nature Climate Change”.
Since flooding at high tide involves a small amount of water compared to storm surges, there is a tendency to view them as a lesser problem overall, notes Thompson.
“But if it floods 10 or 15 times a month, a business cannot continue to operate with its underwater parking lot. People are losing their jobs because they cannot go to work. And the sumps that infiltrate become a public health problem, ”he explains.
Why will there be more flooding? The main reason, according to the researchers, is a “regular oscillation in the orbit of the moon which takes 18.6 years to complete & rdquor ;.
There is nothing new about this oscillation, which was first recorded in 1728. What is dangerous is how one of its effects on the gravitational pull of the Moon, the main cause of tides on Earth, will combine with rising sea levels as a result of global warming.
In the middle of this 18.6-year lunar cycle, Earth’s regular daily tides are suppressed: high tides are below normal and low tides are higher than normal. In the other half of the cycle, they are amplified: high tides rise, and low tides, fall even more.
High tides, always higher
High tides, always higherSometimes the global rise in sea level due to climate change pushes high tides in one direction only: upwards. Thus, “half of the 18.6-year lunar cycle counteracts the effect of rising sea levels at high tide and the other half enhances the effect,” says NASA.
The Moon is now in the tidal amplifying part of its cycle. However, along most of the coasts of the United States, sea levels have not risen enough that, even with this lunar “push”, high tides regularly exceed flood thresholds.
The story will be different the next time the cycle boosts the tides again, in the mid-2030s, scientists predict.
“Global sea level rise due to climate change will continue for another decade. A higher sea level, amplified by the lunar cycle, will lead to an increase in the number of floods on most of the mainland coasts of the United States, Hawaii and Guam.
Alaska will be spared another decade from flooding
Only the coasts of the Far North, including Alaska, will be spared for another decade or more as these land areas increase due to long-term geological processes, ”says NASA.
Ben Hamlington of NASA’s Jet Propulsion Laboratory (JPL) in Southern California, co-author of the article and leader of the agency’s Sea Level Change team, notes that the study’s results are a “resource. vital & rdquor; for coastal planners, they can “prepare for extreme events instead of more flooding at high tide”.
“Realize that all events are grouped together in a particular month, or that you might have more severe flooding in the second half of the year than in the first; this is useful information, ”he emphasizes.
A high tide flood tool developed by Thompson already exists on the NASA team’s Sea Level Portal, a resource for policymakers and the general public. The coastal flooding tool will be updated in the near future based on the results of this study.
NASA Sea Level Change Simulator: https://vesl.jpl.nasa.gov/
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