There is a Wobble in the orbit of the Moon. It’s not good.

© NASA / Earth Observatory
High tides will rise further as sea levels rise due to climate change. The moon’s 18.6-year “swing” will also affect the rising tides.

• High tides will rise further as sea levels rise due to climate change.
• The moon’s 18.6-year “swing” will also affect the rising tides.
• Altogether, these factors will result in more “nuisance flood” days per year.

Thanks to rising sea levels and an oscillation of the lunar orbit, the 2030s will be marked by a record number of high tide flooding around the U.S. coast, scientists warn in a new document.

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According to the US National Oceanic and Atmospheric Administration (NOAA), “nuisance flooding” occurs when the tides rise between 1.75 and 2 feet above the daily average high tide. These types of flooding may not be as extreme as those caused by hurricanes or other natural disasters, but they can still cause water to back up in basements and gurgling sewers.

NOAA reports that more than 600 harmful flooding occurred in the United States in 2019, and between May 2020 and April 2021, coastal communities experienced twice as many days of high tide flooding than 20 years ago. . But new research led by NASA, published last month in the journal Nature Climate Change– suggests that the trend will only increase in the 2030s.

© NOAA
floods at high tide are on the increase

Expect to see three to four times more flood days than today, all concentrated in a few months of activity each year. Flooding can even occur in clusters that last a month or more, leaving cities along the east and west coasts to deal with flooding every day or two, according to NASA.

“It is the effect accumulated over time that will have an impact,” said lead author of the study, Phil Thompson, assistant professor at the University of Hawaii, in a NASA press release. . “If there are 10 or 15 floods a month, a business cannot continue to operate with its parking lot underwater. People lose their jobs because they cannot get to work. become a public health problem. “

Climate change and the accompanying rise in sea level are only partly responsible. In fact, the main factor is an “oscillation” of the orbit of the moon that occurs regularly every 18.6 years. The oscillation is not new (it was first reported in 1728, according to NASA), but combined with the effects of climate change, it will create an unprecedented series of flooding at high tide.

© tide-forecast.com
Tide conditions for New York.

To understand the significance of this oscillation, let’s first develop the relationship of the moon to the ocean tides. The moon physically pulls the oceans by gravity (for this reason, the sun also affects the tides, although less noticeably), causing high and low tides. High tide, when the fluctuating ocean level is at its highest, can already cause problems in coastal cities. This can cause backflow in rivers that empty into the ocean, for example. Just check out the daily tide forecast for New York.

A few times a month, the high tides are made even higher by the combined factors of Earth, Sun, and the moon. These are called spring tides, and they also mean lower, more extreme low tides in both directions. But spring tides are just one way high tide varies over time, NASA explains.

Let us come back to this oscillation of the moon. The moon suppresses the tides on Earth for half of the 18.6 year cycle, which means high tides are below normal and low tides are higher than normal. But the other half of the time, the tides are amplified. We are currently in the last period of the moon cycle, but the sea level has not yet risen enough due to climate change to make the effect even worse.

Here is an extremely professional illustration of how this effect “stacks up” with the overall sea level during high tides:

© Caroline Delbert
An illustration shows compound curves affecting tide levels.

The next time we are on the amplified side of this lunar cycle, however, the combined rise in sea level and rising tides will cause a record number of harmful flooding along all of the continental United States, as well as the United States. ‘in Hawaii and Guam.

As an example, the new document highlights St. Petersburg, Florida, which is in the relatively lower Tampa Bay region. Researchers predict only six days of “minor flooding” per year between 2023 and 2033, a number that increases to 67 days per year between 2033 and 2043. For La Jolla, Calif., The number increases from one to 49 days per year . For Honolulu, Hawaii, this goes from two to 63 days per year.

© NASA
A diagram shows the combined effect of sea level rise and the moon’s oscillation on the tides in St. Petersburg, Florida.

By 2030, sea level will have risen by at least 1.4 inches, according to the Royal Society, the UK’s national academy of sciences. By 2039, that number will look more like 2.7 inches minimum. That, combined with the ripple effect, could leave seaside communities at odds with nature, requiring serious infrastructure changes. Hopefully stakeholders will take this new report seriously.

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