How the Moon ‘Wobbles’ Affects Rising Tides and Floods

The moon also revolves around the Earth about once a month, and this orbit is tilted a bit. To be more precise, the moon’s orbital plane around the Earth is at an inclination of about five degrees from the Earth’s orbital plane around the sun. (Here are some videos to illustrate this.)

Because of this, the trajectory of the moon’s orbit appears to fluctuate over time, completing a full cycle – sometimes referred to as a nodal cycle – every 18.6 years. “It’s happening on such a slow scale,” said Benjamin D. Hamlington, co-author of the article who leads the Sea Level Change team at NASA. “I think ‘precession’ is a more specific word than oscillation.”

At certain points in the cycle, the moon’s gravitational pull comes from such an angle that it pulls one of the two high tides of the day a little higher, to the detriment of the other. This does not mean that the moon itself is wobbling, nor that its gravity necessarily pulls our oceans more or less than usual.

“The focus on the nodal cycle is a little different from the message we were trying to get across,” Dr. Hamlington said. But he added that the phenomenon deserved attention.

Climate change-related high tide flooding is expected to break records with increasing frequency over the next decade, and people who want to accurately predict this risk have to work with a lot of noisy data including weather, events, etc. astronomical and regional variations in tides. .

The oscillation of the moon is part of this sound, but it has always maintained its own slow and steady rhythm.

“It just acts in the background when sea level rises,” said Brian McNoldy, senior associate researcher at the Rosenstiel School of Marine and Atmospheric School at the University of Miami.

“During its fastest rising phase, it acts to raise the effective sea level, and during its fastest descending phase, as we are now, it acts to suppress the effective sea level,” said said McNoldy, who wrote about the lunar node cycle but was not part of the Nature study. “It is not part of the sea level rise projections, because it is not a sea level rise; it’s just a swing.