Global Geological And Climatic Events

How the Moon ‘Wobble’ affects rising tides


From UPSC perspective, the following things are important :

Prelims level: Moon wobble

Mains level: Moon wobble and climate change

US coastlines will face increasing flooding in the mid-2030s due to a regular lunar cycle called the wobble effect that will magnify rising sea levels caused by climate change.

What is the Moon Wobble?

  • The moon wobble is nothing but a regular swaying in the moon’s orbit.
  • It was first documented way back in 1728.
  • This wobble takes over an 18.6-year period to complete and continues in a cyclic fashion.

How does this wobble occur?

  • High tides on this planet are caused mostly by the pull of the moon’s gravity on a spinning Earth. On most beaches, you would see two high tides every 24 hours.
  • The moon also revolves around the Earth about once a month, and that orbit is a little bit tilted.
  • moon’s orbital plane around the Earth is at an approximate 5-degree incline to the Earth’s orbital plane around the sun.
  • Because of that, the path of the moon’s orbit seems to fluctuate over time, completing a full cycle — sometimes referred to as a nodal cycle — every 18.6 years.
  • At certain points along the cycle, the moon’s gravitational pull comes from such an angle that it yanks one of the day’s two high tides a little bit higher, at the expense of the other.
  • This does not mean that the moon itself is wobbling, nor that its gravity is necessarily pulling at our oceans any more or less than usual.

What impact does this wobble have on Earth?

  • Influences the ebb and flow of tides: The moon wobbles impacts the gravitational pull of the moon, and therefore, indirectly influences the ebb and flow of tides here on the Earth.
  • One half of the 18.6-year cycle suppresses the tides, which means that the high tides get lower, while the low tides get higher than normal.
  • Once this cycle completes, the situation flips—in the subsequent cycle, the tides are amplified, with high tides getting higher and low tides, lower.
  • The lunar cycle is expected to shift again by mid-2030, and in the coming phase, the tides will amplify once again.

Moon wobble and climate change

  • The upcoming changes in the lunar cycle will pose a serious threat, as the amplified high tides coupled with the rising sea levels will make the risk of flooding far greater across all coastal regions of the globe.
  • The study predicts that the high tide-associated floods—also known as nuisance floods or sunny day floods—may occur in clusters that could last for months or even for longer periods!
  • This surge will be closely associated with the position of the Moon, Earth and the Sun.
  • When the Moon and Earth line up in specific ways with each other and the Sun, the resulting gravitational pull and the ocean’s corresponding response may leave city-dwellers coping with floods every day or two.

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