# Idea about change in Earth's rotation speed by Climate Change

TheBigK1d
I know the two seem very unrelated at first, but actually I think the partial melting of the polar ice caps would actually give us longer days and nights.

Most of the ice that would be melting is relatively close to the poles, the axis of Earth's rotation. But, when it melted, the mass of the water would move closer to the equator, increasing the Earth's moment of inertia (I think this is the right way to use this, but basically the same as a figure skater moving their arms out and slowing their rotation speed down). Thus, the Earth's rotation speed would slow down, although probably so minuscule that it would only be measured by very precise instruments.

Do you guys think I'm right? And how would I calculate this speed change?

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## Answers and Replies

Mentor
Do you guys think I'm right? And how would I calculate this speed change?

You would estimate how significant it is by forming a rough estimate of the mass of the water that's moving from polar icecap to equatorial ocean, then comparing that mass with the mass of the Earth to see if it's enough to make a difference.

The mass of the Earth is about 6x1024 kilograms.

A volume of ice 1000 kilometers on a side and 100 meters thick will have a mass of about 1017 kilograms.

So the mass that we're shifting will be about one part in sixty million. You can play with the numbers a bit, move that sixty million around by a factor of ten or so in either direction... But you're still talking about an ant trying to influence the spin of a soccer ball by walking around on its surface.

Buckleymanor
Most of the ice that would be melting is relatively close to the poles, the axis of Earth's rotation. But, when it melted, the mass of the water would move closer to the equator, increasing the Earth's moment of inertia (I think this is the right way to use this, but basically the same as a figure skater moving their arms out and slowing their rotation speed down). Thus, the Earth's rotation speed would slow down, although probably so minuscule that it would only be measured by very precise instruments.
When the ice melted it would also move from a higher level on the Earth's surface to a lower one at first before moving towards the oblate equator.Which would speed up the Earth's rotation before any slowing.