Earth's Rotation & Global Agriculture: Impact & Possibilities

[imotta]

How much will this phenomenon affect the Earth's rotation? Is it possible that the change in the Earth's rotation movement will significantly affect agricultural production on a global scale, for example?

 

[jbriggs444]

How much will this phenomenon affect the Earth's rotation? Is it possible that the change in the Earth's rotation movement will significantly affect agricultural production on a global scale, for example?

You are suggesting that the migration of fluid from the polar ice cap to the oceans will make the Earth "shorter and fatter", thus slowing its spin rate? And that the resulting change in day length will affect agriculture?

Have you calculated how much change in day length would result from moving the [south] polar ice cap to the equator? Make some generous assumptions and see what you get.

 

[Baluncore]

As the Antarctic ice cap melts it will distribute it's mass equally over the oceans. The moment of inertia of the Earth will change as the mass of the ice is redistributed from a disk near the axis to a spherical shell over the oceans.

Conservation of angular momentum will slow the Earth. The day will lengthen by less than a second, but sundials will also slow down to fully compensate.

The main change that people and their economy will have is sea level rise, firstly because of the melt water, and secondly because of the thermal expansion of the water column happening at the same time due to the warming that melts the ice. The coastal regions and many major cities will be drowned long before anyone notices the solar days are very slightly longer. So yes, the Earth will slow, the days will lengthen, but you will certainly not notice it without an atomic clock.

NASA write; “For example, if the Greenland ice sheet were to completely melt and the meltwater were to completely flow into the oceans, then global sea level would rise by about seven meters (23 feet) and the Earth would rotate more slowly, with the length of the day becoming longer than it is today, by about two milliseconds”.
https://climate.nasa.gov/faq/30/if-...an-what-would-happen-to-the-planets-rotation/

 

[Keith_McClary]

Have you calculated how much change in day length would result from moving the [south] polar ice cap to the equator?

I calculated

Was the filling of the Three Gorges Dam's impact on the Earth's rotation rate detectable?​

For the polar cap, aproximate $cos L = 0$ and $m=2.65 \times 10^{19}$, so the fractional change in moment of inertia is
$$\frac{mR^2}{I}( \frac{2}{3})
= \frac{2.65 \times 10^{19} \times(6.37 \times 10^{6})^2}{8.04×10^{37}}(\frac{2}{3}) = 8.9 \times 10^{-6}$$
which is also the fractional decrease in rotation rate.