Melting Ice Caps and Day Length
Country: United States
Date: July 2006
If the polar ice caps melted, how might this effect
the length of a day?
Well, the north polar ice cap would not have much effect, because it
is floating sea ice. The ice caps that would matter are the
Antarctica and Greenland ice caps. If they were to melt, days would
get slightly longer (and there would be slightly fewer of them in a
year). This is because the liquid water would distribute more
evenly about the globe rather than all being near the poles, so the
Earth's moment of inertia would increase. Since the Earth's angular
momentum will not change, that means that its angular velocity (rate
of turning) will decrease.
This is analogous to what happens on a playground carousel when a
person standing near the axis moves outward: the rotation will slow.
This will be a very small change, as the mass of water in the polar
ice caps is only a teeny tiny fraction of the total mass of the Earth.
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Update: June 2012