The Earth is growing more spherical because 20,000 years ago we had a lot more ice at the poles. When ice sheets were at the poles they kind of squished the Earth from both poles and the Earth flattened a little bit. When those ice sheets melted, that flattening started to rebound and we’re becoming spherical, so our spin rate should be increasing, like a ballerina or a figure skater. The ice age correction is a speeding up of the rotation rate.
Is water moving off glaciers, slowing the Earth’s rotation, this time analogous to a figure skater putting arms out?
Right. Glaciers are mostly near the axis. They’re near the North and South Poles and the bulk of the ocean is not. In other words, you’re taking glaciers from high latitudes like Alaska and Patagonia, you’re melting them, they distribute around the globe, but in general, that’s like a mass flux toward the equator because you’re taking material from the poles and you’re moving it into the oceans. That tends to move material closer to the equator than it once was.
*So the melting mountain glaciers and polar caps are moving bulk toward the equator?
Yes. Of course, there is ocean everywhere, but if you’re moving the ice from a high latitude and you’re sticking it over oceans, in effect, you’re adding to mass in the equator and you’re taking mass away from the polar areas and that’s going to slow the earth down. That’s the calculation we did. We also computed how those glaciers would affect the orientation of poles. In both cases, when you do that calculation and you compare it to this ice age corrected satellite and astronomical observations, you fit them precisely.
What we showed in this recent paper is that when you look at the modern data on rotation and you correct for ice age, you have a leftover, and that leftover is precisely what it should be if it were due to the kind of melting that global change scientists believe happened in the 20th century.
Related: [[Jerry Mitrovica]] [[../www/climate change]] Source: Oceans on Nautilus: Why Our Intuition About Sea-Level Rise Is Wrong
source:: [[nautil.us]] #climate-change