Global Warming Shifts the Earth's Poles

ananyo writes "Global warming is changing the location of Earth's geographic poles, according to a study published this week. Researchers at the University of Texas, Austin, report that increased melting of the Greenland ice sheet — and to a lesser degree, ice loss in other parts of the globe — helped to shift the North Pole several centimeters east each year since 2005. From 1982 to 2005, the pole drifted southeast towards northern Labrador, Canada, at a rate of about 2 milliarcseconds — or roughly 6 centimetres — per year. But in 2005, the pole changed course and began galloping east towards Greenland at a rate of more than 7 milliarcseconds per year (abstract). The results suggest that tracking polar shifts can serve as a check on current estimates of ice loss. Scientists can locate the north and south poles to within 0.03 milliarcseconds by using Global Positioning System measurements to determine the angle of Earth's spin. When mass is lost in one part of a spinning sphere, its spin axis will tilt directly towards the position of the loss — exactly as the team observed for Greenland."

Three Gorges Dam

[ShanghaiBill]

Part of this shift could be caused by filling the reservoir behind the Three Gorges Dam, since that is on the opposite side of the world from Greenland. But that would only explain part of it, since the reservoir holds about 40km^3 and Greenland is losing about 240km^3 per year.

Re:The opposite might also be true

[ZaMoose]

I was actually going to post something incredibly close to this. The causal link just isn't there, as far as I can tell. It could very well be that the glaciers melt/freeze due to slight shifts in the poles' positions and variations in the Sun's output.

Spinny-Chair

[Mystakaphoros]

Is this a conservation of angular momentum thing? Because I feel like my high school physics teacher would try to explain this by spinning someone around in a chair with a melting ice cube on their head.

GPS reference system

[XNormal]

I wonder how this affects high-accuracy geodetic GPS measurements. The GPS coordinate system is defined by the Earth's axis.

Re:GPS reference system

[Maximum Prophet]

If you had a run of the mill GPS system, and you drove your car very, very, far North, eventually you'd lose signal.

What I imagine is going on here, is that there is a ring of base stations watching the GPS satellites around each pole. If you know the base stations haven't moved w.r.t. the pole, then you can calculate where the center of spin is, thus where the pole is.

Re:WTF? has been happening for years

[dargaud]

You are talking about the magnetic pole (which wanders a lot, and may or may not shift in the coming millenia, not decades as you state) while the article is about the geographic pole which is the axis of rotation of the mound of dirt and water we call Earth. And it's also different from the precession of the equinoxes which also cycles in about 26000 years (changing the polar star to something different than the current Polaris).

Re:Three Gorges Dam

[bmo]

A nautical mile isn't an "imperial unit"

It's a nautical unit. It's actually Babylonian. It's useful for measuring the Earth because it's "close enough" to a minute of arc.

If Gunther had changed his surveyor's chain to 1/100 of a nautical mile in 1620, (instead of 1/80'th statute mile)^1 we wouldn't be talking about the Meter at all, as it would have been useless.

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BMO

1. A nautical mile is 92.06 chains. An adjustment of the chain to 100 per NM wouldn't have been a big difference, and made things even easier for surveyors and engineers.