As if we didn’t already have enough to worry about….
Excerpts from the New Scientist
Warming oceans could cause Earth’s axis to tilt in the coming century, a new study suggests. The effect was previously thought to be negligible, but researchers now say the shift will be large enough that it should be taken into account when interpreting how the Earth wobbles.
The Earth spins on an axis that is tilted some 23.5° from the vertical. But this position is far from constant – the planet’s axis is constantly shifting in response to changes in the distribution of mass around the Earth. “The Earth is like a spinning top, and if you put more mass on one side or other, the axis of rotation is going to shift slightly,” says Felix Landerer of NASA’s Jet Propulsion Laboratory in Pasadena, California.
The influx of fresh water from shrinking ice sheets also causes the planet to pitch over. Landerer and colleagues estimate that the melting of Greenland’s ice is already causing Earth’s axis to tilt at an annual rate of about 2.6 centimetres – and that rate may increase significantly in the coming years.
Now, they calculate that oceans warmed by the rise in greenhouse gases can also cause the Earth to tilt – a conclusion that runs counter to older models, which suggested that ocean expansion would not create a large shift in the distribution of the Earth’s mass.
The team found that as the oceans warm and expand, more water will be pushed up and onto the Earth’s shallower ocean shelves. Over the next century, the subtle effect is expected to cause the northern pole of Earth’s spin axis to shift by roughly 1.5 centimetres per year in the direction of Alaska and Hawaii.
The effect is relatively small. “The pole’s not going to drift away in a crazy manner,” Landerer notes, adding that it shouldn’t induce any unfortunate feedback in Earth’s climate.
And climate change can also affect the Earth’s spin. Previously, Landerer and colleagues showed that global warming would cause Earth’s mass to be redistributed towards higher latitudes.
Journal reference: Geophysical Research Letters (in press)
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