Melting polar ice caps affect Earth’s wobble

Lawrence Goodwyn

The “Wobble” was a trend that swept across dance floors in 2008. Around the same time, geologists realized their own wobble was changing dramatically due to climate change. 

Sea levels on Earth are increasing, which is redistributing the mass of the Earth and causing a subtle eastern shift of the North Pole toward Greenland. This shift affects Earth’s wobble, which is the rate at which Earth’s rotational speed deviates from the average speed. 

The Earth’s rotational speed and axis should be constant, but due to normal disturbances — such as precipitation, melting ice and atmospheric pressure changes — the rotational axis is not stationary, which causes the Earth’s wobble. This axis is changing more quickly than it has before. 

Jianli Chen, senior research scientist at the Center for Space Research, and UT geology professor Clark Wilson were part of the first team to realize what was causing the changes in the wobble.

Due to the spinning of the Earth and its large mass, the axes of Earth move. With the movement of the axes, Earth’s poles move too in a phenomenon called polar motion.

Polar motion comes from three factors: the annual wobble, Chandler wobble and linear drift. The annual wobble and Chandler wobble are changes in Earth’s spin frequency that repeat regularly with known speeds. 

The linear drift of the Earth is not predictable. It describes the net movement of the poles and emerges after decades of wobbles, according to Chris Linick, an aerospace engineering graduate student.  

Most changes in the Earth happen slowly — they take hundreds of millions of years. However, the dramatic deviations in the wobble have occurred in the last decade and a half, according to Chen. 

“The recent shift from the 20th-century direction is very dramatic,” NASA postdoctoral fellow Surendra Adhikari said to the Guardian.

It was apparent that a factor in the drift was coming from climate change — the melting ice caps, according to Chen. 

Individuals on Earth can’t feel the changes in the wobble, but precise measurements can measure the movement, according to Chen. 

UT’s G.R.A.C.E. satellite measures the mass distribution of Earth every month, revealing regions of mass loss and gain. From the satellites’ results, scientists were able to identify that more mass was accumulating in Greenland. From their calculations, they were able to determine that melting ice was a large factor in the movement of the pole. 

The researchers’ results were brought back to light when Adhikari at NASA’s Jet Propulsion Lab confirmed their findings from 2013. He stated a major part of the mass redistribution was, in fact, from contemporary ice mass loss, according to Science Advances. 

The scientists are still in consensus that these changes are not directly a cause for concern.

“If the ice caps melt completely, then the resulting polar shift will have a miniscule climate impact compared to the consequences of total ice loss,” Linick said. “For example, if the Antarctic ice sheet were to melt suddenly and completely, then Earth’s rotation axis would pierce the surface only a half mile from where it is today, but mean sea level would rise by roughly 190 feet.”