North Pole Moves as Ice Sheets Melt

A true-color image taken on May 5, 2000, by an instrument aboard NASA's Terra spacecraft, over the North Pole, with sea ice shown in white and open water in black. (Image credit: Image by Allen Lunsford, NASA GSFC Direct Readout Laboratory; Data courtesy Tromso receiving station, Svalbard, Norway)

The North Pole’s surprise trip toward Greenland is due to Earth's rapidly melting ice sheets, a new study finds.

The distribution of mass across the planet determines the position of Earth's poles. Because Earth is a bit egg-shaped, the North Pole is always slightly off-center. It's also been slowly drifting south, responding to long-term changes since the last Ice Age, as the enormous ice sheets that once covered large swaths of the planet melted and parts of the Earth rebounded from the lost weight.

Melting ice moves mass around by adding water to the oceans and lightening the load on ice-covered crust. Although global ice melt plays a role in the pole's shift, Greenland itself is the primary contributor to the eastward movement, the researchers found. "Both of [those factors] are contributing, but now we can say glacial melting in Greenland produces an observable polar motion," said Clark Wilson, a study co-author at the University of Texas, Austin.

The change is small, dwarfed by the pole's broad wandering circles, which are caused by Earth's bulging midriff (the 14-month Chandler wobble) and an annual wobble related to seasonal shifts. However, "if you remove those effects, you'll see a long-term drift," Wilson told LiveScience.

Using data from NASA's GRACE satellite, which measures Earth's gravity field, the researchers tested whether Greenland's ice loss changed the pole position. The data can track how water and ice shift across the planet. "Mass is moving around all the time," Wilson said.

Knowing the precise location of the North Pole has become a critical part of modern life. It's the foundation of GPS, which guides people with mapping apps, as well as military systems and planes.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on LiveScience.com.

Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.