Earth wobbles as its axis rotates, and NASA understands why

Rising temperatures in the 20th century caused melting ice in Greenland. The researchers say that 7,500 gigatonnes of ice, the weight of more than 20 million Empire State Buildings, melted in the ocean during this period.

Melting ice, combined with Greenland's position on Earth, plays a role in the way the Earth is shaking. "There is a geometric effect that if you have a mass of 45 degrees relative to the North Pole – what Greenland is – or the South Pole, it will have a greater impact on the axis of rotation of the Earth Pole", said Eric Ivins, a research scientist at the Jet Propulsion Laboratory and co-author of the study, in a statement.

Several studies have suggested that global warming has contributed to an increase in ice melt in Greenland, Antarctica and other parts of the world. A February study indicated that sea level could be at least two feet higher at the end of the century than it is now due to melting ice.

Last month, scientists observed that some of the oldest and thickest ice in the Arctic, north of Greenland, showed signs of the beginning of a breakup.

Another factor noted by researchers is the rebound of glaciers, a process in which lands once depressed by heavy glaciers begin to rise. The circulation of matter within the Earth's mantle, called mantle convection, also plays a role.

Ivins and lead author Surendra Adhikari said that these three factors contributed to a significant redistribution of the land mass, causing a flickering effect.

"The traditional explanation is that a process, the glacial rebound, is responsible for this movement of the axis of rotation of the Earth," said Adhikari. "But recently, many researchers have speculated that other processes could have potentially significant effects on it as well."