Human activity is partly responsible for increasing a wobble in Earth's rotation, according to research published Monday.
Rising sea levels and melting Arctic ice are partly responsible for exacerbating Earth's wobble, NASA found after conducting a major study on the planet's rotation.
"In general, the redistribution of mass on and within Earth -- like changes to land, ice sheets, oceans and mantle flow -- affects the planet's rotation," NASA said in a statement.
As large bodies of mass -- such as ice sheets -- move, it can cause the planet to wobble as it rotates. This wobble may have shifted Earth's spin axis by more than 10 meters since 1899. Scientists say that this movement isn't anything unusual, though it's long been linked to natural phenomena like continental drift.
NASA's latest study confirmed that around a third of the Earth's wobble is indeed caused by the movement of land masses. Another third was attributed to activity in the mantle, an ever-moving layer of the planet that rests just below the crust. In particular, the study found that the wobble is exacerbated by the process of "mantle convection," where molten rock rises and falls in the mantle. NASA compared this process to the way boiling soup moves in a pot on a stove.
"As the pot, or mantle, heats, the pieces of the soup begin to rise and fall, essentially forming a vertical circulation pattern -- just like the rocks moving through Earth's mantle," NASA explained.
However, this subterranean movement is just part of the story.
According to NASA, ice loss in Greenland also played a key role in increasing Earth's wobble during the 20th century.
"In fact, a total of about 7,500 gigatons – the weight of more than 20 million Empire State Buildings – of Greenland's ice melted into the ocean during this time period," NASA stated.
"This makes Greenland one of the top contributors of mass being transferred to the oceans, causing sea level to rise and, consequently, a drift in Earth's spin axis."