How rising sea-levels make days longer

The rotation of the Earth's core holds a clue to understanding global sea-level rise, scientists believe.

Scientists are studying changes in sea level in order to make accurate future predictions of the consequence of climate change, and are also looking down to the Earth's core to do so.

"Over the past 3,000 years, the core of the earth has been speeding up a little, and the mantle-crust on which we stand is slowing down," said Mathieu Dumberry from the University of Alberta in Canada.

As a consequence of the Earth rotating more slowly, the length of our days is slowly increasing.

In fact, a century from now, the length of a day will increase by 1.7 milliseconds. This may not seem like much, but Dumberry notes that this is a cumulative effect that adds up over time.

"In order to fully understand the sea-level change that has occurred in the past century, we need to understand the dynamics of the flow in the Earth's core" Dumberry explained.

The connection is through the change in the speed of the Earth's rotation.

The water melting from glaciers not only causes sea-level rise, but also shifts mass from the pole to the equator, which slows down the rotation.

The gravity pull from the moon also contributes to the slow down, acting a little like a leaver break.

"This can help to better prepare coastal towns, for example, to cope with climate change," Dumberry added.

The study was published in the journal Science Advances.