NASA Scientists Identify Three Causes Of Drift In Earth’s Spin Axis

Posted: Sep 20 2018, 7:23am CDT | by , Updated: Sep 20 2018, 8:30am CDT, in Latest Science News


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NASA Scientists Identify Three Causes of Drift in Earth’s Spin Axis
The observed direction of polar motion (light blue line) compared with the sum (pink line) of the influence of Greenland ice loss (blue), postglacial rebound (yellow) and deep mantle convection (red). Credit: NASA/ JPL-Caltech

Using observational data from 20th century, researchers have for the first time identified three processes responsible for this drift.

Scientists have long known that Earth revolves around Sun. When Earth completes an orbit around sun or the star at the center of our solar system, it gives us an year. Our planet spinning around on its axis, an imaginary straight line that runs through the North and South Poles, gives us the length of a day (24 hours).

Although Earth’s rotation seems stable, it is actually far from being perfect. Earth drifts and wobbles when it rotates on its spin axis. This movement is known as polar motion and evidence suggest that the spin axis drifted about 4 inches (10 centimeters) per year in the 20th century. Over the course of a century, it becomes more than 11 yards (10 meters).

Using observational and model-based data from the 20th century, researchers have for the first time identified three processes responsible for this drift. They are Greenland ice loss, glacial rebound and mantle convection.

“The traditional explanation is that one process, glacial rebound, is responsible for this motion of Earth's spin axis. But recently, many researchers have speculated that other processes could have potentially large effects on it as well," said lead Surendra Adhikari of NASA's Jet Propulsion Laboratory in Pasadena. "We assembled models for a suite of processes that are thought to be important for driving the motion of the spin axis. We identified not one but three sets of processes that are crucial -- and melting of the global cryosphere (especially Greenland) over the course of the 20th century is one of them."

As Earth warmed in the 20th century, Greenland ice loss increased at an alarming rate. According to the latest study, a total of about 7,500 gigatons - the weight of more than 20 million Empire State Buildings - of Greenland's ice fell into the ocean during this time period. When a huge amount of mass transferred to the oceans, it caused a drift in Earth's spin axis.

The study also reveals that glacial rebound or the melting of heavy glaciers at the end of last ice age is responsible for only about a third of the polar drift in the 20th century. The third and final key contributor is mantle convection or the movement of tectonic plates on Earth's surface. It is triggered by the heat from Earth's core.

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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