NASA determines why the Earth is wobbling on its axis

We all know the basic properties of the rotation of the Earth. It runs completely every 24 hours, and we call it a day. You may not be aware that the earth is flickering slightly, causing a few centimeters a year. NASA said it has now identified three causes for this change. As expected, the loss of polar ice is a major factor.

During the 20th century, scientists watched with fascination the axis of the Earth oscillate several meters. On average, it drifts about 10 centimeters. Sometimes it was less, and sometimes more. In the year 2000, the axis moved by 7 inches. During the 20th century, the axis migrated about 10 meters in total. But why?

NASA has used observational data and data based on recent decades' models to determine once and for all the factors that affect the planet's oscillation. It has landed on three main causes: loss of ice mass, glacial rebound and convection of the mantle.

Ice loss is easy to visualize. As the ice caps melt, the mass is transferred from the polar regions into the ocean. NASA says that Greenland is the main culprit here. It's a little further south, so it lost a lot of ice over the last century – about 7,500 gigatons. It's about the same as 20 million Empire State Buildings. This causes about a third of the oscillation.

The observed direction of polar motion, represented by a light blue line, compared to the sum (pink line) of the influence of Greenland ice loss (blue), postglacial rebound (yellow) and deep mantle convection (red). The contribution of mantle convection is very uncertain.

The rebound of glaciers is linked to the loss of ice, but the mechanism by which it affects the oscillation of the Earth is different. As the glaciers retreat, they reveal a long compressed soil that is suddenly cleared by ice. This soil slowly rises to its natural level, which changes the distribution of the mass and affects the oscillation. NASA says that this is also responsible for about a third of the flicker.

The last third comes from the convection of the mantle. This is why the tectonic plates move during the eons. When the molten rock moves into the mantle, it slightly changes the balance of the planet, which adds to the axial shift. So, this part of the flicker is definitely not the fact of humanity.

With the identified causes, scientists can track the polar movement and understand what changes are due to human activity and are a consequence of the nature of the Earth. We can also predict how the oscillation will change in the future as warming and polar ice loss increases.

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