Melting glaciers have shifted the Earth’s axis

Melting glaciers have shifted the Earth’s axis

In the 1990s, the Earth’s axis underwent a major change. It is normal for the Earth’s axis to move a few centimeters each year. But, in the 1990s, the direction of the polar drift suddenly changed and the pace of the drift accelerated. The reason for this sudden change was previously unclear, but a team of scientists from Beijing recently published an article that shows that the main driver behind the change in the direction of axial displacement was the melting of glaciers caused by global warming.

The Earth seen from a satellite. Source: NASA / Goddard Flight Center

The axis of rotation of the Earth is the figurative line around which the Earth rotates. The poles, north and south, are located at each end of the axis of rotation. In contrast, magnetic poles – the ones you can find using a compass – are usually offset from the geographic poles, and their location moves with the magnetic field.

“The Earth spins around its axis a bit like a top,” Suxia Liu explained in an interview with GlacierHub. “If the weight of one area is shifted to another area, the router will begin to tilt, causing a change in the axis of rotation.” Liu co-edited the article with his colleague Shanshan Deng from the Chinese Academy of Sciences.

Bernhard Steinberger, a researcher at the GFZ German Research Centers for Geosciences who did not work on this article, explained how glaciers influence mass distribution. “The Earth always orients itself with respect to the pole in such a way as to move the masses as far as possible from the pole,” he wrote in an interview with GlacierHub. “For example, if there is a glacier growing in Greenland, the orientation of the Earth will change so that Greenland will be further from the Pole. If a glacier melts in Greenland, it would change in the opposite direction. “

Before anthropogenic forces, the main drivers of polar drift were ocean currents and the movements of molten rock deep below the Earth’s surface. The research team reanalyzed existing data to determine what role terrestrial water storage – how water is dispersed over the Earth’s surface and into oceans and groundwater – played in this. change. They determined that the main driver of the change in direction was the melting of the glaciers and the resulting change in mass distribution.

Most of the world’s glaciers are above ground, and when these glaciers melt, the water they contain moves through bodies of water. “Shifting water storage away from aerial glaciers in one area of ​​the Earth’s surface to another results in a polar shift due to the change in weight,” Liu said.

An icy white expanse is dotted with puddles of bright blue water.

An aerial view of the Greenland ice cap is dotted with “lakes” of blue meltwater. Source: Bernt Rostad / Flickr

In 1995, the direction of the planet’s polar drift suddenly shifted from south to east. Today, scientists can connect polar drift to glacier loss using gravitational data from NASA’s twin GRACE (Gravity Recovery and Climate Experiment) satellites, launched in 2002. However, as the satellites had not yet launched in the 1990s, researchers had to piece together the reasons for the sudden change in direction without these detailed gravitational records.

Besides the greenhouse gas emissions that cause glaciers to melt, other human activities are responsible for changes in the earth’s hydrosphere. The team also found that groundwater pumping was and continues to be a polar drift factor. Pumping groundwater for drinking water, irrigation, and manufacturing has been common practice since the 1960s. The United States alone uses 82.3 billion gallons of groundwater every day. Water that is removed from the subsoil ends up in the atmosphere as it evaporates from irrigated crops or in the ocean as runoff from irrigation systems to rivers, redistributing mass around the world and changing the pattern. rotation of the planet.

Large white and blue tipped pipes plunge into dusty brown ground.A groundwater pumping station in the Central Valley of California. Source: Chris Austin/ Flickr

As Earth’s glaciers recede at an unprecedented rate, the mass of the planet is constantly redistributed. The team’s results suggest that we can expect the hydrosphere to continue to cause the Earth’s axis to shift in the years to come.

Although imperceptible to humans without the use of specialized instruments, the enormous mass of the Earth has changed more than ever. Since 2005, the rate of polar drift has increased by about four centimeters per year. “Change is nothing that an ordinary person notices in their day-to-day life,” said Steinberger. “You would really have to wait millions of years to notice anything.” It is, however, a stark reminder of the magnitude of the effects humans have on the planet.



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