The shift in the Earth's axis is man-made
Since the 1990s, researchers have observed a shift in the Earth's axis of rotation of around 80 centimetres. The question was why. The main reason is climate change - the melting of the polar ice sheet and mountain glaciers and the associated rise in sea levels. However, this alone does not fully explain it. A team of scientists led by South Korean geophysicist Ki-Weon Seo from Seoul National University has now calculated in a study that human groundwater extraction for irrigation has also contributed to this. He reported this in the journal "Geophysical Research Letters". The extracted groundwater also flows into the world's oceans and leads to an increase in sea level and thus also to a shift in the Earth's axis.
According to this study, an important anthropogenic contribution is the rise in sea level, which is due to the depletion of groundwater as a result of irrigation. According to Ki-Weon Seo, a climate model estimate for the period 1993-2010 shows a total groundwater depletion of 2,150 GTon, which corresponds to a global sea level rise of 6.24 millimeters. However, direct observations to support this estimate have been lacking until now. In this study, the researchers show that the model estimate of water redistribution from the aquifers to the oceans would lead to a shift of the Earth's rotation pole by 78.48 centimetres in the direction of 64.16°E.
"I am very happy to have found the unexplained cause of the rotational pole drift. On the other hand, as a resident of the Earth and a father, I am concerned and surprised that groundwater pumping is another cause of sea level rise."
Ki-Weon Seo
Asked about this by ntv, Harald Schuh from the German Research Center for Geosciences GFZ in Potsdam said that the new calculation of the pole shift is "absolutely plausible and correct". "Nowadays, it is possible to measure the current position of the pole to an accuracy of less than one centimeter and thus also identify long-term pole movements, as in the aforementioned study," he continued.
Groundwater extraction in the mid-latitudes has a major impact
According to the authors of the study, the redistribution of groundwater from the mid-latitudes has a particularly large impact on the North Pole. During the study period, the greatest groundwater loss occurred in large areas in western North America and north-western India, both of which are located in mid-latitudes.
Back in 2021, a Chinese research team led by Shanshan Deng from the Chinese Academy of Sciences in Beijing discovered that the melting of the glaciers led to a change in the Earth's axis, or more precisely: it tilted in a different direction. They presented their findings in March 2021 in the journal "Geophysical Research Letters" .
The real pole migration
The Earth's axis moves back and forth over the course of a year - about ten centimetres. These fluctuations are known as true polar drift and are normal. Since the 1990s, scientists have observed that the drift is moving in the opposite direction - by around ten degrees to the east. "The faster melting of ice masses as a result of global warming was the most likely cause of the change in polar drift in the 1990s," says Deng.
