A new study has revealed that the axis of the Earth’s rotation has shifted because of extreme extraction of groundwater for drinking or agricultural purposes. The research paper has recently been published in the Geophysical Research Letters journal.

As per the study paper titled ‘Drift of Earth’s Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993-2010’, human beings extracted nearly 2,150 gigatonnes of groundwater between 1993 and 2010. It may be noted that one gigatonne is equal to one billion metric tonnes or 1,000,000,000,000kg. Researchers are of the opinion that the Earth’s axis is moving eastward by 4.36cm every year due to this huge amount of groundwater extraction.

Scientists from different parts of the globe are involved in this research. They include Ki-Weon Seo, Taewhan Jeon, Jae-Seung Kim and Kookhyoun Youm of the Seoul National University (South Korea), Dongryeol Ryu of the University of Melbourne (Australia), Jooyoung Eom of the Kyungpook National University (South Korea), Jianli Chen of the Hong Kong Polytechnic University (Hong Kong), and Clark R Wilson of the University of Texas at Austin (the US). The scientists have opined that the displacement of the Earth’s axis is very insignificant. Hence, it is not possible to understand the impact of this the displacement on human life right now. However, the extraction of huge amounts of groundwater is one of the causes of the rise in sea level. Ki-Weon Seo, the Lead Author of the latest study, has explained: “Mass change on the equator or pole cannot affect change in the rotational pole. Rotational pole change is actually associated with the moment of inertia of the Earth, which is sensitive to midlatitude mass change.”

As far as astronomy is concerned, the axial tilt, also known as obliquity, is the angle between a rotational axis of the Earth and its orbital axis. The Earth currently has an axial tilt of about 23.44 Degrees. This value remains the same relative to a stationary orbital plane throughout the cycles of axial precession. However, the ecliptic (Earth’s orbit) moves due to planetary perturbations, and the obliquity of the ecliptic is not a fixed quantity. At present, it is decreasing at a rate of about 46.8 inch per century. In fact, the Earth spins around this imaginary axis that passes through the North Pole, its centre of mass, and the South Pole, just like a top spins around its spindle. For years, scientists have known that the poles and the axis keep shifting naturally as the mass distribution in and on the planet changes. This phenomenon is commonly known as Polar Motion.

There are several other reasons behind the Polar Motion. One can mention ocean currents or hurricanes. One of the important reasons is human activity. For example, glaciers are melting due to Climate Change. As a result, the position of the axis changes with the change in the mass of the Earth’s water. A group of scientists explained this in 2016.

Lead Author Seo has stressed that they took observational data, spanning 17 years, and a computer model to find out which factors affected the Earth’s rotation of axis the most. “I calculated variations of the spin axis using many kinds of data, including atmospheric pressure, ocean bottom pressure, artificial reservoirs behind dams, polar ice, mountain glacier, wind, current and finally groundwater. The estimated spin axis variations did not agree with the observation when excluding the groundwater effect. After including it, estimation agreed really well with observation,” he added.

The water extracted from the ground for irrigation and meeting the world’s freshwater demands, eventually, goes into the oceans. Seo has confirmed that groundwater extraction is one of the major contributors to the global sea level rise. Their calculations matched with previous research, which estimated that groundwater extraction raised global sea levels by 6.24mm between 1993 and 2010.

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Published by Koushik Das

Koushik Das (born on May 16, 1976 in Kolkata) is a career journalist. Based in the Indian capital of New Delhi, Koushik writes mainly about foreign policies and current geopolitical issues, and rarely about other topics. His own political ideas are highly influenced by Antonio Gramsci, Louis Althusser, Michel Foucault, Michael Oakeshott and others. English philosopher and political theorist Oakeshott (Dec 11, 1901-Dec 19, 1990) says that “in political activity, men sail a boundless and bottomless sea. There is neither harbour for shelter nor floor for anchorage, neither starting-place, nor appointed destination. But we have to keep afloat”. (Rationalism in Politics, 1962) As a student of Political Science, Koushik loves to share his views on issues, which have great impacts on his thought process (and also on India, South Asia and of course on the global community), with his readers through his website – Boundless Ocean of Politics. By doing so, he tries to keep himself afloat. You will find some of his articles in https://inserbia.info/today/ (https://inserbia.info/today/author/kou_das13_i/), as he has been trying to assess the global geopolitics since 2003. You can also mail him at kousdas@gmail.com View all posts by Koushik Das