Study Finds Over-extraction of groundwater has shifted the Earth’s axis! What are its implications on Climate change?

By Aayushi Sharma

According to a recent study, the Earth’s axis of rotation has changed due to the overuse of groundwater for agriculture and drinking. The report notes that between 1993 and 2010, people removed almost 2,150 gigatons of groundwater, which caused the planet’s axis to migrate eastward at a rate of 4.36 cm per year. 

The study demonstrates that people extracted over-limit water from the ground that it has affected the planet’s axis and contributed to global sea level rise, even though the shift isn’t big enough to have real-life repercussions.

Groundwater and Climate change

Over one-third of the water utilized worldwide comes from underground sources. Groundwater is essential for preserving the global ecosystem and supporting human needs for drinking water and agricultural production in the mid-latitude arid and semiarid regions without sufficient surface water supply from rivers and reservoirs. With population increase, the need for groundwater is rising quickly, and climate change is stressing water supplies even more and increasing the likelihood of severe droughts. 

Groundwater systems are impacted by climate change in a number of ways. Climate change may have an impact on groundwater recharge by affecting the rates of deeper percolation and soil infiltration in the hydrological cycle. Additionally, as temperatures rise, there is less water available to replenish groundwater due to an increase in evaporative demand over land. In contrast, groundwater pumping and the indirect effects of irrigation, and changes in land use are the principal causes of anthropogenic influences on groundwater resources.

How does the Earth’s axis keep shifting?

Similar to how a top spins on its spindle, Earth revolves around an imaginary axis that runs through its north pole, center of mass, and south pole. Since ancient times, scientists have understood that the axis and poles of the globe naturally shift as the distribution of mass within and on it changes. The term “polar motion” refers to this phenomenon. One of the lead authors of the study, Ki-Weon Seo, said that the shift of Earth’s axis varies several times a year. 

For instance, as rocks circulate slowly inside Earth’s mantle, the mass of the planet shifts, changing where the rotating axis is located. 

Other factors, such as storms and ocean currents, can also contribute to polar motion. Human activities, however, also have an impact on this phenomenon. A group of scientists showed in 2016 that the melting of glaciers and ice in Greenland and other climate-driven changes in the distribution of water mass can cause the Earth’s axis to move. Five years later, an additional study found that since the 1990s, the rotating axis had been shifting more than typical due to climate change. For instance, as rocks circulate slowly inside Earth’s mantle, the mass of the planet shifts, changing where the rotating axis is located. 

What are the key findings of the new study?

The scientists used a computer model and observational data spanning 17 years to conduct the study and determine the factors that had the greatest impact on the Earth’s rotation of axis. At first, the team’s prognosis couldn’t be matched with the degree of movement that researchers had previously noted.

According to the study, groundwater extraction from North America and northwest India, both of which are at midlatitudes on Earth, had a greater influence on polar motion than extraction from poles or equator.

The freshwater that is extracted from the earth for irrigation and to meet global freshwater needs eventually finds its way into the oceans. 

A sea level dip across the Indian and Pacific seas next to regions of groundwater depletion is a result of SAL, which causes sea level to decline near areas of decreasing water mass on land. The majority of the world’s seas see an increase of about 10 mm. 

The figure here shows the Indian and Pacific Ocean areas with high depletion. 

Researchers confirmed that one of the main causes of the global sea level increase is groundwater exploitation. They found agreement between their findings and an earlier study that found extraction of groundwater increased global sea levels by 6.24 mm between 1993 and 2010.

 References: 

• https://indianexpress.com/article/explained/explained-climate/groundwater-extraction-shifted-earths-axis-study-8692912/ 
• https://www.downtoearth.org.in/news/world/groundwater-extraction-has-tilted-earth-s-spin-how-likely-is-it-to-fuel-climate-change–90073 
• https://www.researchgate.net/publication/371596241_Drift_of_Earth’s_Pole_Confirms_Groundwater_Depletion_as_a_Significant_Contributor_to_Global_Sea_Level_Rise_1993-2010
• https://www.nature.com/articles/nclimate1744
• https://www.nature.com/articles/s41467-020-17581-y
• https://www.watereducation.org/aquapedia/groundwater