The relative position of the polar axis to the Earth’s crust can be influenced by the distribution of water on the planet. Seo Ki-Weon, a geophysicist at Seoul National University in South Korea and the lead researcher, said, “The Earth’s polar shift has indeed changed significantly.”
According to Seo Ki-Weon, among the factors related to climate change, the redistribution of groundwater has the greatest impact on the shifting of the Earth’s polar axis.
Researchers have found that the Earth’s polar shift has shifted approximately 78.7cm eastward from 1993 to 2010 due to groundwater depletion. Illustration: ISTOCK
It was discovered in 2016 that water has the potential to alter the Earth’s rotation. However, the specific influence of groundwater on this change has not been clarified to date. In the latest study, researchers developed models to observe the movements of the polar shift and water. Initially, the models only considered ice sheets and glaciers. Later, the research team explored various possibilities related to the redistribution of groundwater.
The results showed that the model matched the polar shift observed between 1993 and 2010 when considering the redistribution of 2,150 billion metric tons of groundwater. Excluding the water extracted by humans from beneath the Earth’s surface, the model indicated a polar shift of approximately 78.7cm, equivalent to 4.3cm per year.
“I am delighted to uncover the mysterious cause of the polar shift. On the other hand, as an inhabitant of Earth and a father, I feel concerned and surprised to realize that groundwater extraction is one of the causes contributing to rising sea levels,” said Seo Ki-Weon, the geophysicist.
The figure of 2,150 billion metric tons of water, equivalent to nearly 0.6cm of global sea-level rise, stems from previous estimates by scientists regarding groundwater pumping from 1993 to 2010 over a 17-year period.
During that time, there was no direct observational evidence to support the previous estimate. The model in the latest study, which considered the redistribution of groundwater from various sources to the oceans, provided independent confirmation of that estimate.
Although not involved in the aforementioned study, Surendra Adhikari, a scientist at the Jet Propulsion Laboratory, California Institute of Technology, commented, “This is a significant contribution and certainly important work. They have quantified the impact of groundwater pumping on polar shift.”
Groundwater depletion, resulting from excessive pumping of water from sources such as underground aquifers, occurs at a faster rate than the replenishment of water. This groundwater is used for agricultural purposes and supplies urban areas.
After extraction, groundwater can find its way into the oceans through surface runoff or the processes of evaporation and precipitation.