Humans Have Pumped Enough Groundwater to Shift Earth’s Rotational Pole, Study Says
In a new study, geophysicists have determined that Earth’s rotational pole has shifted almost one meter in a 20-year period due to groundwater being pumped from one location and moved elsewhere.
Researchers found that pumping and moving groundwater led the Earth’s rotational axis to shift about 80 centimeters (31.5 inches) east from 1993 to 2010. The results were published in the journal Geophysical Research Letters.
In a previous study, researchers used climate models to estimate that about 2,150 gigatons of groundwater was pumped from 1993 to 2010. According to the study, this groundwater contributed to about 0.24 inches of sea level rise. But these estimates were difficult to prove.
Now, by analyzing the shift of the rotational axis in models and observed changes, researchers determined the shift couldn’t be explained without considering how much groundwater humans pumped during the timeframe.
“Earth’s rotational pole actually changes a lot,” Ki-Weon Seo, lead author of the study and a geophysicist at Seoul National University, said in a statement. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”
According to Yale Environment 360, the groundwater was pumped to farms and cities before flowing out toward the coasts, where it contributed to sea level rise.
Scientists first noticed how water could shift the planet’s polar motion in 2016, but research had not considered how groundwater pumping could contribute to this phenomenon. In the latest study, the geophysicists started by modeling observed changes to Earth’s rotational pole based on movements of ice sheets and glaciers. The model only accurately depicted observed changes when the team added 2,150 gigatons of groundwater redistribution to its considerations.
“I’m very glad to find the unexplained cause of the rotation pole drift,” Seo said. “On the other hand, as a resident of Earth and a father, I’m concerned and surprised to see that pumping groundwater is another source of sea-level rise.”
The rotational pole naturally shifts, but over time, with shifting caused by groundwater redistribution, the changes could impact climate, according to Surendra Adhikari, a research scientist at the Jet Propulsion Laboratory who was involved in the 2016 study.
Next, researchers may need to look at shifts in the rotational pole from the past to consider how these shifts could impact or be impacted by climate.
“Polar motion data are available from as early as the late 19th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years,” Seo explained. “Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer.”