Humans have changed the Earth's axis — and our GPS and satellite navigation systems need it to work

This has "very important practical implications" an author of a new study on groundwater explains to Salon

By Matthew Rozsa

Staff Writer

Published June 21, 2023 3:00PM (EDT)

Planet Earth On A Tightrope (Getty Images/mspoli)
Planet Earth On A Tightrope (Getty Images/mspoli)

As humans extract more and more groundwater, we are literally changing the composition of the planet, so much so that we are also shifting the tilt of the globe.

According to a recent study in the scientific journal Geophysical Research Letters, countless amounts of groundwater have been extracted from beneath our feet. Consequently, the True North Pole has shifted at a rate of 4.36 centimeters per year (or more than 1.7 inches). Between 1993 and 2010 alone, that amounted to more than 2 trillion tons of groundwater, which exists in saturated regions underground and can be used for drinking, irrigation, sanitation and manufacturing.

The North Pole is iconic for being the northernmost point on our planet — yet there is no single place that officially exists as a fixed "North Pole." Instead Earth's so-called "True North Pole" is whichever place that is northernmost on the planet, a fact determined by where the globe's axis of rotation meets its surface. (The True North Pole is distinct from — though close to — the northernmost magnetic pole, which is the point where Earth's magnetic field points vertically downward.) All of this may be a bit hard to follow but the important part is, if physical changes to the planet Earth alter its axis of rotation, the location of the True North Pole will alter accordingly.

This northern shift is far from the only way that humans have changed the planet by extracting groundwater. As this process ultimately redistributes water from aquifers to oceans, it has been speculated that it (along with man-made climate change) contributes to the ongoing problem of rising sea levels. The new study used relevant climate and groundwater data to create a model that showed how the total groundwater depletion between 1993 and 2010 was equivalent to 0.24 inches (6.24 mm) of global sea level rise. 

"The contribution of our study was to take these groundwater extraction data and compute the effect on the drift of the rotation axis (pole)."

"The contribution of our study was to take these groundwater extraction data and compute the effect on the drift of the rotation axis (pole)," study co-author Clark R. Wilson, a professor of geological sciences at the University of Texas at Austin, explained in an email with Salon. He argued that there are three main takeaways from their research.

"The volume of groundwater and geographical locations in the published estimates for the year 1993-2010" are reliable and shows that "the projected drift of the pole from their estimate agrees with the well-measured polar motion (including also estimates of other contributors)" on the subject, Wilson told Salon. He added that "given that the groundwater extraction volume and geographical distribution estimate is confirmed as good by point number 1, the associated contribution to sea level rise due to groundwater extraction is also confirmed."

The final conclusion is thus that "an important contributor to the drift of the pole (rotation axis) is now identified by this study," one that has "very important practical implications. Knowing via measurements from several space geodetic techniques (and also being able to predict in the future) the precise location of the rotation axis within Earth is essential to making the Global Positioning System and other satellite navigation systems work. This is because the rotation axis location is essential to convert the ranges to the GPS satellites into geographical locations on Earth."

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist.

"Measuring the location of the rotation axis very precisely is really important to the GPS system and so to everyone who uses it, either with a cell phone, flying in an aircraft, etc."

If this news is causing you to picture a world where cars start directing owners off of cliffs and cell phones become completely useless, don't worry. The effects will be more subtle — but no less real.

"Most are not aware that the rotation axis wobbles and has drifted from North Geographic pole in the last 123 years by 10-15 meters," Wilson told Salon. "So the influence of this motion on human time scales is not observable to most and has no significant effect on processes on or within Earth. But measuring the location of the rotation axis very precisely is really important to the GPS system and so to everyone who uses it, either with a cell phone, flying in an aircraft, etc."

Wilson added, "The military is quite interested in predicting future positions of the pole as this affects their use of GPS in weapons." He also noted that the study's findings have serious implications for regions that are water-starved but rely on groundwater for things like irrigation.

Looking at "the geography of water extraction," Wilson highlighted the "Middle East, Northern India and China, and [the] Western US" as areas that are at risk of suffering "future limitations on irrigation." In a similar vein, "the mid-latitude locations of these regions of depletion is very efficient at causing the pole to drift (the most efficient latitude for causing polar drift is 45 degrees north or south)" as a result of all the groundwater being taken out of the Earth there.

Lorenzo Rosa, a principal investigator at Carnegie Institution for Science and a scientist who was not involved in the study, told Salon that if irrigation becomes more difficult in water-starved regions due to limited groundwater access, "the alternatives to groundwater are desalination or water transfers to increase supply." At the same time, Rosa pointed out that "it is also important to reduce demand by increasing efficiency by planting less water intensive crops." The consequences of failing to do so are dire indeed: "If we run out of water we will need costly solutions to overcome water scarcity," Rosa concluded.

By Matthew Rozsa

Matthew Rozsa is a staff writer at Salon. He received a Master's Degree in History from Rutgers-Newark in 2012 and was awarded a science journalism fellowship from the Metcalf Institute in 2022.

MORE FROM Matthew Rozsa