2023-06-19 15:30:05
Humans have extracted such a large mass of water that the Earth’s axis of rotation has tilted almost 80 centimeters to the east in the period between 1993 and 2010. It is the main conclusion of a new research published in the magazine Geophysical Research Letters.
The scientists based their calculations on previous studies where it was estimated that humans had pumped 2,150 gigatons of groundwater between 1993 and 2010which is equivalent to a sea level rise of more than 6 millimeters.
One of the premises of the researchers has to do with the rotation pole, that is, the point around which the Earth rotates. The planet moves during a process called polar motion, which is when the position of the Earth’s pole of rotation varies with respect to the Earth’s crust. Like adding a bit of weight to a spinning top, the Earth spins slightly differently as the water moves along, the experts explain.
“The pole of rotation of the Earth changes a lot”, indicates Ki-Weon Seo, a geophysicist at the University of Seoul who is leading the study. “Our research shows that, among climate-related causes, groundwater redistribution is the one that most influences the deviation of the pole of rotation”.
This is the first time that the influence of groundwater on rotational changes has been examined.
The ability of water to change the Earth’s rotation was discovered in 2016, and until now, the influence exerted by the water present under the Earth’s surface on these had not been contemplated. rotational changes.
During the study, the researchers modeled the observed changes in the tilt of the Earth’s pole of rotation, and thus the movement of water: first, considering only ice sheets and glaciers, then taking into account different groundwater redistribution scenarios.
That is, they compared the observed polar motion with the model results with and without groundwater mass redistribution. The model only matched the observed polar variation by including 2150 gigatons redistribution of groundwater. Without it, the model was deviating 78.5 centimeters, or 4.3 centimeters per year.
Seo acknowledged having found an answer to “the inexplicable cause of the deviation of the pole of rotation”, but, on the other hand, he was surprised to discover that the extraction groundwater may be “another cause of sea level rise.”
Researchers compare the observed polar motion (red arrow, “OBS”) with model results without groundwater mass redistribution (dashed blue arrow) and with groundwater mass redistribution (solid blue arrow). Geophysical Research Letters
It should be noted that the position of groundwater is important due to the fact that it could change the polar rotation; and indeed, the redistribution of water from the latitudes medias has a greater impact on the pole of rotation.
During the period studied, the largest amount of water was redistributed in the western North America and northwestern Indiaboth in mid-latitudes, according to a note released by the American Geophysical Union.
Consequence on the climate
Attempts by countries to slow down rates of groundwater depletion, especially in sensitive regions, could theoretically alter the tilt change, but only if such approaches are sustained over decades, the study author argues.
Normally, the pole of rotation varies several meters in a year, so changes due to groundwater pumping do not risk upsetting the seasons. However, on a geological time scale, this deviation can impact on the climateaccording to scientists.
On a geological time scale, the deviation of the rotation pole can affect the climate, as pointed out by experts
“Observing changes in the Earth’s pole of rotation is useful for understanding variations in the water storage on a continental scale”, explains Seo.
Given that data on polar movement has been available since the end of the 19th century, the expert affirms that this information can be used to “understand the variations in continental water storage during the last 100 years.”
He also notes a final reflection: “Were there changes in the hydrological regime as a consequence of global warming? Polar motion could hold the answer.”
Reference:
Ki-Weon Seo et al. “Drift of Earth’s Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010”. Geophysical Research Letters (2023)
Fuente: American Geophysical Union
Rights: Creative Commons.
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