Earth’s tilt has changed by 31 INCHES thanks to humans
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Our insatiable need for water may keep us alive, but it’s shifting the Earth’s tilt, a new study shows.
Researchers in Korea say removing groundwater around the world for drinking water and irrigation changes Earth’s mass and, in turn, makes its axis “wobble.”
According to the team, we’ve moved such a large mass of water that the Earth has tilted 31 inches (78.5 cm) eastward between 1993 and 2010 alone.
Changing the position of the axis could potentially increase the amount of sunlight the poles get, which could increase the melting of polar ice.
And in a vicious circle, melting ice and resulting sea-level rises could alter Earth’s mass distribution even further, previous research has shown.
Unlike geographic north and south, which remain in a fixed position, Earth’s pole of rotation varies relative to the Earth’s crust β a process called polar motion. Korean researchers compared the polar motion (red arrow, ‘OBS’) with the modeling results without (dotted blue arrow) and with (solid blue arrow) groundwater mass redistribution. The groundwater mass redistribution model agrees much more closely with the observed polar motion, telling the researchers the magnitude and direction of groundwater’s influence on the Earth’s rotation
The new study was led by researchers at Seoul National University and published in the journal Geophysical Survey Letters.
“Earth’s rotational pole actually changes a lot,” said Ki-Weon Seo, a geophysicist at Seoul National University.
‘Our research shows that among climate-related causes, groundwater redistribution has the greatest influence on the drift of the rotating pole.’
Earth’s pole of rotation is the point around which the planet revolves — and where the imaginary axis would protrude if it were a physical object, such as the axis on a spinning globe in a classroom.
Unlike geographic north and south, which remain in a fixed position, Earth’s pole of rotation varies relative to the crust β a process called polar motion.
But the distribution of water on the planet affects how mass is distributed, so when water is taken away from part of the planet, the axis starts to move and wobble.
It’s a bit like adding a little bit of weight to a spinning top, or applying even the slightest pressure to one side of a basketball as it spins perfectly around someone’s finger.
While the wobbling of the Earth’s axis does not affect our daily lives, it must be taken into account to get accurate results from GPS, satellites and ground observatories.
Humans extract groundwater (water held underground in the soil or in rock pores and crevices) to use for drinking and to irrigate crops. In the photo a borehole for the extraction of groundwater
Total change in groundwater storage on land (a) and associated sea level variation (b) for 1993β2010. Units are mm of water
It was in 2016 that researchers announced that the distribution of water on Earth could change the position of the planet’s axis.
At the time, the researchers said the melting of ice caps changed this distribution, but now it’s clear that humanity’s use of drinking water is also responsible.
Humans extract groundwater – water held underground in the soil or in rock pores and crevices – to use for drinking water and to irrigate crops.
For the study, the team relied on previous estimates of how much groundwater was being depleted, published by a group of Dutch experts in 2010.
This team found that humans pumped up 2,150 gigatons of groundwater between 1993 and 2010, equivalent to more than 6 millimeters of sea level rise.
The Korean team looked at the observed changes in the drift of Earth’s rotational pole and the movement of water – first considering only ice sheets and glaciers, then adding different scenarios of groundwater redistribution.
The model only matched the observed polar drift when the researchers counted 2,150 gigatons of groundwater redistribution.
Without it, the model would have removed 31 inches (78.5 cm) or 1.7 inches (4.3 cm) of drift per yearβproving that groundwater redistribution was responsible for this distance.
The location of the groundwater matters for how much it can alter polar drift, the team said.
Redistribution of water from mid-latitudes β the region between the Tropic of Cancer and the Tropic of Capricorn β has a greater impact on the rotating pole, they found.
The tropics are regions on Earth that lie between the latitudes of the Tropic of Cancer and the Tropic of Capricorn (marked in red)
As we know from school spinning globes, the Earth rotates on an axis. What is less known is that the position of this axis moves (file photo)
During the study period, most of the water was redistributed in western North America and northwestern India, both at mid-latitudes.
Attempts to slow groundwater depletion could theoretically reverse the change in polar drift, the team says, but only if such conservation approaches are sustained over decades.
However, movement of water is not the only factor that influences the position of the rotating pole, according to the team.
Sloshing molten iron in the Earth’s core, melting ice, ocean currents, and hurricanes are all other causes of the wandering poles.
“The way the planet wobbles is affected by our activities,” said Surendra Adhikari, a geophysicist at NASA’s Jet Propulsion Laboratory who was not involved in the study. Science.
It is already known that sea level rises can cause polar drift, but polar drift can in turn affect climate – potentially creating a kind of vicious circle.
For example, as the North Pole gets closer to the equator, the Earth’s axis of rotation will tilt more toward the Sun, which can make the Northern Hemisphere hotter.
At the moment, the rotational pole normally changes by a few meters within about a year, so changes due to groundwater pumping do not run the risk of seasonal shifts.
But on much larger “geologic” timescales, polar drift could potentially have such impacts on climate, Adhikari said.