Groundwater deep inside the Earth is readily available but is hard to access compared to water reservoirs like rivers, lakes, and the oceans that we see today.
This underground water passes through the solid part of the planet, including those from rainfall or the mentioned bodies of water on the surface.
Fractures of rock formations and spaces between soil pores are gateways for groundwater.
Now, underground water reservoir depletion events have caused the Earth's axis to tilt.
One of the pieces of evidence is findings about the North Pole to have been drifting several centimeters per year.
This is according to a new study led by scientists from South Korea earlier this month, wherein they blame the "human-induced depletion" through excessive groundwater pumping amid an increasing population and demand for more water worldwide.
The full implications of the planet's tilting are not clear yet.
However, we know that the position and angle of Earth in the solar system relative to the Sun and the Moon also affect the weather, climate, and even some natural processes.
Moreover, the new research acknowledges that uneven global water distribution can affect Earth's axis even on a small scale.
What is Groundwater?
According to The Groundwater Foundation, groundwater is the water located underground, primarily in the cracks and gaps in soil, sand, and rock.
It is stored in aquifers, geologic formations where this underground water is stored and moves slowly.
In the United States, groundwater pumped to be used for drinking water by over 50% of Americans nationwide, including those living in rural areas.
Most use of groundwater is to irrigate crops, according to the foundation.
Also Read: Arizona's Groundwater Crisis: How Drought Is Impacting the State's Water Supply
Underground Water Reservoir Depletion
In the study published in the journal Geophysical Research Letters on Thursday, June 15, researchers from Seoul National University and other educational institutions used a climate model to reveal significant groundwater depletion from the said period.
In particular, the period between 1993 and 2010 indicated groundwater depletion and eventual sea level rise caused Earth's pole to drift toward 64.16 degrees east at a speed of 4.36 centimeters per year.
The data showed that not only climate change-triggered melting glaciers and ice caps cause global sea level rise but also groundwater depletion from irrigation activities like groundwater pumping.
Earth's Axis Tilts
The study places emphasis that the shifting water distribution triggered by melting on the Earth's surface amid global sea level rise is well-known and can affect the tilt of the planet's axis.
However, there is a lack of understanding, specifically from scientific literature and other studies, that groundwater depletion can also contribute to this phenomenon, the researchers said.
These findings came after results from the study showed the net water lost from underground water reservoirs between 1993 and 2010 was approximately over 2 trillion tons.
Based on the team's calculations and long-term data, as cited by the website Nature.
Related Article: Climate Change Causes the Earth's Axis to Shift