Groundwater extraction has tilted Earth’s spin; how likely is it to fuel climate change?

Subject: Geography

Section: Physical geography

Context:

Humans have caused marked tilts in the Earth’s axis by pumping water out of the ground and moving it elsewhere, according to a new study.

Study findings:

A 2021 study found that the direction of polar drift moved from southward to eastward in 1995 and that the average drift speed from 1995-2020 was 17 times quicker than from 1981-1995.
Pronounced shifts in the Earth’s axis of rotation can impact our planet’s climate.
Groundwater pumping has tilted the planet nearly 80 centimetres east between 1993 and 2010 alone.
- The water circulated across the planet determines how mass is distributed.
- Scientists had predicted that between 1993 and 2010, people pumped 2,150 gigatons of groundwater, or more than 6 millimetres (0.24 inches), of sea level increase.
- However, it is difficult to validate that estimate.

Shift of Earth’s axis:

In the past, the poles’ drift was only caused by natural forces like ocean currents and the convection of heated rock deep beneath the Earth.
But the new research pitched the redistribution of groundwater as the primary culprit for the drift.
Water’s role in altering the Earth’s rotation was discovered in 2016, and until now, the contribution of groundwater to drifts has been unexplored.
The planet’s geographic north and south poles are where its axis intersects the surface; however, they are not fixed.
- The axis and hence the poles fluctuate due to variations in the Earth’s mass distribution.
Risk involves:
- The rotational pole normally changes by several metres within about a year, so changes due to groundwater pumping don’t run the risk of shifting seasons.
- But on geologic time scales, polar drift can have an impact on climate.
- Redistributing water from the mid-latitudes significantly influences polar drift; therefore, the location of redistribution determines polar drift.
- During the study period, most redistribution occurred in western North America and northwestern India — both located at mid-latitudes.

Earth’s Axis of Rotation:

It is the line along which it spins around itself as it revolves around the Sun.
Earth’s axial tilt (also known as the obliquity of the ecliptic) is about 23.5 degrees. Due to this axial tilt, the sun shines on different latitudes at different angles throughout the year. This causes the seasons.
The points on which the axis intersects the planet’s surface are the geographical north and south poles.
The location of the poles is not fixed. The axis moves due to changes in how the Earth’s mass is distributed around the planet. Thus, the poles move when the axis moves, and the movement is called “polar motion”.
Generally, polar motion is caused by changes in the hydrosphere, atmosphere, oceans, or solid Earth. But now, climate change is adding to the degree with which the poles wander.
According to NASA, data from the 20th century shows that the spin axis drifted about 10 centimetres per year. Meaning over a century, polar motion exceeds 10 metres.