Environment & Biodiversity

Groundwater extraction causes the Earth’s tilt axis to shift

  • According to a recent study undertaken by scientists at Seoul National University, groundwater extraction has caused a change in the planet’s axis, leaning it approximately 80 cm to the east.
  • This phenomenon, together with melting ice caps and glaciers, has implications for the earth’s rotation, sea-level rise, and water resource allocation.

Axis and Rotation of the Earth

  • The axis and rotation of the Earth play important roles in defining our planet’s climate, seasons, and day-night cycles.
  • Here are some important facts about the Earth’s axis and rotation:
  • Axis: The axis is an imaginary line that stretches between the North and South Poles and is slanted at an angle of approximately 23.5 degrees relative to the orbital plane of the planet around the Sun. This tilt is responsible for the seasons on Earth.
  • Earth rotates on its axis from west to east, completing one full rotation every 24 hours. This rotation is responsible for the day-night cycle. Daylight falls on the side of the Earth facing the Sun, while darkness falls on the opposite side, resulting in day and night.
  • Polar Regions: The Earth’s axis is tilted relative to its orbital plane. Because of this inclination, the Polar Regions undergo seasonal fluctuations in daylight. The North Pole is tilted towards the Sun at the summer solstice (around June 21), resulting in 24 hours of continuous daylight in the Arctic Circle and 24 hours of darkness in the Antarctic Circle. During the winter solstice (about December 21), the opposite occurs.
  • The equator is an imaginary line that runs equidistant from the poles and divides the Earth into the Northern and Southern Hemispheres. Throughout the year, the equator has very regular day and night lengths, with two equinoxes happening when the Sun is directly above the equator. Day and night are roughly equal in length around the equinoxes (around March 21 and September 21).
  • Precession (Cyclic Wobble): In addition to its axial tilt, Earth suffers precession, which is a gradual, cyclic wobble. Over a period of around 26,000 years, this wobble causes the orientation of the Earth’s axis to fluctuate gradually. Precession has no effect on the tilt or length of the seasons, but it does modify the positions of the celestial poles as well as the timing of Earth’s closest approach to the Sun (perihelion) and farthest point (aphelion).

Why is this in the news?

  • Unlike a stable rotating globe, the earth’s axis wobbles due to a variety of variables including weather, seasonal fluctuations, the molten core, and natural disasters such as hurricanes.
  • Scientists have been tracking this motion in relation to celestial occurrences, but the role of water movement, especially groundwater extraction, has been overlooked until now.
  • Every year, the earth’s axis wobbles in a circular pattern several metres broad.

The Study’s Findings

  • Researchers at Seoul National University developed a climate model that links the earth’s axis shift to water transport, including ice cap and glacier melting.
  • The model initially did not match the observed axis drift until groundwater extraction was introduced to the equation.
  • Groundwater pumping accounted for the rotation pole drift’s inexplicable cause.
  • Groundwater extraction caused an approximately 80-centimeter tilt to the east in the earth’s axis.

Consequences of Sea-Level Rise

  • The study found that between 1993 and 2010, about 2,150 billion tonnes of groundwater were pumped and drained into the oceans, contributing to a 6.24 mm rise in sea level.
  • Groundwater depletion influences the location and amount of the axis drift.
  • The most significant groundwater redistribution effects were observed in mid-latitude locations, including northwest India and western North America.

The Effect on Water Resources

  • Groundwater extraction for human purposes, such as irrigation, has an impact on the distribution and availability of water resources.
  • Excessive groundwater pumping has resulted in massive water redistribution, affecting the balance of surface water and groundwater supplies.
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