A study published in Geophysical Research Letters reveals that excessive groundwater extraction has caused a significant shift in Earth’s rotational pole.
About Earth’s Axis
- Definition: Earth’s axis is an imaginary line running through the planet from the North Pole to the South Pole.
- It is the central line around which Earth rotates, completing one full spin approximately every 24 hours.
- The axis is tilted at an angle of 23.5 degrees relative to Earth’s orbital plane (the plane in which Earth revolves around the Sun).
- This tilt causes the yearly cycle of seasons.
- Changes in the Axis
- Earth’s axis is not fixed: It experiences gradual shifts due to changes in the planet’s mass distribution (e.g., melting ice caps, groundwater depletion).
- These movements, known as axial precession or polar motion, occur over time and can have long-term impacts on Earth’s stability and climate.
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Groundwater
- Groundwater is water stored in the cracks and spaces of rock, soil, and sand beneath the Earth’s surface.
- It is a key component of the hydrological cycle, replenished by rain and surface water infiltration.
- Groundwater is stored in natural underground reservoirs called aquifers.
- Challenges of Over Extraction of Groundwater:
- Depletion: Excessive extraction exceeds natural recharge rates, leading to declining water tables.
- Land Subsidence: Over-pumping can cause the ground to sink.
- Water Quality: Overuse can result in contamination, including salinity and pollution.
- Environmental Impact: Reduced groundwater can dry up lakes, rivers, and wetlands.
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Key Findings Of the Study (1993–2010)
- Pole Drift:
- The earth’s axis has tilted by 31.5 inches (nearly 80 centimetres eastward)
- Drift occurred at a rate of 4.36 centimeters per year due to groundwater depletion.
- Groundwater Extraction:
- Humans extracted an estimated 2,150 gigatons of groundwater during this period.
- This massive extraction contributed to a sea level rise of about 0.24 inches.
- Mechanism of Polar Motion: Polar motion, the movement of Earth’s rotational axis relative to its crust, is influenced by changes in mass distribution across the planet.
- The redistribution of groundwater from aquifers to oceans has emerged as a significant factor affecting this motion.
- Groundwater vs. Climate-Related Factors such as Ice Sheet Melting:
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- The study’s models show that groundwater depletion has a larger impact on polar drift than previously considered climate-related factors such as ice sheet melting.
Regional Impact and Implications
- Role of Groundwater Extraction: The study underscores the profound role of groundwater extraction in altering Earth’s geophysical properties, with significant consequences for planetary dynamics.
- Key Regions of Groundwater Extraction: The research identifies western North America and northwestern India as key regions where significant groundwater extraction has occurred.
- These mid-latitude regions have a substantial influence on polar drift due to their geographical location and high extraction volumes.
- Immediate Effects: The current shift in Earth’s tilt is not yet significant enough to alter weather patterns or seasons.
- Long-Term Risks: Continued groundwater depletion could have long-term climatic impacts over geological time scales.
- Changes in polar motion could eventually influence global climate systems.
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Way Forward
- Call for Sustainable Water Management: Findings emphasize the urgent need for sustainable groundwater management to mitigate further polar drift and its potential impacts.
- Interconnectedness of Human Activities and Planetary Dynamics: This study not only highlights the interconnectedness of human activities and planetary dynamics.
- It also stresses the importance of considering anthropogenic factors in understanding Earth’s physical processes.
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