The lengths of day and night are determined by the tilt of the Earth’s axis. If the axis was straight from top to bottom, pointed at a right angle to the Earth’s orbit around the sun, the intensity and distribution of the sunlight falling on Earth’s hemispheres would be the same throughout the year, and we would not have seasons. Ideally, Earth’s axial tilt (also known as obliquity of the ecliptic) is supposed to be 23.5 degrees. Also, the rotational speed of the Earth depends to some extent on the overall distribution of Earth’s mass.
A new study has found that unbridled groundwater extraction has resulted in Earth getting further tilted nearly 80 cm eastward. Scientists have found, humans have pumped out 2150 billion tonnes of groundwater over the years, causing sea-level rise which in turn misbalanced the water and mass distribution throughout the globe.
Unlike a globe, which has a fixed axis and spins stably, the Earth’s axis wobbles. It is somewhat like a whirligig gone out of balance, where the Earth’s rotational axis tends to wander in a circular motion various meters wide annually due to seasonal changes, the molten core, and also powerful cyclones
Scientists have been tracking these activities for a long time, and a study showed how the movement around the world gave rise to this wobble in the earth’s axis. The overall factors that contributed to this change in axial tilt are the following.
- Water redistribution from aquifers to the oceans: Groundwater pumped up from the aquifers and drained out into the ocean has been responsible for Earth getting further tilted by 80 centimetres (31.5 inches). The Geophysical Research Letters publicized that the sea level has risen to 6.24mm, due to which “Earth’s pole has drifted toward 64.16 degrees E at a speed of 4.36 centimetres per year during 1993-2010”. Surveys conducted show humans have pumped out nearly 2150 billion tonnes of groundwater over these years. The paper mentions, “We show that the model estimate of water redistribution from aquifers to the oceans would result in a drift of Earth’s rotational pole, about 78.48 cm toward 64.16 degrees E”. Ki-Weon Seo, the geophysicist who led this team of researchers said, “The redistribution of groundwater actually has the largest impact on the drift of the rotational pole”.
- Thawing of massive glaciers due to global warming: Glaciers all over the world are melting rapidly due to global warming. This adds to the sea level rising. A research concluded that ”The accelerated decline in water stored on land resulting from glacial ice melting is the driver of the rapid polar drift after the 1990s”
Will the drifting of Earth’s poles cause severe climate change? Well, increase in pollution, greenhouse gas emission, and deforestation have cumulatively caused a considerable amount of climate change already. This slight drift in rotational poles will not have a severe impact on climate change, but scientists have warned that over a longer time period it might affect climatic conditions.
India’s part to play in this phenomenon
The scientists conducting the research also pointed out that the location of the reduction matters because that determines how much the axis deviates. They estimated that most of the water redistribution happened in western North America and northwest India.
Groundwater decline has been a matter of concern all over India in the last few years. About 95% of it was traced in north India, in the states of Punjab, Haryana, Delhi, U.P, Rajasthan, and Gujarat. Even a few south Indian states of Karnataka, Tamil Nadu, Telangana, and Andhra Pradesh are suffering from this problem now.
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