The recent publication of a study in the Geophysical Research Letters revealed the substantial influence of Groundwater Extraction on Earth’s rotational axis, in addition to its contribution towards increasing global sea levels. An analysis was carried out on alterations in Earth’s rotational pole drift and water movement by considering only ice sheets and glaciers first, then followed by incorporating various groundwater redistribution scenarios.
Contributing Factors to Earth’s Rotation
Polar motion, which is the movement of Earth’s rotational axis relative to its crust, is largely influenced by a range of factors such as weather patterns, seasonal changes, the molten core, and powerful hurricanes. This motion reflects the impact of material exchange and mass redistribution within each layer of Earth on the rotational axis. Typically, such movement results from changes occurring in the hydrosphere, atmosphere, oceans, or solid Earth.
Earth’s Geographic North and South poles are not fixed. They are points where Earth’s rotational axis intersects the surface, which fluctuates due to variations in the distribution of Earth’s mass. Traditionally, natural forces like ocean currents and deep beneath the Earth heated rock convection were the primary causes of poles’ drift. However, the latest research identifies groundwater redistribution as the main offender.
Discovery of Water’s Role in Earth’s Axis Alteration
The influence of water in modifying the Earth’s rotation was discovered only five years ago in 2016. Until that time, the contribution made by groundwater towards drifts remained uninvestigated.
Key Insights from the Research
Among the key findings, it was observed that groundwater pumping alone had tilted the Earth approximately 80cm east between 1993 and 2010. The distribution of mass across the planet is set by the circulation of water. In the aforementioned period, about 2,150 gigatons of groundwater were pumped, leading to over 6mm sea level rise.
Impact on Polar Drift
Over excessive groundwater pumping has resulted in the Earth’s pole to drift at a rate of 4.36 centimeters per year within 1993 and 2010, marking it as the climate-related element bearing the highest impact on polar motion. Most redistribution took place in western North America and northwestern India — both located at mid-latitudes — during the study period.
Groundwater Pumping Effect on Sea-Level Rise
The research also threw light on how groundwater pumping contributed to a sea-level rise of 6.24 mm during the same duration. Pumping from mid-latitude regions like northwest India and western North America exhibited the most significant influence on Earth’s axis drift.
Repercussions of Polar Drift
The rotational pole usually alters by several metres within approximately a year, so changes brought about through groundwater pumping don’t pose a risk of shifting seasons. Nonetheless, polar drift can have an impact on climate over geological time scales.
Recommendations for Addressing the Situation
The study recommends making efforts to slow down groundwater depletion rates, particularly in sensitive regions, which can theoretically alter the change in drift, but only if such conservation approaches are sustained for decades.
The Importance of the Study
The findings underline the need to tackle groundwater depletion and its worldwide repercussions. This discovery highlights the necessity of including groundwater depletion as a critical factor when analyzing Earth’s rotational dynamics and rising sea levels.
