Pumping too much groundwater has changed Earth's spin

A recent study published in the journal Geophysical Research Letters reveals that human activities, specifically the pumping and relocation of significant amounts of groundwater, have had a substantial effect on the Earth's tilt. Between 1993 and 2010, the Earth shifted about 80 centimeters (31.5 inches) to the east due to these groundwater-related factors.

The research investigates into the influence of groundwater redistribution at the Earth's pole of rotation, which denotes the point around which the planet revolves. Disturbances in the distribution of water on Earth affect its mass distribution, which subsequently leads to changes in the position of the pole of rotation. This phenomenon, called polar motion, can be compared to changing the weight distribution on a top, causing it to spin differently.

The study's lead author, Ki-Weon Seo, a geophysicist at Seoul National University, emphasizes the substantial variability of Earth's pole of rotation.

According to the findings, groundwater redistribution has the most significant impact on spin pole drift compared to other climate-related factors.

Influence of water on Earth's rotation

Building on earlier research in 2016 that identified the influence of water on Earth's rotation, the scientists used models to simulate observed changes in Earth's rotational pole drift and water movement. Initially, the models only considered ice sheets and glaciers, but various groundwater redistribution scenarios were later incorporated.

The study determined that including 2,150 gigatons of groundwater redistribution in the model aligned the results with observed polar drift. Without accounting for groundwater, the model drifted 78.5 centimeters (31 inches), equivalent to an annual drift of 4.3 centimeters (1.7 inches). The research establishes that groundwater pumping is the main contributing factor to the observed drift of Earth's pole of rotation among climate-related causes.

The location of groundwater redistribution plays an important role in determining its effect on polar drift, with midlatitude redistribution exerting a greater influence on pole rotation. Western North America and northwestern India experienced the largest volume of water redistribution during the study period, both located in mid-latitudes. While changes caused by groundwater pumping do not pose an immediate risk of disrupting the seasons, on geologic time scales, polar drift can affect weather patterns.

Consequences of excessive Groundwater pumping

• Land subsidence: Pumping groundwater reduces the support it provides to the soil, leading to land subsidence. This process can damage infrastructure, such as roads and pipelines, and increase the risk of flooding.

• Saltwater Intrusion: Excessive pumping of groundwater in coastal areas can cause saltwater intrusion, contaminating freshwater aquifers and reducing agricultural productivity.

• Groundwater table depletion: Over-extraction leads to groundwater table depletion, resulting in water shortages, agricultural crises, and impacts on domestic water supplies.

• Ecological consequences: The reduction of groundwater affects the flow levels of rivers, lakes and wetlands, damaging ecosystems and impacting the wildlife that depends on them.

• Decreased water quality – Over-pumping disrupts natural filtration, leading to lower water quality.

• Socioeconomic impact: Adverse effects on agriculture can lead to increased food prices and food insecurity. Accessing water from deeper wells or distant sources increases costs.

• Higher energy costs: Extracting groundwater from greater depths requires more energy, which contributes to higher energy consumption and associated environmental and economic costs.

• Climate Change Impacts: Groundwater depletion contributes to sea level rise as the pumped water eventually reaches the sea, increasing its volume.

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