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According to climate model estimations, groundwater levels have declined significantly during the twentieth century. This is in line with analysis of global average sea level budgets. According to some, the main anthropogenic cause of sea-level rise is groundwater depletion due to irrigation.
Climate models had previously been used by scientists to calculate that, between 1993 and 2010 the human race pumped more than 6, millimeters (0.24 inch) of water into the ground, or 2,150 gigatons. Although it’s difficult to confirm that estimate.
According to a new study, humans have moved so much groundwater that Earth’s axis has tilted east by approximately 80 cm (31.5 in) between 1993 and 2010.
The Earth’s rotational axis changes quite a bit. The study shows that the most important climate-related cause is the redistribution in groundwater.
The role that groundwater plays in the rotational shifts of the Earth was first discovered by scientists in 2016. However, this hasn’t been thoroughly studied. Scientists used computer simulations in this study to model the changes reported for the rotation of Earth’s pole, and water movement. They first considered ice sheets, glaciers, and other polar features, and later included several scenarios that altered groundwater distribution.
Researchers compare observed polar movement (red arrow “OBS”) with modeling results (dashed black arrows) without and (solid blue) with groundwater mass distribution. Researchers found that the model with redistributed groundwater masses was a better fit for observed polar movement. It also revealed the direction and magnitude of the groundwater influence on Earth’s rotation. Credit: Seo et al. Geophysical Research Letters (2023),
The model did not match observed pole movement until the researchers added 2150 gigatons groundwater redistribution. The model would have been off 78.5 cm or 31 inches without it. That is 4.3 cm (1.75 inches) per year.
Ki-Weon Seo is a geophysicist from Seoul National University, who conducted the study. I’m glad that the cause for the unresolved rotation pole shift has been found. As a parent and as a citizen of Earth, I am concerned to learn that groundwater pumping is also a source of rising sea levels.
Surendra Adhikari is a Jet Propulsion Laboratory research scientist. This is an important document and a great contribution. The role played by groundwater pumps on the polar movement has been quantified, and is pretty important.
The amount of groundwater that could affect polar drift is dependent on its location. Water redistributing in the midlatitudes will have a larger impact on rotational pole. Over the entire research period, the two midlatitude areas of northwest India and western North America had the most water redistribution.
Theoretically efforts made by nations to reduce groundwater depletion, especially in vulnerable areas, may affect drift. However, this is only true if these conservation measures continue for many decades.
Adhikari says The rotational pole changes about several meters in a year. Therefore, changes caused by groundwater pumping do not have the potential to shift seasons. On geologic timescales, however, the polar shift can have an impact on climate.
Seo says “Observing the changes to Earth’s rotational polar is helpful for understanding variations in continent-scale storage of water.” Polar motion data is available as far back as the 19th century. We can use these data to better understand the changes in continental water storage over the past 100 years. Did the climate warming cause any changes in hydrological systems? Polar motion may hold the key.”
Journal Reference
- Ki-Weon Seo, Dongryeal Ryu, et al. The Drift of Earth’s Pole confirms that groundwater depletion is a significant contributor to global sea level rise 1993-2010. Geophysical Research Letters. DOI: 10.1029/2023GL103509
