According to a new study published in Geophysical Research Letters, humans moved so much water by pumping water from Earth and transporting it elsewhere that Earth tilted eastward by about 80 centimeters (31.5 inches) between 1993 and 2010 alone.
Scientists previously estimated, based on climate models, that humans pumped 2,150 gigatons of groundwater between 1993 and 2010, equivalent to more than 6 millimeters (0.24 in) sea level rise. However, this assessment is difficult to verify.
One approximation is the Earth’s spin pole, which is the point around which the planet revolves. It moves when the position of the Earth’s spin pole changes relative to the Earth’s crust, during a process called polar motion. The distribution of water on the planet affects the mass distribution. The Earth spins a little differently when the water moves, like adding a little weight to the spindle.
“Earth’s spin pole actually changes a lot,” said Ki-Weon So, a geophysicist at Seoul National University who led the study. “Our study shows that, among climate-related causes, groundwater redistribution is indeed the largest contributor to the polar drift.”
The ability of water to alter the Earth’s rotation was discovered in 2016, and until now the specific contribution of groundwater to these rotation changes has not been investigated. In the new study, the researchers modeled the observed changes in Earth’s shift towards the poles and water movement – first they considered only ice sheets and glaciers, then added different groundwater redistribution scenarios.
The model barely matched the pole shift observed after the researchers included 2,150 gigatons of groundwater redistribution. Without it, the model shift was 78.5 centimeters (31 inches) or 4.3 centimeters (1.7 inches) per year.
“I am very happy to have found the unexplained cause of the renegade pole slip,” So said. “On the other hand, as an Earthling and parent, it worries and surprises me that the pumping of groundwater is another source of sea level rise.”
“This is a good contribution and certainly an important piece of documentation,” said Surendra Adhikari, a research scientist at the Jet Propulsion Laboratory who was not involved in the study. Adhikari published an article in 2016 on the redistribution of water affecting rotational shear. “They measured the role of groundwater pumping in mast movement, and that’s pretty important.”
The location of groundwater is important to the extent that it can alter pole drift; The redistribution of water from the mid-latitudes has a greater effect on the polar return. During the study period, most of the water was redistributed in western North America and northwestern India, both in mid-latitudes.
Attempts by countries to slow the rate of groundwater depletion, particularly in such sensitive areas, could theoretically reverse the slide, but only if such conservation approaches are sustained over decades, Seo said.
The pole of rotation typically shifts by a few meters during a year, so changes caused by groundwater pumping do not cause the seasons to shift. However, Adhikari said that on geological time scales, pole shift could have an impact on climate.
“Observing changes in Earth’s spin pole is useful for understanding continental-scale fluctuations in water storage,” Seo said. Said. “Data on the movement of the poles have been available since the end of the 19th century. So we can potentially use this data to understand fluctuations in water resources on the continent over the past 100 years. Has there been any change in the hydrological regime as a result of climate warming? The movement of the poles may hold the answer.” Source
Source: Port Altele
