Know More About Water Loss and Polar Drift
Using data on glacier loss and estimations of ground water pumping, Liu and her colleagues calculated how the water stored on land changed. They found that the contributions of water loss from the polar regions is the main driver of polar drift, with contributions from water loss in nonpolar regions. Together, all this water loss explained the eastward change in polar drift.
“I think it brings an interesting piece of evidence to this question,” said Humphrey. “It tells you how strong this mass change is—it’s so big that it can change the axis of the Earth.”
Humphrey said the change to the Earth’s axis isn’t large enough that it would affect daily life. It could change the length of day we experience, but only by milliseconds.
The faster ice melting couldn’t entirely explain the shift, Deng said. While they didn’t analyze this specifically, she speculated that the slight gap might be due to activities involving land water storage in non-polar regions, such as unsustainable groundwater pumping for agriculture.
Humphrey said this evidence reveals how much direct human activity can have an impact on changes to the mass of water on land. Their analysis revealed large changes in water mass in areas like California, northern Texas, the region around Beijing and northern India, for example—all areas that have been pumping large amounts of groundwater for agricultural use.
“The ground water contribution is also an important one,” Humphrey said. “Here you have a local water management problem that is picked up by this type of analysis.”
Liu said the research has larger implications for our understanding of land water storage earlier in the 20th century. Researchers have 176 years of data on polar drift. By using some of the methods highlighted by her and her colleagues, it could be possible to use those changes in direction and speed to estimate how much land water was lost in past years.