Glacial melting due to global warming has probably been altering Earth’s poles since at least the 1990s, according to a new study published in Geophysical Research Letters.
Earth’s spin on its axis is determined, in part, by the distribution of weight around the globe, in the same way the spin of a top is determined by its shape. Satellite data from 2002 and later had already shown that climate change is altering this weight distribution, largely because melting glaciers and ice sheets have caused the North and South poles to drift.
As the planet warms, ice from glaciers and ice sheets migrates from land into the sea (as water), which majorly redistributes weight on the globe. This phenomenon, which scientists recently found more evidence for, ultimately shifts the planet’s axis, something scientists call ‘polar drift’.
“The Earth is like a spinning top, and if you put more mass on one side or the other, the axis of rotation is going to shift slightly,” explained Isabella Velicogna, a professor of earth system sciences at the University of California, Irvine, and a researcher at NASA’s Jet Propulsion Laboratory.
Notably, half the world’s glacial loss is coming from the United States and Canada, the study found.
Scientists had also observed polar drift in the 1990s, but uncovering the cause of that drift was tricky, because there were no direct satellite observations of water distribution around the globe from that era. Now, researchers have compared possible scenarios of total water distribution around the world and found that the best explanation for the changes to the poles in the 1990s is human-caused climate change. Melting ice sheets, combined with groundwater pumping for agriculture, altered the water distribution on the planet enough to make the planet’s axis shift.
Overall, the changes in polar drift aren’t noticeable in daily life. They might alter the length of the day by a millisecond or so over time, Vincent Humphrey, a climate scientist at the University of Zurich who was not involved in this research, said in a statement.
