Increased glacial melting coincided with a shift in pole movement in the mid-1990s.
According to a new analysis, the abrupt zag in the direction the North Pole was drifting in the 1990s was triggered in large part by glacial melt caused by climate change.
The geographic poles of Earth, where the planet’s axis pierces the surface, are not fixed. Instead, they follow seasonal and near-annual cycles, which are primarily influenced by weather patterns and ocean currents.
The poles drift over time as the planet’s weight distribution changes and alters its rotation around its axis, in addition to shifting around in relatively tight swirls just a few meters long.
The North Pole had been drifting toward the western edge of Canada’s Ellesmere Island since the mid-1990s. The pole then veered eastward by about 71 degrees toward Greenland’s northeastern tip. It has continued to move in that direction, at a rate of about 10 centimeters per year. Suxia Liu, a hydrologist at Beijing’s Institute of Geographic Sciences and Natural Resources Research, says scientists aren’t sure why this change occurred.
Liu and colleagues compared polar drift patterns to data from previous research on glacial melt around the world. Glacier melt in Alaska, Greenland, and the southern Andes, in particular, intensified in the 1990s. The team notes in the April 16 issue of Geophysical Research Letters that the timing of the melting, as well as the impact it would have had on Earth’s mass distribution, indicates that glacial melt caused by climate change helped cause the change in polar drift.
Although glacier melting can account for some of the shift in polar drift, it does not explain all of it, according to the team’s findings. So there must be other variables at work. Groundwater pumped from aquifers in one area, for example, will end up in an ocean far away due to extensive irrigation (SN: 10/9/19). Water management, including glacial melt, cannot justify the North Pole’s tack, but it can nudge the Earth’s axis significantly, according to the team.
The findings “reveal how much human activity can have an impact on changes to the mass of water stored on land,” says Vincent Humphrey, a climate scientist at the University of Zurich not involved in this study. And they show how large these mass shifts can be, he says. “They’re so big that they can change the axis of the Earth.”