The Earth wobbles in various ways. Its axis of rotation not only changes direction with respect to the stars; it also moves with respect to the Earth’s own crust. This polar movement consists of several components. One of them is a displacement, a few centimeters a year, of the North Pole, which had been pointing towards 70° West. Humans have also left their mark on this planetary phenomenon, secular polar drift (not to be confused with magnetic pole drift). Climate change would be the reason why this movement has turned, since the mid-1990s, towards the east. Explained by Shanshan Deng of the Chinese Academy of Sciences and his collaborators in Geophysical Research Letters. This group has studied polar drift with a model. The model suggests that glacial melting , especially in Greenland, is the biggest contributor to this.

The exact position of the Earth’s axis depends on the distribution of the moving solid, liquid and gaseous masses of the planet. The irregular shape of this and different geophysical phenomena impart a complex movement to the axis. Some of its components are periodic (for example, the so-called Chandler wobble has a period of one and a half years). The winds, sea currents, changes in atmospheric pressure and the bottom of the oceans are involved in them above all, as Deng and his collaborators write. In addition, there is a non-periodic component, the slow polar drift. The long-term causes of this component are some movements of large solid land masses: the currents in the Earth’s mantle andthe slow uplift of the land following the retreat of the continental ice sheets .

But these factors are not changing fast enough to explain the recent change in drift direction. Researchers have long suspected that the missing factor is the melting of land ice masses.. Deng and his collaborators have separated the contributions of land, ocean and atmospheric elevation in their models, and found that the change in drift direction was not due to these factors. Therefore, they have considered two situations. In one of them, the model included a variation of the amount of water stored on land at a constant rate; the other took into account the acceleration of glacial melting over recent decades. It is in this second assumption that the hydrological component of the model produces the observed change in the direction of the drift, around 1995. The increase in groundwater extraction also seems to intervene, but to a lesser extent. A) Yes,

Reference: ” Polar Drift in the 1990s Explained by Terrestrial Water Storage Changes ,” by S. Deng, S. Liu, X. Mo, L. Jiang, and P. Bauer‐Gottwein, in Geophysical Research Letters , March 22, 2021.