Several factors cause the Earth’s axis to tilt. The melting of glaciers in the Northern Hemisphere gives the planet an extra twist.
Earth is tilting. The Earth’s axis changes its position by about ten centimeters per year over time. Even with this planetary effect, called true polar wandering, humanity now has a hand in the game. Climate change has arguably been the main reason why our planet has tilted in a slightly different direction since the 1990s. At least that’s what a working group headed by Shanshan Ding of the Chinese Academy of Sciences wrote in the Geophysical Research Letters.
The team used a mathematical model to study general axis drift. It migrates about ten centimeters per year towards the southwest. But that changed in the mid-1990s, when drift shifted about ten degrees to the east. The working group model now indicates that melting glaciers, especially in Greenland, is a major contributor.
Melting ice blocks may be the missing factor
The exact location of the Earth’s axis depends on the distribution of the planet’s mass. Throughout the year, it stumbles about several meters due to its irregular shape. In addition, long-term displacements of large blocks are causing the Earth to tip over at longer time scales. For several thousand years, the Earth’s axis has tilted at about 3.3 microseconds arcseconds per year, driven by currents in the Earth’s mantle and the slow rise of the Earth after the retreat of continental ice caps.
However, these effects are not changing fast enough to explain the change in trend trend over the past few decades. So experts suspected for a while that melted ice blocks were the missing factor.
Deng’s team has now separated the different influences on the Earth’s mass distribution and compared two scenarios. On the one hand, the motion of the Earth’s inclination was considered a function of the previous factors; On the other hand, it added the contribution of shrinking glaciers in the second scenario. It turns out that the movement of the axis gets the required east-facing component just by taking into account the melting ice.