Human activities are having a profound impact on the Earth and climate change has actually tilted our planet’s rotation.
Rotation and Revolution
We have all learned about Earth’s rotation and revolution when we were kids. Rotation means Earth turning around its own axis and takes up to 24 hours whereas revolution is the earth’s movement around the Sun and it takes 365 days, 5 hours, and 59 minutes. While there has been no change in Earth’s revolution around the Sun, there has been a lot of change in Earth’s rotation.
While some people think that a planet’s distance from the sun causes a change in climate, that is not the case with Earth. The seasons on Earth depend upon the planet’s axis of rotation that is tilted at an angle of 23.5 degrees. Scientists call it Earths obliquity. Now, after new research was done, it shows that even though Earth’s poles are always moving, climate change and human water use are causing the poles to move faster.
Since 1899, scientists observed that Earth’s axis of spin has been shifted about 34 feet (10.5 meters). A third of this tilt is due to the melting ice and rising sea levels, particularly in Greenland and this is due to anthropogenic climate change. Anthropogenic climate change means that humans are causing most of the current change in climate instead of the climate-changing on its own. Another third of the wobble is due to the expanding land masses as the glaciers retreat and lighten their load. The last portion is the fault of the slow churn of Earth’s mantle.
The rotation of any object is affected by how the weight it carries, is distributed. Earth’s weight distribution is ever-changing and the key influencer of this change is water since it’s so heavy. NASA started two supersensitive satellite missions which started in 2002. They were the Gravity Recovery and Climate Experiment (GRACE) and its successors; however, they have been decommissioned since 2017. But before they were decommissioned, the satellites analyzed the shifting weight on Earth.
American Geophysical Union
In the new research, the scientists were interested in the shifts in Earth’s tilt in the 1990s, which was before the satellite missions by NASA were put into place. According to a statement released by the American Geophysical Union (AGU), the researchers have turned their attention to the water itself and the measurements of ice loss and statistics on groundwater pumped out for humans to use. They combined this observation with the studies of how the poles drifted.
It was found that in 1995, polar drift changed direction completely. From 1995 to 2020, it was noted that the speed of the pole movement increased 17 times as compared to the average speed that was measured from 1981 to 1995. When the polar drift data was combined with the water data, the researchers showed that a lot of the pole movement was caused due to the loss of water from polar regions.
Research by NASA's Jet Propulsion Laboratory
Since the 1990s the space-based measurements have confirmed that the Earth’s axis of rotation has been drifting by a few centimeters per year in the direction of Hudson Bay which is in north-eastern Canada. There have been many pole-drift observations for decades and according to researchers at AGU, the phenomenon has been measured for 176 years. The data from those observations have been very helpful to the researchers now. “The findings offer a clue for studying past climate-driven polar motion,” says Suxia Liu, a hydrologist at the Chinese Academy of Sciences and corresponding author of the new study.
Surendra Adhikari, an Earth system scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and is also a lead researcher on another axis rotation study. He and his colleagues published their research in the Earth and Planetary Science Letter which stated that glacial isostatic was only responsible for around 1.3 inches (3.5 centimeters) of axis wobble per year.
The researchers also built a computer model of the physics of Earth’s spin. They put in the data regarding changes in the balance of land-based ice and ocean waters. They even accounted for other such shifts in land and water, like the groundwater depletion and the artificial reservoirs which are built as humanity’s plan for terraforming the planet. Terraforming is the process of deliberately modifying the atmosphere, temperature, surface topography, etc, of a planet of any such body so that it has an Earth-like environment. Well, we wouldn’t have to do any terraforming if we took care of Mother Earth like she takes care of us, would we?
Anyways, the result of the model was that the environmental processes which were believed to have caused the tilt are in fact causing the tilt. Since the glaciers and the ice melt left a third of the cause of wobble still unanswered, Adhikari and his team looked inside the Earth’s mantle. He said that the mantle was not static, but does move by the process of convection i.e., hotter material that is closer to the core, rises, and the cooler material sinks in a vertical motion continuously. This helped them complete their research and provided an explanation for why and how climate change has affected Earth’s tilt.