Earth is changing shape as polar regions rise and equatorial areas sink
Earth is not a perfect sphere. It is slightly flattened at the poles and wider around the equator. The new research shows that this shape is not fixed and is changing as ice melts and water and other surface masses are redistributed around the planet.
Researchers analyzed vertical movements of the Earth's surface using data from global Global Navigation Satellite System (GNSS) networks, covering the period from 1997 to 2015. They found that uplift in polar regions accelerated from about 0.5 millimeters per year in the late 1990s to nearly 1 millimeter per year in the later part of the study period. At the same time, equatorial regions experienced subsidence at a similar rate.
Together, these movements indicate that the solid Earth is becoming slightly less flattened. The researchers estimate that this change accelerated by about 0.4 millimeters per year per decade.
The study links the additional signal to contemporary loss of ice, particularly in polar regions. When ice melts, water moves from high latitudes toward lower latitudes and the oceans. This redistribution affects the Earth's surface and causes the solid ground to respond, including through uplift near the poles and subsidence in lower latitudes.
The researchers also examined changes in the Earth's gravity field through the parameter known as J2. Unlike GNSS measurements, which track the physical movement of the Earth's surface, J2 reflects changes in how mass is distributed around the planet. The results showed that changes in Earth’s shape accelerated in recent years, even after accounting for the long-term effects of melting glaciers.
The researchers say the apparently opposite changes are not contradictory. Ice loss can make the solid Earth's shape less flattened as the ground responds to changing surface loads, while the movement of mass toward lower latitudes can increase the equatorial concentration of mass and make the gravity field more oblate.
Earlier, Qazinform News Agency reported that Earth is at risk of geomagnetic storms.
