The recent research published in the Geophysical Research Letters of the American Geophysical Union (AGU) reveals an interesting yet alarming fact about our planet. The Earth’s axis of rotation has been moving at an unexpected rate since the 1990s. This phenomenon is primarily due to the severe melting of glaciers triggered by the escalating global temperature. While this change is subtle and may not directly impact our daily operations, it potentially alters the length of our day by milliseconds.
Understanding the Earth’s Axis of Rotation
The Earth’s axis of rotation is an imaginary line around which our planet spins as it orbits the Sun. This axial tilt is approximately 23.5 degrees, also known as the obliquity of the ecliptic. Due to this specific tilt, sunlight strikes various latitudes at different angles throughout the year, generating seasonal variations. The points where the axis intersects the Earth’s surface are identified as the geographical north and south poles.
Interestingly, the position of these poles is not stagnant; they move in sync with any changes in the Earth’s mass distribution. Such shifts in the Earth’s axis lead to a phenomenon called “polar motion”. Polar motion is typically incited by alterations in the hydrosphere, atmosphere, oceans, or even solid Earth.
The Impact of Climate Change on Polar Motion
Today, climate change is increasingly influencing the degree of polar wander. NASA’s data from the 20th century states that the spin axis drifted approximately 10 centimetres annually. This means that over an entire century, the total polar motion crosses 10 meters.
Revelations from the Recent Study
The study established a direct correlation between climate change and the accelerated polar drift. Since the 1990s, the warming climate has caused billions of tonnes of glacial ice to melt and flow into the oceans. This redistribution of water mass has led the Earth’s poles to move in new, unprecedented directions.
Remarkably, the north pole has started shifting eastward since the 1990s due to changes in the hydrosphere or the method through which water is stored on Earth. During the period from 1995 to 2020, the average speed of this drift was found to be 17 times quicker than the period from 1981 to 1995. Furthermore, in the past four decades, the poles have shifted around 4 meters in distance.
The above calculations are based on satellite data obtained from NASA’s Gravity Recovery and Climate Experiment (GRACE) mission.
Decoding the Causes of Polar Drift
One major cause powering the polar drift is Ice Melting. The hastened ice melting brought about by global warming is the most plausible reason behind the polar drift’s directional change in the 1990s.
Changes in Non-Glacial Regions or Terrestrial Water Storage is another factor. This is predominantly due to climate change and unsustainable consumption of groundwater for irrigation and other human-induced activities. Lastly, Groundwater Depletion is also a contributing element. Millions of tonnes of water are extracted every year for drinking, industry, or agriculture. Most of this water eventually reaches the sea, thereby shifting the planet’s mass balance.
