Melting polar ice is slowing Earth's rotation, lengthening days, says study

A scientific paper has indicated that melting polar ice caps are redistributing mass around the equator, slowing Earth's rotation and lengthening days at an unprecedented rate

The impact of climate change, although widely known now, keeps springing more surprises with each passing day as newer studies emerge analysing the multi-faceted effect of the global phenomena. A new study published on Monday (July 15) indicates that the melting of polar ice caps is slowing the rotation of our planet, thereby lengthening our days at an unprecedented rate.

The research paper titled ‘The increasingly dominant role of climate change on length of day variations’, featured in the journal, Proceedings of the National Academy of Sciences. It revealed that the redistribution of water from Greenland and Antarctica is contributing to increased mass around the equator, news agency AFP cited one of the contributors Surendra Adhikari from NASA’s Jet Propulsion Laboratory, as saying.

 

Benedikt Soja of ETH Zurich compared this phenomenon to a figure skater extending her arms while spinning, which causes her rotation to slow down. Similarly, as the ice melts, the mass moves away from the Earth’s rotational axis, increasing its physical inertia and slowing its spin.

While Earth is often described as a sphere, it is more accurately an ‘oblate spheroid’, slightly bulging at the equator, similar to the shape of a satsuma. This shape is in constant flux due to various factors, including the daily tides affecting the oceans and crust, the slow drift of tectonic plates, and sudden, violent changes caused by earthquakes and volcanic activity.

How did the study come to this conclusion?

The study utilised observational techniques such as Very Long Baseline Interferometry, which measures the time difference in radio signals from space reaching different points on Earth, to determine variations in the planet's orientation and day length. Additionally, it employed the Global Positioning System (GPS) for precise measurements of Earth's rotation, accurate to within one-hundredth of a millisecond, and analysed ancient eclipse records dating back millennia.

Will it affect space travel?

The findings have significant implications for space travel. If Earth's rotation slows, the length of the day will increase by a few milliseconds beyond the standard 86,400 seconds. Currently, the Moon's gravitational pull, through tidal friction, is the more prominent cause of this slowdown, contributing to a gradual deceleration of 2.40 milliseconds per century over millions of years, the study showed.

Surprising findings of the study

However, the study presents a surprising conclusion: if greenhouse gas emissions continue at high levels, the effect of a warming climate on Earth's rotation will surpass that of the Moon's pull by the end of the 21st century. Adhikari noted that since 1900, climate change has extended the length of days by approximately 0.8 milliseconds. 

Under a worst-case scenario of high emissions, climate change alone could make days 2.2 milliseconds longer by 2100, the study noted.

Although these changes may seem negligible and imperceptible to humans, they have substantial implications for space and Earth navigation. Precise knowledge of Earth's orientation is crucial for communication with distant spacecraft, such as the Voyager probes, where even a minor deviation can result in significant navigational errors over vast distances.

[With inputs from agencies]