Melting ice slows Earth’s spin, lengthens days
Washington, United States: It’s well known that as far as the climate crisis goes, time is of the essence.
Now a study out Monday shows that the melting of the polar ice caps is causing our planet to spin more slowly, increasing the length of days at an “unprecedented” rate.
The paper, published in Proceedings of the National Academy of Sciences, shows that water flowing from Greenland and Antarctica is resulting in more mass around the equator, co-author Surendra Adhikari of NASA’s Jet Propulsion Laboratory told AFP.
“It’s like when a figure skater does a pirouette, first holding her arms close to her body and then stretching them out,” added co-author Benedikt Soja of ETH Zurich.
“The initially fast rotation becomes slower because the masses move away from the axis of rotation, increasing physical inertia.”
Earth is commonly thought of as a sphere, but it's more accurate to call it an “oblate spheroid” that bulges somewhat around the equator, a bit like a satsuma.
What’s more, its shape is constantly changing, from the impacts of the daily tides that affect the oceans and crusts, to longer term effects from drift of tectonic plates, and abrupt, violent shifts caused by earthquakes and volcanoes.
The paper relied on observational techniques like Very Long Baseline Interferometry, where scientists can measure the difference in how long it takes for radio signals from space to reach different points on Earth, and use that to infer variations in the planet’s orientation and length of day.
It also used the Global Positioning System, which measures Earth’s rotation very precisely, to about one-hundredth of a millisecond, and even looked at ancient eclipse records going back millennia.
Implications for space travel
If the Earth turns more slowly, then the length of day increases by a few milliseconds from the standard measure of 86 400 seconds.
A currently more significant cause of slowdown is the gravitational pull of the Moon, which pulls on the oceans in a process called “tidal friction” that has caused a gradual deceleration of 2.40 milliseconds per century over millions of years.
But the new study comes to a surprising conclusion that, if humans continue to emit greenhouse gases at a high rate, the effect of a warming climate will be greater than that of the Moon’s pull by the end of the 21st century, said Adhikari.
Between the year 1900 and today, climate has caused days to become around 0.8 milliseconds longer -- and under the worst-case scenario of high emissions, climate alone would be responsible for making days 2.2 milliseconds longer by the year 2100, compared to the same baseline.
That might not sound like a great deal, and certainly not something that humans are able to perceive.
But “there are definitely a lot of implications for space and Earth navigation”, said Adhikari.
Knowing the exact orientation of Earth at any given moment is crucial when attempting to communicate with a spaceship, such as the Voyager probes that are now well beyond our solar system, where even a slight deviation of a centimetre can end up being kilometres off by the time it reaches its destination.
Agence France-Presse
Vital ocean current at risk of collapse
A new study suggests that the Atlantic Meridional Overturning Circulation (AMOC) – the main ocean current system in the Atlantic Ocean – could tip towards collapse around 2050.
AMOC delivers heat to the gulf stream, carrying warm, nutrient-rich saline water north towards the pole where it cools and sinks, but the accelerated melting of Greenland’s ice cap as well as glacial run-off is increasingly smothering the current.
The collapse of the AMOC is one of five key climate tipping points, including the collapse of ice sheets in Greenland and the West Antarctic, the widespread thawing of permafrost, the death of coral reefs in warm waters.
Permafrost thawing, coral reef death among other key climate tipping points impacted by ice melt.
It would likely disrupt monsoons in India, and lead to drought in South America and west Africa, while temperatures in northern Europe would experience a sudden, severe drop and storms would increase.
Sea levels on the North American east coast would rapidly rise by about two feet, and part of the Amazon rainforest would dry out. The transport of essential nutrients to the North Atlantic would grind to a halt, threatening marine life.
Graphic News