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The massive melting of glaciers as a result of global warming has caused marked changes in the Earth’s axis of rotation since the 1990s, research has shown. This demonstrates the profound impact humans have on the planet, scientists said.
The planet’s geographic north and south poles are the point where its axis of rotation intersects the surface, but they are not fixed. Changes in the distribution of land mass around the planet cause the axis to shift, and therefore the poles.
In the past, only natural factors such as ocean currents and the convection of hot rocks in the depths of the Earth contributed to the drift position of the poles. But new research shows that since the 1990s, the loss of hundreds of billions of tonnes of ice per year in the oceans as a result of the climate crisis has caused the poles to shift in new directions.
Scientists found that the direction of the polar drift shifted from south to east in 1995, and that the average drift speed from 1995 to 2020 was 17 times faster than from 1981 to 1995.
Since 1980, the position of the posts has moved about 4 meters apart.
“The accelerated decline [in water stored on land] resulting from melting glacial ice is the main driver of the rapid polar drift after the 1990s, ”concluded the team, led by Shanshan Deng, of the Institute of Geographic Sciences and Natural Resources of the Chinese Academy of Humanities. science.
Gravity data from the Grace satellite, launched in 2002, had been used to relate glacier melt to pole movements in 2005 and 2012, both as a result of increased ice loss. But Deng’s research breaks new ground by extending the link before the satellite’s launch, showing that human activities have shifted the poles since the 1990s, nearly three decades ago.
The research, published in the journal Geophysical Research Letters, showed that glacial loss accounted for most of the change, but it is likely that pumping of groundwater also contributed to the movements.
Groundwater is stored underground but, once pumped for consumption or agriculture, most of it eventually flows to the sea, redistributing its weight around the world. Over the past 50 years, humanity has removed 18 tonnes of water from deep underground reservoirs without being replaced.
Vincent Humphrey, of the University of Zurich, Switzerland, and not involved in the new research, said he was showing how human activities have redistributed huge amounts of water around the planet: can shift the axis of the earth. However, the movement of the Earth’s axis is not large enough to affect daily life, he said: it could change the length of a day, but only by a few milliseconds.
Professor Jonathan Overpeck, of the University of Arizona, United States, previously told the Guardian that the changes in the Earth’s axis highlight “how much of a real and profound impact humans have on the planet”.
Some scientists say the magnitude of this impact means that a new geological epoch – the Anthropocene – must be declared. Since the mid-twentieth century, there has been a marked acceleration in carbon dioxide emissions and sea level rise, destruction of wildlife and transformation of land through agriculture, deforestation and land use. development.
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