Small shifts in the Earth's axis, discovered several decades ago, turned out to be associated not only with the completion of glaciation, but also with the movement of mantle flows and the redistribution of the mass of water in the oceans. This is the conclusion reached by geologists from NASA, who published an article in the journal Earth and Planetary Science Letters.
“Traditionally, it is believed that only the end of the ice age was the main reason for the recent displacements of the Earth's axis. We created a computer model of this process and found out that there are not one, but three sets of factors at once,”said Surendra Adhikari of NASA's Jet Propulsion Laboratory in Pasadena, USA.
The Earth, unlike most planets in the solar system, has a relatively stable axis. Thanks to the gravitational interaction of our planet and the Moon, the position of the axis has remained practically unchanged over the past several billion years, while the axes of Mars, Uranus and some large moons of the giant planets have shifted by tens of degrees.
Nevertheless, as observations at the end of the last century show, the Earth's axis is still slightly shifting - by about ten centimeters per year towards the 74th degree of west longitude. Many scientists believe that this is due to the end of the ice age and changes in the structure of the ice cap. However, others point out that such processes are clearly not enough to explain the current rate of displacement.
Adhikari and his colleagues created a computer model of the Earth's interior, taking into account how various processes in the lithosphere and hydrosphere affect the position of the axis, and found that the share of the "legacy of glaciation" accounts for only a third of all its displacements.
Scientists drew attention to the fact that the distribution of matter inside our planet depends not only on how hard the ice cap presses on its surface and where it is located, but also on how the mantle flows in the deep layers of the interior, as well as on the distribution of water on oceans, rivers and soil.
By combining data from seismic measurements, climatic satellites and other monitoring systems for the work of the subsoil, geologists calculated how these factors affect the movement of the axis. To their surprise, it turned out that the influence is relatively equal, and each of the factors explains the shifts by about a third.
In particular, scientists have found evidence that the draining of soils in the United States and India in the middle of the last century affected the position of the Earth's axis no less than the retreat of the ice of the northern polar cap and the melting of Greenland.
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All these processes, as noted by Adhikari, should be taken into account when making climate forecasts and assessing how global warming and retreat of glaciers may affect the appearance of the planet and its life in the near future.
