Monday May 15, 2017 Q&A

Why is the North Pole drifting towards Europe?

Réponses

1 Because the Earth’s rotational rate is slowing down

2 Because of global warming

3 Because it’s pushed around by solar winds

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The correct answer is: 2. Because of global warming. The Earth doesn’t spin in a perfect circle. Its rotational movements around its own axis as well as on its path around the Sun are subject to a number of oscillations. These are most often caused by the gravitational pull of nearby bodies, such as the Moon, the Sun, and big planets like Jupiter. The phenomenon is similar to a spinning top that, once spinning, begins to drift as it encounters air currents. But the comparison is not quite correct. Because unlike a spinning top, our planet is not a completely rigid object — its surface can be deformed because it is made up of moving masses of air and water. These characteristics have an influence on the Earth’s rotation, according to scientists at Caltech and NASA’s Jet Propulsion Laboratory in California, who in a 2016 study described an unusual movement of the geographical north and south poles that dates to the start of the new millennium. The two geographical poles represent locations where the Earth’s axis of rotation crosses the planet’s surface, and they are not fixed. Their position, which has been the subject of numerous precise measurements dating from the late 19th century, is always changing. But up until recently, these changes occurred in a consistent manner, and always according to precise and predictable models. Since 2005, however, scientists have observed an unexpected change in the direction of the trajectory of the North Pole. It had been drifting in the direction of Montreal, Canada at a rate of about 6 cm per year, but suddenly took a turn to the East, heading for Greenland and Europe, and accelerating to 27 cm per year. A new equilibrium According to the scientists, it’s definitely the effect of global warming. To understand the cause of the phenomenon, the JPL team used data provided from 2003-2015 by the GRACE satellites (Gravity Recovery And Climate Experiment) whose mission was to measure variations in the Earth’s gravitational field and distribution of its surface masses. Their analysis of the satellite data showed that this change in the North Pole’s drift coincided exactly with the beginning of the warmest decade ever recorded, in which the melting of the icecaps, most notably in the Arctic, began to accelerate rapidly. Since then we have been witnessing a transfer and a redistribution of masses of water present in the atmosphere, seas, oceans, ice caps and polar sea ice. In addition to melting ice, the scientists point to the large scale movement of groundwater, in particular lakes and bodies of water that are drying up in Europe and Asia, notably in the Caspian Sea region and in India. This is what is causing the axis of rotation to slide towards the east, since it logically tends to aim towards areas in which a loss of water has occurred. In addition, increasing temperatures have also caused increased overall evaporation, changing the balance of water between the surface and the atmosphere. Thanks to James Badro, scientist in EPFL’s Earth and Planetary Sciences Laboratory.