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Climate change causing a shift in Earth’s axis
Read more on - Polity | Economy | Schemes | S&T | Environment
- The story: Rising sea levels, heatwaves, melting glaciers and storms are some of the well-known consequences of climate change. New research has added yet another impact to this list – marked shifts in the axis along which the Earth rotates.
- Unusual movement: A new study published in 'Geophysical Research Letters' of the American Geophysical Union (AGU) says that due to the significant melting of glaciers because of global temperature rise, our planet’s axis of rotation has been moving more than usual since the 1990s.
- The Earth’s axis of rotation is the line along which it spins around itself as it revolves around the Sun. The points on which the axis intersects the planet’s surface are the geographical north and south poles.
- The location of the Earth's poles is not fixed, however, as the axis moves due to changes in how the Earth’s mass is distributed around the planet. Thus, the poles move when the axis moves, and the movement is called “polar motion”.
- According to NASA, data from the 20th century shows that the spin axis drifted about 10 centimetres per year. Meaning over a century, polar motion exceeds 10 metres.
- Generally, polar motion is caused by changes in the hydrosphere, atmosphere, oceans, or solid Earth. But now, climate change is adding to the degree with which the poles wander.
- Latest findings: Since the 1990s, climate change has caused billions of tonnes of glacial ice to melt into oceans. This has caused the Earth’s poles to move in new directions. The north pole has shifted in a new eastward direction since the 1990s, because of changes in the hydrosphere (meaning the way in which water is stored on Earth). From 1995 to 2020, the average speed of drift was 17 times faster than from 1981 to 1995. Also, in the last four decades, the poles moved by about 4 metres in distance. The faster ice melting under global warming was the most likely cause of the directional change of the polar drift in the 1990s, the study says.
- Other causes: The other possible causes are (terrestrial water storage) change in non-glacial regions due to climate change and unsustainable consumption of groundwater for irrigation and other anthropogenic activities. While ice melting is the major factor behind increased polar motion, groundwater depletion also adds to the phenomenon. As millions of tonnes of water from below the land is pumped out every year for drinking, industries or agriculture, most of it eventually joins the sea, thus redistributing the planet’s mass.
- Knowledge centre:
- Mass of Earth - The Earth mass is a standard unit of mass in astronomy used to indicate the masses of other planets. One Solar mass is close to 3,33,000 Earth masses. The Earth mass excludes the mass of the Moon. The mass of the Moon is about 1.2% of that of the Earth, so that the mass of the Earth+Moon system is close to 6.0456×1024 kg. Most of the mass is accounted for by iron and oxygen (roughly 32% each), magnesium and silicon (roughly 15% each), calcium, aluminium and nickel (roughly 1.5% each).
- Precession of Earth's axis - The Earth's axis rotates (precesses) just as a spinning top does. The period of precession is about 26,000 years. So the North Celestial Pole will not always be point towards the same starfield. Precession is caused by the gravitational pull of the Sun and the Moon on the Earth.
- Earth's poles - The geographic North Pole has a fixed position. It corresponds to the northern intersection of the Earth’s rotational axis with the Earth’s surface. Its coordinates are thus “90 degrees north”. The compass needle we use actually aligns with the magnetic field of the Earth. This field originates because liquid iron located in the outer core of the Earth circulates and swirls in response to the internal temperature differences and rotation of the Earth. It shields the planet from dangerous radiation and particles from outer space, and it also possesses a north and south pole. These are defined as the two points where the magnetic field lines extend into the Earth perpendicular to its surface. One of these points is located in the northern hemisphere and the other in the southern hemisphere, but their positions are not exactly diametrically opposed on the globe. Neither of them can be assigned a fixed geographical position because, due to magnetic storms and constant variations in the circulation of iron in the liquid outer core, their locations are constantly changing. The North Magnetic Pole was discovered in 1831, located near the Boothia Peninsula in the Canadian Arctic. From there, it has since wandered to the northwest and is now moving at a speed of around 55 kilometres per year. It is currently located north of the 85th parallel in the middle of the Arctic Ocean and is approaching Russia.
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