PERSPECTIVES ATMOSPHERE Antarctica’s Orbital Beat
Alternating glacial and interglacial conditions have dominated Earth’s climate for at least the past 800,000 years ( 1, 2). Such a global rhythm of glaciation is surprising—at least if summer solar radiation controls glaciation ( 3)—because variations in Earth’s orbit cause opposite changes in the i...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.405.1894 http://www.people.fas.harvard.edu/~phuybers/Doc/beat_science2009.pdf |
| Summary: | Alternating glacial and interglacial conditions have dominated Earth’s climate for at least the past 800,000 years ( 1, 2). Such a global rhythm of glaciation is surprising—at least if summer solar radiation controls glaciation ( 3)—because variations in Earth’s orbit cause opposite changes in the intensity of northern and southern summer radiation. Deciphering the origins of the orbital period variations found in Antarctic proxies of climate may tell us why glaciations are global. Earth’s orbit around the Sun is not steady. The tilt of its spin axis varies with a period of 41,000 years, the eccentricity of its orbit changes at time scales of 100,000 to 400,000 years, and the orientation of the eccentric orbit precesses with respect to the seasons about once every 21,000 years. One implication of the orbital geometry is that at the time when precession aligns Earth’s closest approach to the Sun (perihelion) with Northern Hemisphere summer, Earth is farthest away from the Sun (at aphelion) during Southern Hemisphere summer. But if the north and south are alternately |
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