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How did orbital changes influence the timing of Pleistocene ice ages?
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Quaternary
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Quaternary Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The timing of Pleistocene ice ages is primarily driven by Milankovitch cycles, which describe how periodic changes in Earth's orbital geometry alter the distribution of solar radiation across the planet. These cycles act as the "pacemaker" for glacial-interglacial transitions.123
Three primary orbital parameters influence these climatic shifts:
- Eccentricity: The 100,000-year cycle of Earth’s orbit shifting from nearly circular to more elliptical.13
- Obliquity: The 41,000-year cycle of changes in the tilt of Earth’s axis, which significantly impacts high-latitude seasonal radiation.13
- Precession: The 19,000- to 23,000-year "wobble" of Earth’s axis, which affects the timing of seasons relative to the planet's position in its orbit.13
Glaciations are hypothesized to initiate during periods of low summer insolation in the Northern Hemisphere, allowing winter snow to persist through the summer. Because these orbital changes alone are relatively small, they are amplified by feedback mechanisms, such as changes in albedo from increased snow cover and fluctuations in atmospheric carbon dioxide concentrations.14