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Orgo-Life the new way to the future Advertising by AdpathwayThe repeated advance and retreat of ice sheets in North America and globally occurred as part of glacial–interglacial cycles, during which climate alternated between colder and warmer states. These were primarily driven by Milankovitch cycles1,2, which describe periodic changes in Earth’s orbit and orientation relative to the Sun, particularly affecting summer solar radiation in the Northern Hemisphere.
Although changes in solar radiation associated with orbital forcing are relatively small, their climatic effects were amplified by feedbacks within the climate system3, including changes in ice cover, greenhouse gas concentrations, and ocean circulation. Together, these processes created the conditions for repeated ice-sheet growth and decay.
Schematic illustration of the three main components of Milankovitch cycles: changes in Earth’s orbital shape (eccentricity), the tilt of Earth’s axis (obliquity), and the wobble of Earth’s axis (precession). Together, these variations alter the distribution of incoming solar radiation through time, particularly during Northern Hemisphere summers, and play a key role in pacing glacial–interglacial climate change. Image by Sciencia58, Wikipedia Commons.100,000 year cycles
Over the past million years, glacial–interglacial cycles have followed a dominant pattern of roughly 100,000 years5. However, the climate is never completely stable, and even within glacial periods there were fluctuations between colder stadial phases and relatively warmer interstadial phases.
These long- and short-term changes are captured in the Marine Isotope Stage (MIS) framework, a global climate record based on variations in oxygen isotopes preserved in deep-sea sediments, in which even-numbered stages correspond to colder stadial or glacial conditions and odd-numbered stages correspond to warmer interstadial or interglacial conditions5.
We are currently in an interglacial period known as the Holocene, which began around 11,700 years ago and corresponds to MIS 1.
More Information
NASA – Milankovitch Cycles
NASA – Why Milankovitch Cycles can’t explain current warming
Nature – Milankovitch cycles
About the Author
Jakob Hamann is an IAPETUS PhD student at Newcastle University, studying the former Cordilleran Ice Sheet.
References
1) Milankovitch, M. K. (1941). Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem. Royal Serbian Academy Special Publication, 133, 1-633.
2) Hays, J. D., Imbrie, J., & Shackleton, N. J. (1976). Variations in the Earth’s Orbit: Pacemaker of the Ice Ages: For 500,000 years, major climatic changes have followed variations in obliquity and precession. Science, 194(4270), 1121-1132.
3) Budyko, M. I. (1969). The effect of solar radiation variations on the climate of the Earth. Tellus, 21(5), 611-619.
4) Sciencia58. Earth’s orbit parameters for the Milankovitch cycles. Wikimedia Commons. Public domain (CC0 1.0). https://commons.wikimedia.org/wiki/File:Earth%27s_orbit_parameters_for_the_Milankovitch_cycles.png.
5) Lisiecki, L. E., & Raymo, M. E. (2005). A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography, 20(1).
6) Batchelor, C. L., Margold, M., Krapp, M., Murton, D. K., Dalton, A. S., Gibbard, P. L., … & Manica, A. (2019). The configuration of Northern Hemisphere ice sheets through the Quaternary. Nature communications, 10(1), 3713.
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