Glacial cyclicity of the Earth has often been considered on 100,000 year timescales, particularly for the Late Pleistocene (~11,700 to 129,000 years ago) swapping between periods of extensive polar and mountain glacier ice sheets, to warmer interglacial periods when ice sheets and glaciers retreated, with subsequent sea level rise. This is thought to be related to three key drivers affecting the amount of solar radiation reaching Earth from the sun.
Termed Milankovitch cycles, eccentricity considers the shape of Earth’s orbit changing from circular to more elliptical over 100,000 year timescales, while obliquity refers to the varying ‘tilt’ of the planet’s axis between 22.1 and 24.5 degrees over 41,000 years (contributing to seasons) and precession, which in simple terms is the direction Earth’s axis is pointed and can make the contrast between seasons more extreme in one hemisphere compared to the other.
While the eccentricity cycle has been a major factor thought to drive glacial/interglacial cycles, newer research has suggested that they instead may result from a series of obliquity or precession cycles (especially as the former dominated up to 800,000 years ago). To test this theory, Bethany Hobart, a Doctoral Researcher at the University of California, and colleagues modeled the impacts of glacial termination on 23,000 and 41,000 year cycles.
Leave a reply