Early onset and tropical forcing of 100,000-year Pleistocene glacial cycles

摘要: Between 1.5 and 0.6 Myr ago, the period of Earth's glacial cycles changed from 41 kyr, obliquity cycles, to 100 orbital eccentricity1,2, which has a much smaller effect on global insolation. The timing this transition its causes pose one most perplexing problems in palaeoclimate research3. Here we use complex demodulation examine phase evolution precession semiprecession cycles—the latter are phase-coupled both eccentricity—in tropical extra-tropical Atlantic Ocean. We find that about (with periods 11.5 kyr) started propagate higher latitudes, coincident with growing amplitude envelope 100-kyr cycles. Evidence numerical models suggests 10 kyr length may be required explain high cycles4. Combining our results consideration modern analogue, conclude increased heat flow across equator or tropics latitudes around ago strengthened cycle Northern Hemisphere, triggered sustained