Letters to Nature

Nature 434, 491-494 (24 March 2005) | doi:10.1038/nature03401; Received 6 August 2004; Accepted 24 January 2005

Obliquity pacing of the late Pleistocene glacial terminations

Peter Huybers1 & Carl Wunsch2

  1. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
  2. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

Correspondence to: Peter Huybers1 Correspondence and requests for materials should be addressed to P.H. (Email: phuybers@whoi.edu).

The 100,000-year timescale in the glacial/interglacial cycles of the late Pleistocene epoch (the past approx700,000 years) is commonly attributed to control by variations in the Earth's orbit1. This hypothesis has inspired models that depend on the Earth's obliquity (approx 40,000 yr; approx40 kyr), orbital eccentricity (approx 100 kyr) and precessional (approx 20 kyr) fluctuations2, 3, 4, 5, with the emphasis usually on eccentricity and precessional forcing. According to a contrasting hypothesis, the glacial cycles arise primarily because of random internal climate variability6, 7, 8. Taking these two perspectives together, there are currently more than thirty different models of the seven late-Pleistocene glacial cycles9. Here we present a statistical test of the orbital forcing hypothesis, focusing on the rapid deglaciation events known as terminations10, 11. According to our analysis, the null hypothesis that glacial terminations are independent of obliquity can be rejected at the 5% significance level, whereas the corresponding null hypotheses for eccentricity and precession cannot be rejected. The simplest inference consistent with the test results is that the ice sheets terminated every second or third obliquity cycle at times of high obliquity, similar to the original proposal by Milankovitch12. We also present simple stochastic and deterministic models that describe the timing of the late-Pleistocene glacial terminations purely in terms of obliquity forcing.


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