PALEOCEANOGRAPHY, VOL. 18, NO. 1, 1011, doi:10.1029/2002PA000791, 2003

The 41 kyr world: Milankovitch's other unsolved mystery

Maureen E. Raymo

Department of Earth Sciences, Boston University,
Boston, Massachusetts, USA

Kerim Nisancioglu

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology,
Cambridge, Massachusetts, USA

Abstract

[1]   For most of the Northern Hemisphere Ice Ages, from ~3.0 to 0.8 m.y., global ice volume varied predominantly at the 41,000 year period of Earth's orbital obliquity. However, summer (or summer caloric half year) insolation at high latitudes, which is widely believed to be the major influence on high-latitude climate and ice volume, is dominated by the 23,000 year precessional period. Thus the geologic record poses a challenge to our understanding of climate dynamics. Here we propose that variations in the insolation gradient between high and low latitudes control high-latitude climate and ice volume during the late Pliocene and early Pleistocene. The differential heating between high and low latitudes, driven by obliquity, controls the atmospheric meridional flux of heat, moisture, and latent energy, which may exert the dominant control on high-latitude climate on Milankovitch timescales. In the two-dimensional zonal energy balance models typically used to study the long-term evolution of climate, the meridional atmospheric moisture flux is usually kept fixed. The hypothesis that insolation gradients control the poleward energy fluxes, precipitation, and ice volume at high latitudes has never been directly examined within the context of an ice sheet model. In light of what we know about modern energy fluxes and their relative influence on high-latitude climate, this possibility should be examined.

Received 26 March 2002; revised 5 September 2002; accepted 19 September 2002; published 6 March 2003.

Keywords: Milankovitch, orbital variations, ice ages, Pleistocene, obliquity, paleoclimate.

Index Terms: 4267 Oceanography: General: Paleoceanography; 1620 Global Change: Climate dynamics (3309); 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 3359 Meteorology and Atmospheric Dynamics: Radiative processes.


AGU

Citation: Raymo, M. E., and K. Nisancioglu, The 41 kyr world: Milankovitch's other unsolved mystery, Paleoceanography, 18(1), 1011, doi:10.1029/2002PA000791, 2003.