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Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere

Marcus J. Vandergoes1, Rewi M. Newnham2, Frank Preusser3, Chris H. Hendy4, Thomas V. Lowell6, Sean J. Fitzsimons7, Alan G. Hogg5, Haino Uwe Kasper8 and Christian Schlüchter3

1 Climate Change Institute, University of Maine, Orono, Maine, USA.
2 School of Geography, University of Plymouth, Plymouth, UK.
3 Institute of Geological Sciences, University of Bern, Bern, Switzerland.
4 Department of Chemistry, University of Waikato, Hamilton, New Zealand.
5 Radiocarbon Dating Laboratory, University of Waikato, Hamilton, New Zealand.
6 Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA.
7 Department of Geography, University of Otago, Dunedin, New Zealand.
8 Geologisches Institut, Universitat zu Köln, Köln, Germany.


Abstract

In agreement with the Milankovitch orbital forcing hypothesis it is often assumed that glacial-interglacial climate transitions occurred synchronously in the Northern and Southern hemispheres of the Earth. It is difficult to test this assumption, because of the paucity of long, continuous climate records from the Southern Hemisphere that have not been dated by tuning them to the presumed Northern Hemisphere signals. Here we present an independently dated terrestrial pollen record from a peat bog on South Island, New Zealand, to investigate global and local factors in Southern Hemisphere climate changes during the last two glacial-interglacial cycles. Our record largely corroborates the Milankovitch model of orbital forcing but also exhibits some differences: in particular, an earlier onset and longer duration of the Last Glacial Maximum. Our results suggest that Southern Hemisphere insolation may have been responsible for these differences in timing. Our findings question the validity of applying orbital tuning to Southern Hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change.

 

Reference

Vandergoes, M.J., Newnham, R.M., Preusser, F., Hendy, C.H., Lowell, T.V., Fitzsimons, S.J., Hogg, A.G., Kasper, H.U. and Schlüchter, C. 2005. Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere. Nature 436, 242-245. [PDF 394kb] doi: 10.1038/nature03826

 

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