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

Vandergoes MJ, Newnham RM, Preusser F, Hendy CH, Lowell TV, Fitzsimons SJ, Hogg AG, Kasper HU, Schlüchter C

Climate Change Institute, University of Maine, Orono, Maine 04469, USA. vandergoes@maine.edu

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.

Published 14 July 2005 in Nature, 436(7048): 242-5.
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