Australia: The Land Where Time Began

A biography of the Australian continent 

North Atlantic Millennial-Scale Climate Variability - A 0.5 My Record

The glacial modulation of regional climate instability over the past 0.5 My has been documented in long, continuous marine sediment records from the sub-polar North Atlantic. During each of the past 5 glacial cycles, whenever the size of ice sheets surpasses a critical threshold, as indicated by the benthic oxygen isotope (σ18O) value of 3.5 per mil, indicators of the discharge of icebergs and temperatures of the sea surface, dramatically larger amplitudes of variability on a millennial scale are displayed than when ice sheets are small. The temperatures of the surface waters that  oscillate between 1-2oC  increase to about 4-6oC, and discharge of icebergs on a catastrophic scale begin to alternate repeatedly with brief intervals of quiescence. A departure from the modern ice sheet configuration and sea level is represented by the glacial growth that is associated with this amplification threshold. Almost all observed climate states are characterised by instability, except for a limited range of baseline conditions, including the Holocene interglacial of the present.

Sources & Further reading

  1. McManus, J. F., D. W. Oppo, and J. L. Cullen. "A 0.5-Million-Year Record of Millennial-Scale Climate Variability in the North Atlantic." Science 283 (// 1999): 971-75.


Author: M. H. Monroe
Last Updated 07/07/2013
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