A 0.5-Million-Year Record of Millennial-Scale Climate Variability in the North Atlantic

+ See all authors and affiliations

Science  12 Feb 1999:
Vol. 283, Issue 5404, pp. 971-975
DOI: 10.1126/science.283.5404.971

You are currently viewing the abstract.

View Full Text


Long, continuous, marine sediment records from the subpolar North Atlantic document the glacial modulation of regional climate instability throughout the past 0.5 million years. Whenever ice sheet size surpasses a critical threshold indicated by the benthic oxygen isotope (δ18O) value of 3.5 per mil during each of the past five glaciation cycles, indicators of iceberg discharge and sea-surface temperature display dramatically larger amplitudes of millennial-scale variability than when ice sheets are small. Sea-surface temperature oscillations of 1° to 2°C increase in size to approximately 4° to 6°C, and catastrophic iceberg discharges begin alternating repeatedly with brief quiescent intervals. The glacial growth associated with this amplification threshold represents a relatively small departure from the modern ice sheet configuration and sea level. Instability characterizes nearly all observed climate states, with the exception of a limited range of baseline conditions that includes the current Holocene interglacial.

  • * To whom correspondence should be addressed. E-mail: jmcmanus{at}

View Full Text