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A 0.5-Million-Year Record of Millennial-Scale Climate Variability in the North Atlantic
Ist Teil von
Science (American Association for the Advancement of Science), 1999-02, Vol.283 (5404), p.971-975
Ort / Verlag
Washington, DC: American Society for the Advancement of Science
Erscheinungsjahr
1999
Link zum Volltext
Quelle
American Association for the Advancement of Science
Beschreibungen/Notizen
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 ($\delta^{18}$O) 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.