Younger Dryas‐Style Cooling Events at Glacial Terminations I‐VI at ODP Site 658: Associated benthic δ13C anomalies constrain meltwater hypothesis

American Geophysical Union (AGU) - Tập 5 Số 6 - Trang 1041-1055 - 1990
Michael Sarnthein, Ralf Tiedemann

Tóm tắt

High‐resolution planktonic and epibenthic stable isotope records from Ocean Drilling Program site 658 off northwest Africa provide a basis for a detailed study of glacial terminations I‐VI during the last 650,000 years. The duration of the terminations was about one half to one quarter of an orbital precession cycle (5800–10,700 years), when its amplitude was high. At low amplitudes, the terminations lasted longer than half an obliquity cycle (29,000 years). Marked climatic rebounds similar to the Younger Dryas, each with a duration of 1000–2500 years, subdivided all six terminations into distinct steps A, B, and C. Important parts of the deglacial steps were as brief as 700–1000 years. The speed of climatic change suggests that special associations existed between orbital forcing and inherent instability of the ice sheets. In harmony with published models, the more rapid pulses of glacial meltwater incursions to the northern North Atlantic led to one or more brief short‐term shut‐downs of North Atlantic Deep Water formation. This process is reflected by pronounced benthic δ13C minima that precisely coincide, in most cases, with the end of the δ18O deglaciation steps and immediately terminate with succeeding Younger Dryas‐style cooling events. Thus we conclude that the rebounds resulted from a short‐term antecedent estuarine circulation regime in the North Atlantic, except for the Younger Dryas itself, which succeeded the Alleröd with its well ventilated Atlantic deepwater circulation and hence continues to be an enigma.

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American Geophysical Union (AGU)

Tập 5 Số 6

1041-1055

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