Millennial variability and orbital influence on the last glacial inception
Abstract
The glacial inception that followed the prominent global warmth of marine isotope substage 5e (MIS 5e) marks the most recent transition from peak interglacial to glacial climate on Earth. It also followed the last interglacial interval to run its entire natural course, and the only such example of glacial onset for which quality paleoclimate records exist in ice cores, deep-sea sediment cores, and terrestrial sequences in both northern and southern hemispheres. We have combined the evidence from these climatic archives along with absolute dated records from corals and speleothems to assess the sequence and timing of events associated with the last glacial inception. This sequence includes a series of millennial oscillations of increasing magnitude within MIS 5e at high northern latitudes, and a subsequent cascade of events globally that implicate the oceanic and atmospheric circulation as well as the hydrological cycle in abrupt changes associated with the relatively slow decline in northern summer insolation. During the course of this transition, a threshold appears to have been crossed, possibly in the extent or location of incipient continental ice, triggering the dramatic millennial climate instability and bipolar pattern that characterized most of the ensuing 100,000 years until the completion of the last deglaciation. As during deglaciation, atmospheric greenhouse gas concentrations do not appear to have triggered the glacial inception, but rather served as a feedback mechanism that helped set the baseline conditions and the transition to a new glacial state, culminating eventually in the last glacial maximum.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMPP51F..04M
- Keywords:
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- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4926 PALEOCEANOGRAPHY / Glacial;
- 4936 PALEOCEANOGRAPHY / Interglacial;
- 4946 PALEOCEANOGRAPHY / Milankovitch theory