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Title: What causes abrupt Dansgaard-Oeschger warmings during glacial periods?
Plain: During the last ice age Greenland repeatedly warmed by 8 to 16 degrees within a few decades, then slowly cooled again, about 25 times. The trigger of these jumps, called Dansgaard-Oeschger events, is unknown.
Precise: For the Greenland interstadial onsets of the last glacial period (about 115 to 12 kyr ago), determine whether the abrupt warmings are noise-induced transitions between AMOC states, self-sustained oscillations involving sea-ice and ocean stratification in the Nordic Seas, or forced by ice-sheet changes, and what sets their irregular spacing. An answer is a mechanism reproduced in a comprehensive model under glacial boundary conditions with the observed amplitude, rise time of decades, and Antarctic bipolar seesaw lag.
Settled by: Spontaneous Dansgaard-Oeschger-like cycles in comprehensive coupled models whose controlling variable is confirmed by high-resolution marine and ice-core proxies across events.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)