Warm-cold oscillations during the last glacial period recorded in the oxygen isotope record of the Greenland ice, and also found in biotic and isotopic indices from deep-sea sediments in the North Atl
antic. The warm phases of these events correspond to interstadials, persist for a few hundred to a few thousand years, and have very rapid onset and termination (as little as a few decades). The range of temperature change inferred for the regions where the snow was formed that ultimately produced the Greenland ice was several degrees Celsius. Named for the ice core paleoclimatologists Willi Dansgaard and Hans Oeschger, Dansgaard-Oeschger events between 80 000 and 20 000 years ago are grouped in 10 000- to 15 000-year periods of increasing cooling. The ending of each of these groups of events is marked by a major flux of icebergs into the North Atlantic, as evidenced by associated material found in ocean floor sediments. The temperature conditions in Greenland and the North Atlantic region then return to the higher level of the beginning of the group of Dansgaard-Oeschger events. Most of the Dansgaard-Oeschger events that lasted 2000 years or more coincide with warmer conditions in East Antarctica, also revealed by analysis of oxygen isotopes in ice.
Abrupt events characterized in Greenland ice cores and in palaeoclimate records from the nearby North Atlantic by a cold glacial state, followed by a rapid transition to a warmer phase, and a slow coo
ling back to glacial conditions. Counterparts of Dansgaard-Oeschger events are observed in other regions as well.