Dansgaard–Oeschger event

Dansgaard - Oeschger events (short: DO ) events are rapid climate fluctuations during the last glacial period. 23 such events were found 110000-23000 BP. Dansgaard - Oeschger events are named after Willi Dansgaard and Hans Oeschger.

In the northern hemisphere they present themselves as periods of rapid heating followed by slow cooling dar. The process takes place over a longer period, which is typically described on scales of centuries.

Causes

The underlying process for the occurrence and amplitude of the event are still unclear. The effect of the event in the southern hemisphere with slower heating and much smaller temperature fluctuations differs significantly from that of the northern hemisphere. Therefore, the existence of the Dansgaard - Oeschger events took place only after the evaluation of the Greenland Eisbohrprojekte GRIP and Greenland Ice Sheet Project ( GISP ) wide acclaim, although evidence of the phenomenon already in the ice core, which was taken at the Vostok station, were found.

Dansgaard - Oeschger events are related to Heinrich events. Heinrich events are interruptions of the thermohaline circulation, causing a cooling in the Northern Hemisphere. A cooler climate results in an increase in ice coverage and thus a higher albedo of the earth's surface result in the enhanced cooling. There are indications that Dansgaard -Oeschger events occur globally synchronized.

In 2003, the climate scientist Stefan Rahmstorf identified a 1470 -year cycle in which the phenomenon occurred. As an explanation for the events was beaten in front of 2004 Ocean circulation modes. In a subsequent study, which was conducted in 2005, the periodicity of a superposition of two known activity cycles of the sun could be attributed. After 1470 years, therefore, the 210cc - cycle seven times, and the 86.5 he cycle is seventeen expired.

The deviations from this cycle were in the last 50,000 years as measured by the GISP2 about ± 12 % (± 2% in the five most recent events whose data can be captured very precisely ). However, neither older parts of the GISP2 core still comparable events in the GRIP core show such regularity, which could be explained for the first 50,000 years of the GISP2 core with varying degrees of reliability, especially closer layer count.

History

The Dansgaard -Oeschger anomalies are looking back in other cores ( GISP, Century Greenland ) to find. Dansgaard et al. noted the existence in the GRIP core as a "violent oscillations " in the δ18O signal that seemed to correlate 1400 km away with former Camp Century cores. Dansgaard et al. speculated that this could be related to the quasi-stationary modes of the atmosphere-ocean system.