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Dansgaard-Oeschger event

Idea

Dansgaard-Oeschger events are periods of abrupt climate change that have occurred 25 times during the last glacial period. In the Northern Hemisphere, they take the form of rapid warming episodes, typically in a matter of decades, each followed by gradual cooling over a longer period. The effect appears to be less in the Southern Hemisphere, as seen in this comparison of ice cores from Antarctica (above) and Greenland (below):

This suggests that Dansgaard-Oeschger events may be related to changes in the Atlantic meridional overturning circulation.

These events may drive the Sahara pump: the flow of vegetation, and then animals eating that vegetation, and then people hunting those animals, into and out of the Sahara as this region becomes alternately moister and drier. The Sahara pump may have had an important effect upon human evolution and dispersal, as discussed in the book The Long Summer.

Periodicity?

Some scientists claim that Dansgaard-Oeschger events occur quasi-periodically with a recurrence time being a multiple of 1,470 years, but this is debated. The comparable climate cyclicity during the Holocene is referred to under the term Bond events.

Questions

  • What is the relation between Dansgaard-Oeschger events and Heinrich events? The Wikipedia articles are a bit unclear about this.

  • What causes these events?

References

category: climate