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The Younger Dryas Event

The end of the Ice Age world started about 15,000 B.C. and brought great changes to the landscape, including sea-level rise.

[Temperatures of the Last 18,000 years]
Temperatures of the Last 18,000 years

However, the warmer climate was short lived. Between 12,800 and 11,500 years ago a short but severe cold spell occurred. This period was named the "Younger Dryas" event after a arctic/alpine flower Dryas Octopetald which had returned to Britain during this period.

At the beginning of the Younger Dryas, the global average temperature fell rapidly by about 2°C in under 50 years. In Northern Europe, average surface temperatures dropped by some 5°C. The much larger cooling in Northern Europe has been attributed to a change in the Atlantic Ocean circulation as outlined below.

Rapid ice melt
large amounts of of cold fresh water spreading into the North Atlantic
(Ocean circulation controlled by temperature and salinity)
Flow of the warm Gulf Stream into Europe stopped
Heat no longer carried into the area
Sudden and drastic drop in temperatures in the North Atlantic
Ice pack spread rapidly
Further cooling

After about 1000 years, the volume of cold fresh water decreased -> flow of tropical waters began again -> and rapid warming of global temperatures began. Over a period of 50 years or less the global averatge temperature increased by about 3°C, while temperatures over Northern Europe increased by 7°C.

This event is important for a number of reasons:

  1. It illustrates interrelationships between the different elements of the climate system. (In this case Ice melt, Ocean circulation, and continental temperatures).
  2. It demonstrates that major natural fluctuations in climate have occurred within the current interglacial period, although we consider the current interglacial as a relatively tranquil period in terms of climate change.
  3. It shows how sensitive climate can be, i.e., significant changes can occur quickly, in a matter of decades, rather than centuries. A possible caution for what could happen today if we alter climate due to the addition of greenhouse gases.

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