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Abstract:
Abrupt change is a major challenge for climate research because understanding the processes of rapid high-amplitude climate shifts is crucial for a better assessment of the likelihood of such changes in future. However, we still lack crucial knowledge about the triggers and dynamics of such shifts as well as about their impacts. It is even not clear yet if there are prognostic symptoms preceding abrupt changes which eventually might aid early warning. Since abrupt shifts in climate did not occur in historical times the only source of information are high resolution geological archives. First evidences show that in geological time scales abrupt climate shifts are more common than expected but mainly occurred during glacial periods. Annually layered lake sediments allow a precise year-by-year measure of the velocity of change and to decipher the underlying processes. In sediments from Lake Meerfelder
Maar the rapid temperature decline at the onset of the Younger Dryas 12 700 years ago was decoded using a novel methodology integrating microscope analyses with high resolution element scanning. A distinct shift in the sediment deposition from one year to the next reflects a sudden increase in storminess indicating a re-organisation of atmospheric circulation as a likely trigger. Hence, annually laminated lake records contribute to creating sophisticated knowledge about the nature of rapid climate changes including their triggering mechanisms, velocity, and impact on the human habitat.
