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Identifying Dansgaard/Oeschger Cycles during the Penultimate Glacial

Subject Area Palaeontology
Term from 2016 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 322834905
 
Final Report Year 2020

Final Report Abstract

The North Atlantic realm witnessed rapid and high-amplitude millennial-scale climate variations during the last glacial known as Dansgaard – Oeschger (D/O). These sudden events of strong NH warming lasted a few hundred to at most a few thousand years and interrupted cold stadials abruptly. Temperatures in Greenland increased by up to ~15°C within few decades. Following a slow decrease in temperature the final return to stadial conditions was rapid again. D/O events have been recognized world-wide, although their influence vanishes with increasing distance from the North Atlantic. The forcing mechanisms of D/O events are intensively debated, but there is general consensus that the interplay between extended Northern Hemisphere ice sheets and the Atlantic Overturning Circulation (AMOC) plays a central role. So far, however, robust knowledge of D/O events is only available for the last glacial period, from ice in Greenland and from a number of other proxy records. However, information about D-O events during earlier glacial periods and their absence would be extremely useful to obtain a more comprehensive picture of these enigmatic warmings. The aim of this study is to test if the D/O events, which occurred during the penultimate glacial, where different from those of the last glacial. We present replicated stable isotope records of speleothems from the northern rim of the European Alps. This location has previously shown to provide reliable evidence of D-O events for the last glacial period. Between ~202 and ~133 ka before present this record reveals three distinct eight ka-long periods without D/O variability. As during the last glacial period, these periods stopped when the global sea-level rose, suggesting that the triggering mechanism of D/O-events may is indeed sensitive to the continental ice-sheet extent.

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