A short-term climate oscillation during the Holsteinian interglacial (MIS 11c): An analogy to the 8.2 ka climatic event?

摘要

To gain insights into the mechanisms of abrupt climate change within interglacials, we have examined the characteristics and spatial extent of a prominent, climatically induced vegetation setback during the Holsteinian interglacial (Marine Isotope Stage 11c). Based on analyses of pollen and vsrves of take sediments from Dethlingen (northern Germany), this climatic oscillation, here termed the "Older Holsteinian Oscillation" (OHO), lasted 220 years. It can be subdivided into a 90-year-long decline of temperate tree taxa associated with an expansion of Pinus and herbs, and a 130-year-long recovery phase marked by the expansion of Betula and Alnus, and the subsequent recovery of temperate trees. The climate-induced naturs of the OHO is corroborated by changes in diatom assemblages and δ~(18)O measured on biogenic silica Indicating an impact on the aquatic ecosystem of the Dethlingen paleolake. The OHO is widely documented in poiier. records from Europe north of 50° latitude and is characterized by boreal climate conditions with cole winters from the British Isles to Poland, with a gradient of decreasing temperature and moisture availability, and increased continentality towards eastern Europe. This pattern points to a weakened influer.ee of the westerlies and/or a stronger influence of the Siberian High. A comparison of the OHO with the 8.2 ka event of the Holocene reveals close similarities regarding the imprint on terrestrial ecosystems and the intergiacial boundary conditions. Hence, in analogy to the 8.2 ka event, a transient, meltwater-induced slowdown of the North Atlantic Deep Water formation appears as a plausible trigger mechanism for the OHO. If correct, meftwater release into the North Atlantic may be a more common agent of abrupt climate change during intergiaciais than previously thought. We conclude that meltwater-induced climate setbacks during interglacials prefersentally occurred when low rates of summer insolation increase during the preceding terminations facili sted the persistence of large-scale continental ice-sheets well into the interglacials.