Abstract:
High-resolution pollen records from the northern alpine foreland are used to evaluate the patterns of climate change during the period between the late Eemian Interglacial (marine oxygen isotope stage OIS 5e) about 115 ky ago and the end of the St. Germain II (OIS 5a, Dansgaard–Oeschger interstadial D/O IS21) about 75 ky ago. For the quantitative climate interpretation of the fossil pollen assemblages, we compare two different methods, a modern analogue technique and a mutual climatic range approach. The results not only reveal major climatic changes at the transition to stadials and interstadials, but also indicate short-term oscillations which are followed by an almost full return to the preceding climate conditions, and components of gradual trends resembling saw-tooth structures. Based on the pollen data, the climate reconstructions suggest that the optimum in St. Germain II (OIS 5a, D/O IS21) in winter temperatures was about 0.8 to 1.4 °C and in summer temperatures about 0.7 to 1.2 °C warmer than the optimum in St. Germain I (OIS 5c, D/O IS22 to IS24). The severe and short-time Montaigu cold event (iceberg discharge event C23) clearly divided St. Germain I into two thermal periods. Thus, St. Germain Ia (D/O IS24) preceding the Montaigu event is slightly more favourable than the following St. Germain Ic (D/O IS23). Since several climate oscillations occurred during these interstadials, they show only limited stability. With respect to the stadial periods, the results reveal a coherent pattern for all records. Winter temperatures during Melisey II (OIS 5b, C21) are about 1 to 4 °C lower than those during Melisey I (OIS 5d, C24). As regards short-term climate changes during Melisey I and Melisey II, consistent amelioration episodes may be distinguished during these intervals.
