Auswirkungen von Klimavariabilität auf terrestrische Ökosysteme in Südosteuropa während MIS 12-11 und MIS 19 anhand hochauflösender Pollenanalysen der Ohridsee-ICDP-Kernsedimente
Zusammenfassung der Projektergebnisse
The Middle Pleistocene (c. 800–130 ka) represents a critical interval of Quaternary climate evolution because it allows the study of climate change under both extreme glacial (i.e., during MIS 12) and interglacial (i.e., during MIS 11) conditions. It also includes the two most recent interglacials that occurred under similar orbital configuration as the Holocene (i.e., MIS 11 and 19), which can yield insight into the natural climate evolution of the present interglacial in the absence of human influence. To unravel climate and terrestrial ecosystem variability in Europe during MIS 11, 12 and 19, we have palynologically studied new core material from Lake Ohrid that was recovered within an ICDP drilling campaign. Our centennial-scale palynological results (mean resolution: 460 yrs) and pollen-based temperature and precipitation estimates were integrated with available sedimentological and geochemical proxy datasets from Lake Ohrid and compared with terrestrial and marine records from the Mediterranean and North Atlantic regions. For MIS 11, a c. 25-kyrs-long forest phase during the warmest MIS 11c substage was followed by a series of forest-contraction events each lasting 0.9–2.5 kyrs during the MIS 11a-b substages. While four of these forest contractions (at ~399, ~390, ~382.5, and ~376.5 ka) have counterparts in marine records suggesting a close coupling of terrestrial ecosystem dynamics between SE Europe and the North Atlantic, two other forest contractions (at ~395 and ~380 ka) have not been yet registered in marine proxy datasets, pointing to changes in atmospheric circulation enhancing dry conditions as the underlying mechanism. Notably, the first forest contraction at Lake Ohrid occurred within full interglacial conditions (at ~405 ka) suggesting that the onset of millennial-scale climate variability during MIS 11 in SE Europe pre-dates the first strong IRD event in the North Atlantic by ~15 ka. For MIS 12, a series of short-term forest contractions and expansions can be correlated with previously described SST fluctuations in the North Atlantic. Specifically, ten forest-expansion events registered at Lake Ohrid are correlative with interstadial (D-O-like) warming events; likewise, ten forest contractions indicate stadial events during MIS 12 that have been documented in North Atlantic SST records and partially also in IRD pulses. The close correspondence between forest-expansion/contraction events at Lake Ohrid and interstadial/stadial events in the North Atlantic suggests a close coupling of the atmospheric circulation over SE Europe to the variability of the North Atlantic Ocean circulation. Importantly, the millennial-scale variability in our pollen record was most pronounced when relative sea level was between c. -30 and -100 m, and it ceased when relative sea level dropped below -100 m. For MIS 19c, the duration of the forest phase lasted for ~15 kyrs, which is comparable to the duration of the Holocene, but shorter than MIS 11c. Interestingly, the expansion of thermophilous trees during MIS 19c was weaker than both during MIS 11c and the Holocene. This finding challenges the comparability of MIS 19c and the Holocene as to terrestrial ecosystem dynamics despite the close orbital analogy between the two periods. Finally, our palynological results confirm the presence of several tree taxa during all three studied intervals that are either now extinct from continental Europe or comprise Tertiary relics, supporting the view that the Lake Ohrid area has acted as a tree refugium during the Middle Pleistocene, and that the area has experienced later tree extirpations than other localities across the Mediterranean region.
Projektbezogene Publikationen (Auswahl)
- 2018. Centennial-scale vegetation dynamics and climate variability in SE Europe during Marine Isotope Stage 11 based on a pollen record from Lake Ohrid. Quaternary Science Reviews 190, 20–38
Kousis, I., Koutsodendris, A., Peyron, O., Leicher, N., Francke, A., Wagner, B., Giaccio, B., Knipping, M., Pross, J.
(Siehe online unter https://doi.org/10.1016/j.quascirev.2018.04.014) - 2019. Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature 573, 256–260
Wagner, B., Vogel, H., Francke, A., Friedrich, T., Donders, T., Lacey, J., Leng, M., Regattieri, E., Sadori, L., Wilke, T., Zanchetta, G., Albrecht, C., Bertini, A., Combourieu- Nebout, N., Cvetkoska, A., Giaccio, B., Grazhdani, A., Hauffe, T., Holtvoeth, J., Joannin, S., Jovanovska, E., Just, J., Kouli, K., Kousis, I., Koutsodendris, A., Krastel, S., Leicher, N., Levkov, Z., Lindhorst, K., Masi, A., Melles, M., Mercuri, A.M., Nomade, S., Nowaczyk, N., Panagiotopoulos, K., Peyron, O., Reed, J.M., Sagnotti, L., Sinopoli, G., Stelbrink, B., Sulpizio, R., Timmermann, A., Tofilovska, S., Torri, P., Wagner-Cremer, F., Wonik, T., Zhang, X.S.
(Siehe online unter https://doi.org/10.1038/s41586-019-1529-0) - 2019. The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions. Quaternary Science Reviews 221, 105873
Koutsodendris, A., Kousis, I., Peyron, O., Wagner, B., Pross, J.
(Siehe online unter https://doi.org/10.1016/j.quascirev.2019.105873)
