The 8.2 ka event is a well-known cooling event in the Northern Hemisphere, but is poorly understood in Madagascar. Here, we compare paleoclimate data and outputs from paleoclimate simulations to better understand it. Records from Madagascar suggest two distinct sub-events (8.3 ka and 8.2 ka), that seem to correlate with records from northern high latitude. This could indicate causal relationships via changes in the Atlantic Meridional Overturning Circulation (AMOC) with changes in moisture source's δ18O, and changes in the mean position of the Inter-Tropical Convergence Zone (ITCZ), as climate modelling suggests. These two sub-events are also apparent in other terrestrial records, but the climatic signals are different. The prominent 8.2 ka sub-event records a clear antiphase relationship between the northern and southern hemisphere monsoons, whereas such relationship is less evident during the first 8.3 ka sub-event. Data–model comparison have also shown a mismatch between the paleoclimate data and the model outputs, the causes of which are more or less understood and may lie in the proxies, in the model, or in both data and model. Knowing that paleoclimate proxies and climate models produce different sets of variables, further research is needed to improve the data–model comparison approach, so that both paleoclimate data and paleoclimate models will better predict the likely climate status of a region during a specified time in the past with minimal uncertainties.
Bibliographical noteFunding Information:
This research was supported by the following grants: (1) the National Natural Science Foundation of China (NSFC 41731174 and 41561144003 ) to Hai Cheng, (2) the NERC grant NE/L002574/1 to Ilkka S.O. Matero, (3) the Geological Society of America Research Grant ( GSA 11166-16 ) and John Montagne Fund Award to N. Voarintsoa, (4) the Miriam Watts-Wheeler Graduate Student Grant from the Department of Geology at UGA to N. Voarintsoa, (5) the International Association of Sedimentology Post-Graduate Grant to N. Voarintsoa, and (6) grant NSF 1702816 to R. Lawrence Edwards and Hai Cheng. We also thank the Schlumberger Foundation for providing additional support to N. Voarintsoa's research. We thank the Department of Geology, Faculty of Science, at the University of Antananarivo, in Madagascar, the Ministry of Energy and Mines, the local village and guides in Majunga for facilitating our research in Madagascar. We specifically thank the former Department Head of the Department of Geology at the University of Antananarivo, for giving permission to do field expedition in Madagascar. We thank Prof. Paul Schroeder for giving us access to use the X-ray diffractometer of the Geology Department to conduct analysis on the mineralogy of Stalagmite ANJB-2. We thank Dr. Lixin Wang and Dr. Liz Keller for many productive discussions of the 8.2 ka event, and Dr. Joe Lambert for his prompt service analyzing our samples for stable isotopes. We thank Dr. Domínguez-Villar for sharing his Kaite Cave data with us. Finally, we thank Prof. Andy Baker for sharing unpublished δ 18 O metadata analyses of drip water, allowing us to better understand factors controlling δ 18 O in caves.
- 8.2 ka event
- Data–model comparisons
- Paleoclimate modeling
- Stable isotopes