In this study, we present a Holocene rainfall index based on three high-resolution speleothem records from the Western Mediterranean, a region under the influence of the westerly winds belt modulated by the North Atlantic Oscillation (NAO). On centennial to millennial timescales, we show that the North Atlantic ice-rafting events were likely associated with negative NAO-like conditions during the Early Holocene and the Late Holocene. However, our data reveal that this is not clearly the case for the mid-Holocene ice-rafting events, during which we also show evidence of positive NAO-like patterns from other paleo-oceanographic and paleo-atmospheric data. Hence, contradictory mechanisms involving prolonged periods of both north and south shifts of the westerly winds belt (resembling positive and negative NAO-like patterns) might at least partially trigger or amplify the ice-rafting events and the slowdown of the Atlantic Meridional Overturning Circulation.
Bibliographical noteFunding Information:
The authors thank the Editor and the four anonymous reviewers for their constructive comments. This work was sponsored thanks to the National Natural Science Foundation of China (NSFC 41888101 and NSFC 41731174) to H. C., the Postdoctoral Science Foundation of China (2018M640971) to Y. A., Fundação de Amparo a Pesquisa do Estado de São Paulo, Brazil (FAPESP Grant 2017/50085‐3) and the CLIMACTE Tripartite Cooperative Project (IRD‐France/CNPq‐Brazil/ APGMV‐Africa 457400/2012‐9) grant to F. W. C. and A. S, the German Research Foundation (DFG) Grants WA3532/1‐1 to J. A. W. and DE 2398/3‐1 to M. D., and the U.S. National Science Foundation (NSF 1702816) to R. L. E. and H. C. We would like to thank Alyne Barros for her assistance with the stable isotope analyses and Li Hanying for her help with the statistical analyses. We are also grateful to Augusto Auler, Jean‐Loup Guyot, El Hassane Beraaouz, and the Associations of Speleologists in Agadir (ASS and ASA) for their help during fieldwork. The authors declare no conflict of interest.
©2019. American Geophysical Union. All Rights Reserved.
- Atlantic Meridional Overturning Circulation
- North Atlantic Oscillation
- North Atlantic ice-rafting
- Western Mediterranean