Here we present a new composite record from two well-dated speleothem records from two caves in Northern Morocco. The high-resolution record covers the last millennium allowing to detect multi-decadal to centennial periodicities. Over the industrial period, δ18O values of our speleothems are shown to be dominated by the main mode of decadal variability in the North Atlantic region: the North Atlantic Oscillation (NAO). Statistical analyses confirm the previously reported multi-decadal variability related to the influence of the Atlantic Multidecadal Oscillation (AMO) in the region. High power and persistent centennial-scale periodicities, similar to the Vries-Suess 200-year solar cycle, are observed as well. Indeed, comparison between solar activity reconstructions and our record confirms the in-phase relationship on centennial time-scales. Low δ18O values, and hence negative phases of NAO that bring precipitation towards the Western Mediterranean, are observed during well-known solar minima periods. The results are consistent with previous models which describe low irradiance as a trigger for southward shifts of precipitation-bearing westerlies during winter.
|Original language||English (US)|
|State||Published - Dec 1 2018|
Bibliographical noteFunding Information:
This work was sponsored thanks to the National Natural Science Foundation of China grants (NSFC 41731174 and NSFC 41561144003), the German Research Foundation (DFG: WA3532/1-1 and IM44/1) and the U.S. National Science Foundation (NSF Grant 1702816). We would like to express our deep gratitude to Dr. Myriam Khodri for the discussion about NAO and AMO influence in the Western Mediterranean region. We would also like to thank Professor El Hassane Beraaouz and the Associations of Speleologists of Agadir (ASA and ASS) for their help with the field work, Alyne Barros for her help with stable isotope analyses, and Dr. Raimund Muscheler for sharing their solar forcing reconstruction data. We thank the editor and the anonymous reviewers for their constructive comments.
© 2018, The Author(s).