The “Hockey Stick” Imprint in Northwest African Speleothems

Lijuan Sha, Yassine Ait Brahim, Jasper A. Wassenburg, Jianjun Yin, Jiayu Lu, Francisco W. Cruz, Yanjun Cai, R. Lawrence Edwards, Hai Cheng

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present absolutely dated speleothem δ18O records spanning the past ∼1.5 kyr, which provide new evidence of the transmission of an anthropogenic signal to natural climatic archives in NW Africa. Combined with three other speleothem δ18O records from SW Morocco, the results indicate unprecedentedly dry conditions during the 20th century, which developed more rapidly than those during the Medieval Climate Anomaly (900–1350 CE), likely due to rising atmospheric CO2 levels. The 20th century drying evident in the speleothem records is consistent with the “Hockey Stick” pattern of increasing temperatures due to global warming. We demonstrate that this rapid drying is linked to warmer sea surface temperatures (SSTs) over the Azores High region, and cooler local SSTs off the coast of NW Africa. These changes intensified the Canary Current Upwelling, which promoted increased biological productivity in the surface water and enhanced the coastal fishing industry in Morocco.

Original languageEnglish (US)
Article numbere2021GL094232
JournalGeophysical Research Letters
Issue number17
StatePublished - Sep 16 2021

Bibliographical note

Funding Information:
This work was supported by grants from the NSFC (41888101, 41731174, 41561144003) and FAPESP 2017/50085‐3. J. A. Wassenburg acknowledges support from the Institute for Basic Science (IBS), Republic of Korea, under IBS‐R028‐Y2. We are grateful to Hanying Li and Xianglei Li for their help with the trace element analysis. The authors also thank the editor and reviewers for their constructive comments which have helped to improve the study.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.


  • Hockey Stick
  • Northwest Africa
  • SST
  • global warming
  • speleothems
  • upwelling


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