The “Hockey Stick” Imprint in Northwest African Speleothems

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.