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. Plain Language Summary Several paleoclimatic studies have revealed a long‐term trend toward drier conditions in NW Africa over the past several decades. However, the mechanisms responsible for the recurrent droughts in NW Africa remain unclear, due to the lack of relevant climatic information. We present new absolutely dated paleoclimate data based on stalagmite oxygen isotope records from NW Africa. The results show that an anthropogenic climate signal has been transmitted to stalagmites in NW Africa where the spatiotemporal distribution of water resources has been substantially altered by global warming during the 20th century. Key Points Speleothem δ18O records from NW Africa show a “Hockey Stick” pattern In NW Africa, the 20th century was drier than any other time during the past 1.5 kyr Global warming has resulted in intensified upwelling, enhancing Moroccan fisheries