New research has uncovered that heavy rainfall originating from the Atlantic Ocean is the primary driver of lake-filling events in the northwestern Sahara, challenging long-held assumptions about the region’s climate history.
The study, published in Hydrology and Earth System Sciences, finds that only the most intense and prolonged storms trigger lake-filling episodes, offering fresh insights into both past climate conditions and the potential impacts of future climate change.
Conducted by Joëlle Rieder of ETH Zurich under the supervision of Dr. Moshe Armon (Hebrew University), Dr. Franziska Aemisegger (University of Bern), and Dr. Elad Dente (University of Haifa), the study examines Sebkha El-Melah, a normally dry lake in western Algeria.
The findings provide a deeper understanding of extreme weather patterns that contribute to water accumulation in the Sahara, a region often considered one of the driest on Earth.
Key findings:
- Extreme Rainfall is Rare but Impactful: Between 2000 and 2021, hundreds of storms hit the lake’s drainage basin, but only six led to significant lake-filling events.
- Atlantic Storms, Not Monsoons: Contrary to past theories that monsoonal rains from the south were the primary moisture source, the study identifies extratropical cyclones near the North African Atlantic coast as the main drivers.
- Moisture Transport Mechanism: Rainfall events are influenced by upper-level atmospheric patterns, which enhance moisture transport deep into the Sahara, bypassing the Atlas Mountains.
- Recycling-Domino Effect: Successive atmospheric processes amplify moisture transport across the desert, leading to heavy rainfall episodes.
- Stationarity of Weather Systems: Storms that persist for around three days are more likely to result in lake-filling events.
These findings challenge conventional climate reconstructions, which previously attributed the Sahara’s prehistoric lakes and wetlands to monsoonal rainfall. Instead, the study highlights the critical role of Atlantic-origin storms, offering a new perspective on how past climates supported wetter conditions in the desert.
Implications for future climate change
As climate change intensifies, projected increases in extreme rainfall events could reshape the Sahara’s hydrology. The research suggests that Saharan lakes could fill more frequently due not only to higher precipitation levels but also to more frequent and intense storms. This shift could have profound consequences for ecosystems, water availability, and human settlements in the region.
By integrating climate science, meteorology, remote sensing, and hydrology, the study provides a framework for future research on desert water systems and climate variability, helping scientists better understand and predict hydrological changes in arid environments.
