New research reveals that only the most intense Atlantic-sourced storms are responsible for filling a normally dry lake in the northwestern Sahara, overturning previous assumptions about monsoonal influences.
New research reveals that intense rainfall originating from the Atlantic Ocean is the main driver of modern lake-filling events in the northwestern Sahara. The study shows that only the most severe and long-lasting precipitation events lead to these rare lake formations, challenging previous assumptions about the region’s past climate. The findings suggest that projected increases in rainfall intensity and frequency across the Sahara could significantly impact future water availability in the desert.
The study, recently published in Hydrology and Earth System Sciences, was led by Joëlle Rieder at ETH Zurich, under the supervision of Dr. Moshe Armon (Hebrew University) and Dr. Franziska Aemisegger (University of Bern), in collaboration with Dr. Elad Dente (University of Haifa). It sheds new light on the meteorological mechanisms behind the filling of a typically dry lake in the northwestern Sahara. By linking present-day hydrological events to past climate patterns, the research offers valuable insights into how future climate change could shape water resources in arid regions.
The Sahara Desert, one of the driest places on Earth, has not always been as arid as it is today. Prehistoric evidence of wetlands in the Sahara points to wetter periods in the past, but scientists have long debated the sources of moisture responsible for these ancient water bodies. The study examines how the currently dry Sebkha El-Melah lake in western Algeria is occasionally filled with water, shedding light on the extreme storm events required to sustain such bodies of water.
Key Findings
- Between 2000 and 2021, hundreds of powerful rainstorms were recorded in the lake’s drainage basin, yet only six instances led to substantial lake-filling events.
- These lake-filling events were driven by precipitation systems originating from the Atlantic Ocean, rather than equatorial sources as previously believed.
- The moisture transport process involves the interaction of extratropical cyclones near the North African Atlantic coast with upper-level atmospheric patterns, creating conditions favorable for heavy precipitation events.
- A crucial factor in these events is the recycling-domino effect, in which moisture is progressively transported and enhanced over the Sahara before reaching the lake’s drainage basin.
- The stationarity of weather systems, lasting typically three days, contributes significantly to the occurrence of lake-filling events.
This research challenges conventional theories suggesting that prehistoric lakes in the Sahara were primarily filled by monsoonal rains from the south. Instead, it highlights the role of Atlantic-origin storms, which deliver oceanic moisture into the desert, bypassing the Atlas Mountains. These findings have important implications for understanding past climate conditions and predicting future hydrological changes in desert environments.
The study further suggests that potential future climate shifts—driven by global warming—have the potential to fill Saharan lakes not only due to increased rainfall, but also because of changes in the frequency of extreme rainstorms. This could reshape water availability in the region, with significant consequences for ecosystems and human settlements.
By integrating climate science, meteorology, remote sensing, and hydrology, this research bridges a critical knowledge gap and provides a framework for future studies on Sahara Desert hydrology and climate dynamics.
Reference: “Meteorological ingredients of heavy precipitation and subsequent lake-filling episodes in the northwestern Sahara” by Joëlle C. Rieder, Franziska Aemisegger, Elad Dente and Moshe Armon, 17 March 2025, Hydrology and Earth System Sciences.
DOI: 10.5194/hess-29-1395-2025
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