Stormy Rains in the Sahara Offer Clues to Past and Future Climate Changes
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Stormy Rains in the Sahara Offer Clues to Past and Future Climate Changes


New research reveals that heavy precipitation sourced from the Atlantic ocean, are the primary drivers of present-day lake filling in the northwestern Sahara. The study finds that only the most intense and prolonged precipitation events trigger lake-filling episodes, challenging long-standing assumptions about past climate conditions in the region. These findings suggest that projections of enhanced rainfall intensity and frequency in the Sahara could potentially reshape water availability in the desert.

A new study supervised by Dr. Moshe Armon from the Institute of Earth Sciences at Hebrew University and Dr. Franziska Aemisegger from University of Bern, in collaboration with Dr. Elad Dente from University of Haifa, led by their student Joëlle Rieder at ETH Zurich, recently published in Hydrology and Earth System Sciences, provides new insights into the meteorological processes responsible for the filling of a normally dry lake in the northwestern Sahara. The research offers a fresh perspective on past climate variations and suggests we can learn from past flooding of the lake on ongoing climate change and future water resources in the desert.

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.
The research paper titled “Meteorological ingredients of heavy precipitation and subsequent lake-filling episodes in the northwestern Sahara” is now available in Hydrology and Earth System Sciences and can be accessed at https://hess.copernicus.org/articles/29/1395/2025/
DOI 10.5194/hess-29-1395-2025
Researchers:
Joëlle C. Rieder1, Franziska Aemisegger1,2,3, Elad Dente4,5, and Moshe Armon1,6
Institutions:
1. Institute for Atmospheric and Climate Science, ETH Zurich
2. Institute of Geography, University of Bern
3. Oeschger Centre for Climate Change Research, University of Bern
4. Department of Geology and Environmental Science, University of Pittsburgh
5. School of Environmental Sciences, University of Haifa
6. The Fredy and Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem
Archivos adjuntos
  • Rare Flooding of Sebkha el Melah: Atlantic Moisture Drives Unusual Precipitation in the Northwestern Sahara (September 2024) | Credit: Moshe Armon | Caption: The normally dry northwestern Sahara lake, Sebkha el Melah, was filled for the seventh time since the beginning of the 21st century. This flood, in September 2024, which occurred after the study was conducted, happened because of heavy precipitation in the Sahara associated with the same atmospheric patterns described in the paper, in which Atlantic moisture is driven far into the desert. Landsat 9 imagery is from the NASA Worldview application (https://worldview.earthdata.nasa.gov), part of the NASA Earth Science Data and Information System (ESDIS).
Regions: Middle East, Israel, Africa, Algeria
Keywords: Science, Climate change, Earth Sciences, Environment - science

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