On October 24, 2024, an extratropical cyclone dramatically altered the arid landscape of the Sahara Desert, creating ephemeral lakes following intense rainfall that delivered the equivalent of a year's worth of precipitation in Morocco, Algeria, Tunisia, and Libya within just a few days. Notably, the Sebkha el Melah lake in Algeria emerged, showcasing a landscape reminiscent of a much greener and wetter past in this vast desert region.
Satellite images from NASA's Operational Land Imager-2 aboard Landsat 9 reveal a striking contrast between the lake's dry bed on August 12 and its filling on September 29. The lake covered 191 square kilometers with a depth of 2.2 meters, approximately 33% full, according to Moshe Armon, a researcher at the Hebrew University of Jerusalem who analyzed the satellite data.
Images from Landsat 9 and other satellites, including NASA's Terra, highlight changes not only in Sebkha el Melah but also in other ephemeral lakes near Erg Chebbi in Morocco, indicating how overflowing rivers from the Atlas Mountains contributed to this phenomenon, as reported by Live Science.
This rare and largely undocumented transient event has occurred only twice in Sebkha el Melah since 2000, with previous occurrences in 2008 and 2014. The phenomenon offers insights into the Sahara's climate thousands of years ago, during the African Humid Period, when the desert was significantly greener and wetter, supporting ancient human life.
Despite evidence suggesting a wetter past, there is ongoing scientific debate regarding the Sahara's historical humidity levels. Current climate models often fail to replicate the necessary precipitation levels to sustain the vast lakes believed to have existed. Events like the filling of Sebkha el Melah provide critical data for understanding these historical climates.
Dr. Moshe Armon posits that extreme rainfall events, such as those seen in September in northwest Sahara, may have been more frequent in the past. Given the slow drying process of these lakes, similar events could have kept them partially filled for years or decades, even with infrequent rainfall.
These findings are vital for understanding both the historical and future climate of the Sahara. While small orbital variations known as Milankovitch cycles were the primary drivers of the African Humid Period, current climate change adds complexity to these patterns.
Projections from the Intergovernmental Panel on Climate Change (IPCC) suggest that some areas of the Sahara may experience increased rainfall as global temperatures rise, while others could become even drier. However, uncertainties surrounding these projections remain significant, leaving the future of the Sahara unclear.