Preprints
https://doi.org/10.5194/egusphere-2024-310
https://doi.org/10.5194/egusphere-2024-310
05 Mar 2024
 | 05 Mar 2024
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Fifty-year seasonal variability of East African droughts and floods recorded in Central Afar lake sediments (Ethiopia) and their connections with ENSO

Carlo Mologni, Marie Revel, Eric Chaumillon, Emmanuel Malet, Thibault Coulombier, Pierre Sabatier, Pierre Brigode, Hervé Gwenael, Anne-Lise Develle, Laure Schenini, Medhi Messous, Gourguen Davtian, Alain Carré, Delphine Bosch, Natacha Volto, Clément Ménard, Lamya Khalidi, and Fabien Arnaud

Abstract. Understanding past and present hydro-system feedbacks to global ocean-atmospheric interactions represents one of the main challenges to preventing droughts, extreme events and related human catastrophes in the face of global warming, especially in arid and semiarid environments. In eastern Africa, the El Niño-Southern Oscillation (ENSO) was identified as one of the primary drivers of precipitation variability affecting water availability. However, the northern East African Rift System (EARS) still suffers from ENSO climate teleconnection and the underrepresentation of predictive models because of the scarcity of local-to-regional historical or palaeo-data.

In this paper, we provide a 50-year seasonal flood/drought chronicle of the Awash River catchment from the study of laminated sediment from Gemeri and Afambo lakes (Central Afar region, Ethiopia), with the aim of reconstructing the magnitude of regional hydro-climatic events. Pluri-centimetric micro-laminated lithogenic facies alternating with pluri-millimetric carbonate-enriched facies are investigated in both lakes. We couple dating methods including radiocarbon, short-lived radionuclides, palaeomagnetic field variations and varve counting on both lake deposits to build a high-resolution age model and to discuss the regional hydro-sedimentary dynamics of the Awash River over the last ~700 years, with a focus on the last fifty years.

Using a multiproxy approach, we observe that following a multi-centennial enhanced hydrological period, the two lakes experienced a gradual decrease in river load inflow since 1979 CE, attaining extreme drought and high evaporative conditions between 1991 and 1997 CE. In 2014, the construction of a dam and the improvement of agricultural hydraulic management in the lower Awash River plain impacted the erodibility of local soils and the hydro-sedimentary balance of the lake basins, as evidenced by a disproportionate sediment accumulation rate.

Comparison of our quantitative reconstruction with i) lake water surface evolution expressed in Km2, ii) the interannual Awash River flow rates expressed in mm/yr, and iii) the El Niño 3.4 model highlights the intermittent connections between ENSO SST anomalies, regional droughts and hydrological conditions in the northern EARS.

Carlo Mologni, Marie Revel, Eric Chaumillon, Emmanuel Malet, Thibault Coulombier, Pierre Sabatier, Pierre Brigode, Hervé Gwenael, Anne-Lise Develle, Laure Schenini, Medhi Messous, Gourguen Davtian, Alain Carré, Delphine Bosch, Natacha Volto, Clément Ménard, Lamya Khalidi, and Fabien Arnaud

Status: open (until 30 Apr 2024)

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  • RC1: 'Comment on egusphere-2024-310', Anonymous Referee #1, 02 Apr 2024 reply
  • RC2: 'Comment on egusphere-2024-310', Anonymous Referee #2, 05 Apr 2024 reply
Carlo Mologni, Marie Revel, Eric Chaumillon, Emmanuel Malet, Thibault Coulombier, Pierre Sabatier, Pierre Brigode, Hervé Gwenael, Anne-Lise Develle, Laure Schenini, Medhi Messous, Gourguen Davtian, Alain Carré, Delphine Bosch, Natacha Volto, Clément Ménard, Lamya Khalidi, and Fabien Arnaud
Carlo Mologni, Marie Revel, Eric Chaumillon, Emmanuel Malet, Thibault Coulombier, Pierre Sabatier, Pierre Brigode, Hervé Gwenael, Anne-Lise Develle, Laure Schenini, Medhi Messous, Gourguen Davtian, Alain Carré, Delphine Bosch, Natacha Volto, Clément Ménard, Lamya Khalidi, and Fabien Arnaud

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Short summary
The reactivity of local to regional hydrology and soil to global changes remains understated in East African climatic models. This paper demonstrates the importance of studies on regional hydro-systems feedbacks to global atmospheric anomalies, to better understand and mitigate the sometimes catastrophic effects of global warming in extreme environments such as the Afar, especially in the context of current climate-induced food insecurity in East Africa and dire predictions for what is ahead.