A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia

Research output: Contribution to journalResearch articleContributedpeer-review



Eastern Africa has experienced strong climatic changes since the last deglaciation (15g000 years ago). The driving mechanisms and teleconnections of these spatially complex climate variations are yet not fully understood. Although previous studies on lake systems have enhanced our knowledge of Holocene precipitation variation in eastern Africa, relatively few studies have reconstructed the terrestrial temperature history of eastern Africa from lake archives. Here, we present (i) a new branched glycerol dialkyl glycerol tetraether (brGDGT) temperature calibration that includes Bale Mountains surface sediments and (ii) a quantitative record of mean annual air temperature (MAT) over the past 12gkagcalgBP using brGDGTs in a sediment core collected from Garba Guracha (3950gmga.s.l.) in the Bale Mountains. After adding Bale Mountains surface sediment (nCombining double low line11) data (Baxter et al., 2019) to the existing East African lake dataset, additional variation in 6-methyl brGDGTs was observed, which necessitated modifying the MBT5ME′ calibration (MBT denotes methylation of branched tetraethers) by adding 6-methyl brGDGT IIIa′ (resulting in the MBT Bale Mountains index, r2Combining double low line0.93, p<0.05). Comparing the MBT5ME′ and the new MBT Bale Mountains index, our high-altitude Garba Guracha temperature record shows that warming occurred shortly after the Holocene onset when the temperature increased by more than 3.0gg-C in less than 600 years. The highest temperatures prevailed between 9 and 6gkacalBP, followed by a temperature decrease until 1.4gkacalBP. The reconstructed temperature history is linked to supraregional climatic changes associated with insolation forcing and the African Humid Period (AHP), as well as with local anomalies associated with catchment deglaciation and hydrology.


Original languageEnglish
Pages (from-to)5357-5374
Number of pages18
Issue number23
Publication statusPublished - 30 Nov 2022