A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia
Eastern Africa has experienced strong climatic changes since the last deglaciation (15 000 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 Holoc...
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Published in | Biogeosciences Vol. 19; no. 23; pp. 5357 - 5374 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Katlenburg-Lindau
Copernicus GmbH
30.11.2022
Copernicus Publications |
Subjects | |
Online Access | Get full text |
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Summary: | Eastern Africa has experienced strong climatic changes since the
last deglaciation (15 000 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 12 ka cal BP using brGDGTs in a sediment core collected from Garba Guracha (3950 m a.s.l.) in the Bale Mountains. After adding Bale Mountains surface sediment
(n=11) 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, r2=0.93, 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 3.0 ∘C
in less than 600 years. The highest temperatures prevailed between 9 and 6 ka cal BP, followed by a temperature decrease until 1.4 ka cal BP. 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. |
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ISSN: | 1726-4189 1726-4170 1726-4189 |
DOI: | 10.5194/bg-19-5357-2022 |