Stalagmite evidence for Early Holocene multidecadal hydroclimate variability in Ethiopia

Asfawossen Asrat, Andy Baker, Wuhui Duan, Melanie J. Leng, Ian Boomer, Rabeya Akter, Gregoire Mariethoz, Lewis Adler, Catherine N. Jex, Meklit Yadeta, Lisheng Wang

Publikation: Bidrag til tidsskriftArtikelForskningpeer review

Abstrakt

A multiproxy oxygen and carbon isotope (δ13C and δ18O), growth rate, and trace element stalagmite paleoenvironmental record is presented for the Early Holocene from Ethiopia. The annually laminated stalagmite grew from 10.6 to 10.4 ka and from 9.7 to 9.0 ka with a short hiatus at ∼9.25 ka. Statistically significant and coherent spectral frequencies in δ13C and δ18O are observed at 15-25 and 19-23 years, respectively. The observed ∼1‰ amplitude variability in stalagmite δ18O is likely forced by nonequilibrium deposition, due to kinetic effects during the progressive degassing of CO2 from the water film during stalagmite formation. These frequencies are similar to the periodicity reported for other Holocene stalagmite records from Ethiopia, suggesting that multidecadal variability in stalagmite δ18O is typical. Several processes can lead to this multidecadal variability and operate in different directions. A hydroclimate forcing is likely the primary control on the extent of the partial evaporation of soil and shallow epikarst water and associated isotopic fractionation. The resulting oxygen isotope composition of percolation water is subsequently modulated by karst hydrology. Further isotopic fractionation is possible in-cave during nonequilibrium stalagmite deposition. Combined with possible recharge biases in drip-water δ18O, these processes can generate multidecadal δ18O variability.

OriginalsprogEngelsk
Sider (fra-til)67-81
Antal sider15
TidsskriftQuaternary Research
Vol/bind110
DOI
StatusUdgivet - 27 nov. 2022

Programområde

  • Programområde 5: Natur og klima

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