Climatic change in northern Ethiopia during the past 17,000 years: a diatom and stable isotope record from Lake Ashenge

Michael H. Marshall, Henry F. Lamb, Sarah J. Davies, Melanie J. Leng, Zelalem Kubsa, Mohammed Umer, Charlotte Bryant

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

Lake Ashenge, a closed-basin lake near the northernmost penetration of summer monsoon rains, is well placed to provide a continental record of past changes in the strength of the African monsoon system. Diatom and oxygen isotope analyses of the lake sediments confirm that the overall trend of climate change during the past 17,000 years was driven by precessional forcing, punctuated by abrupt shifts that may be linked to changes in Atlantic surface temperatures. The lake level was low from at least 17.2 to 16.2 cal kyr BP, and then rose between 16.2 and 15.2 cal kyr BP, which may represent a temporary reactivation of the monsoonal circulation system following its reduced activity during the Last Glacial Maximum. The lake was significantly low between 13.6 and ~ 11.8 cal kyr BP coinciding approximately with the Younger Dryas, but beginning 900 years before its recognised onset in the Greenland ice-core record. A major sedimentary hiatus, covering the interval ~ 11.8 to 7.6 cal kyr BP, was probably caused by an early Holocene lowstand, the precise timing of which cannot be determined because pre-lowstand sediments were eroded from the core site. The lake filled to its overflow from 7.6 cal kyr BP until 5.6 cal kyr BP, when the sediments record an abrupt lake response to the regional transition to arid conditions that mark the end of African Humid Period. Evidence is also presented for climate changes which may have been associated with the rise and fall of Aksum, Ethiopia's first great civilisation.
Original languageEnglish
Pages (from-to)114-127
Number of pages14
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume279
Issue number1-2
Early online date13 May 2009
DOIs
Publication statusPublished - 01 Aug 2009

Keywords

  • Diatoms
  • Stable isotopes
  • Lake level
  • Monsoon
  • Ethiopian highlands

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