EGU2020-5888, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-5888
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Linking Paleo Vegetation Modelling with a Phytolith Record for the African Humid Period (15 - 5 ka BP) of the Omo-River-Lowlands and the Chew Bahir Basin, southern Ethiopia

Markus Lothar Fischer1,2, Fabian Sittaro3, Claudia Manntschke1, Chad Yost4, Verena E Foerster5, Frank Schäbitz5, Christian Schepers5, Martin H Trauth6, and Annett Junginger1,2
Markus Lothar Fischer et al.
  • 1Department of Geosciences, Eberhard Karls University Tuebingen, Hoelderlinstr. 12, 72074 Tuebingen, Germany
  • 2Senckenberg Centre for Human Evolution and Paleoenvironment (S-HEP), Sigwartstr. 10, 72076 Tuebingen, Germany
  • 3Institute of Geography, University of Leipzig, Johannisallee 19a, 04103 Leipzig, Germany
  • 4Department of Geosciences, University of Arizona, 1040 E 4th St, Tucson, AZ 85721, United States
  • 5Faculty of Mathematics and Natural Sciences, University of Cologne, Gronewaldstr. 2, 50931 Cologne, Germany
  • 6Institute of Geoscience, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany

Modern-day southern Ethiopia exhibits a complex mosaic of vegetation types. These types range from desert scrubland along the shores of Lake Turkana, to woodlands and wooded grasslands in the Omo-River-Lowlands and Chew Bahir catchment, and Afromontane forests of the Ethiopian Highlands. Over the past 20 ka, this region has experienced a variable climate, from the dry Last Glacial Maximum (25-18 ka BP) to the wet African Humid Period (15-5 ka BP), and back to present-day dry conditions. These oscillations likely had an impact on the biosphere and its human inhabitants. The biosphere, especially climate-induced changes in vegetation, in turn have a feedback effect on the local climate – and must therefore be considered in climate models and hydro-balance models. However, there are hardly any data on changes in vegetation during the dry-humid-dry transition of the AHP that could be used to parameterize such models.

As a contribution to an enhanced understanding of the role that paleo-vegetation could have played during those transitions, we present here a new comprehensive vegetation model. This study links a Predictive Vegetation Model (PVM) with the available vegetation-proxy records from southern Ethiopia, including a new phytolith record from Chew Bahir. The PVM uses an 18-year averaged time series of the Global Precipitation Measurement as well as SRTM elevation data to predict an 18-year averaged time series of MODIS landcover and vegetation parameters using boosted regression trees. We linked the PVM and resulting surface parameters (moisture availability, surface drag coefficient, albedo) with an existing hydro-balance model of the southern Ethiopian Rift to calculate precipitation during the AHP and hence also model the paleo-vegetation during this period. Available paleo-vegetation data including a new grass phytolith record from the sediments of an 11 m-meter long sediment core from the margin of paleo-Lake Chew Bahir were then used to compare model and proxy results. Being able to validate our new model data with actual vegetation proxy data for the first time enables us to gain valuable insights into the paleo-dimension of the vegetation mosaic of southern Ethiopia, a possible habitat of early Homo sapiens.

How to cite: Fischer, M. L., Sittaro, F., Manntschke, C., Yost, C., Foerster, V. E., Schäbitz, F., Schepers, C., Trauth, M. H., and Junginger, A.: Linking Paleo Vegetation Modelling with a Phytolith Record for the African Humid Period (15 - 5 ka BP) of the Omo-River-Lowlands and the Chew Bahir Basin, southern Ethiopia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5888, https://doi.org/10.5194/egusphere-egu2020-5888, 2020

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