PP025-08
Climatic controls on the triple oxygen isotope composition of East African monsoon precipitation and implications for speleothem paleoclimate reconstructions
Thursday, 10 December 2020: 10:58
Virtual
Daniel Gebregiorgis1, Zelalem K Bedaso2, Kim M Cobb3, Daniel Deocampo4, Luke Pangle4 and Asfawossen Asrat5, (1)Georgia State University, Department of Geosciencese, Atlanta, GA, United States, (2)University of Dayton, Geology, Dayton, OH, United States, (3)Georgia Institute of Technology, Earth and Atmospheric Sciences, Atlanta, GA, United States, (4)Georgia State University, Department of Geosciences, Atlanta, GA, United States, (5)Addis Ababa University, School of Earth Sciences, Addis Ababa, Ethiopia
Abstract:
Future evolution of the East African monsoon under increasing atmospheric CO
2 levels is highly uncertain. This is partly due to a limited understanding of past monsoon variability inferred from traditional water isotope-based proxy records that dominate available climate archives (e.g. speleothems). Despite significant progress in precipitation isotope monitoring in eastern Africa, the
18O/
16O system hasn’t been fully constrained. The newly developed triple oxygen isotope (
17O/
16O,
18O/
16O) technique could provide additional information to distinguish different climatic factors and processes that influence isotopic fractionation in the water cycle and paleo-precipitation proxy records in speleothems. Understanding the spatial and temporal variability of precipitation isotopes, and their climatic controls, is critical to unlocking the potential of paleoclimate records from this region. We will present the first triple oxygen isotope data from daily-resolved precipitation samples collected from multiple stations across Northern, Central, and Southern Ethiopian highlands and investigate the sensitivity of
δ18O and
δ17O to changes in monsoon precipitation and their potential as regional paleoclimate proxies.
Our previous results from stations under the direct influence of the East African monsoon show that δ18O variations are poorly correlated to precipitation amount but show some correspondence to increased storm activity and deep convection (Bedaso et al., 2020). Triple oxygen isotope data of East African precipitation would provide additional constraints on the influence of evaporation, moisture source and convective processes in the hydrologic cycle. Ultimately, comparison between daily time series of triple oxygen isotopes from multiple stations, which are located in different climate regimes and physiographic regions at varying distance from coastlines, will allow us to examine the role of mesoscale and microscale convective processes on 17O-excess signature of monsoon precipitation. These datasets serve as a baseline for understanding cave proxy formation as we undertake reconstruction of Holocene monsoon history from newly collected speleothems from the Northwestern Ethiopian highlands.
References
Bedaso, Z. K., et al., 2020. Journal of Hydrology 585, p.124364.
