Author ORCID Identifier

Date of Award


Degree Type


Degree Name

Master of Science (MS)



First Advisor

Daniel Gebregiorgis, PhD

Second Advisor

Crawford Elliott, PhD

Third Advisor

Lawrence Kiage, PhD


The δ18O ratio in speleothems is a proxy for many different climate variables. Here, we present δ18O reconstructions at sub-annual resolution timescales spanning the early-Holocene period (i.e., 9.03 to 8.84 ka) from a speleothem sample collected from a cave site located within the core sink region of the East African monsoon (EAM). The δ18O time series documents persistent decadal and interdecadal scale variability throughout the growth period, spanning the classic El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) bandwidths (i.e., 2–7 years). The observed variability in the stalagmite δ18O time series suggests that the Eastern African monsoon system is regulated by the ENSO and the Indian Ocean Dipole (IOD), similar to the present-day conditions. The observed range of δ18O values is larger than any inter-annual and decadal variation observed in the modern-time reconstructions from the same cave, indicating increased East African monsoon variability than it observed today. However, further investigation should investigate whether monsoon intensity changes or other factors exclusively govern the observed δ18O variability.


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