Abrupt Climate Change During Marine Isotope Stage 3 in Southern Tropical Africa: Multiproxy Reconstructions from Lake Tanganyika

Brown University, Providence RI

Investigators

Abstract

Marine Isotope Stage 3 (MIS3), a period from ~30,000 to 60,000 years before present, is characterized by large, abrupt millennial-scale warmings recorded at numerous sites in the northern hemisphere. Records from Antarctica and the southern mid-latitudes suggest that the southern hemisphere cools when the North warms as part of a 'bipolar seesaw' in the oceans and atmosphere. However, there are virtually no records from the southern tropics or from tropical Africa to test the spatial extent of this pattern, despite the potential importance of the tropics in synchronizing, propagating, and triggering millennial-scale climate change. This grant will investigate MIS3 millennial-scale variability in southern tropical Africa using sediment cores from Lake Tanganyika. The project will apply sensitive new proxies including the del-D of fatty acids, the TEX86 paleothermometer, del-15N, del-13C, and % biogenic silica to reconstruct effective precipitation, temperature, and paleolimnologic variability in the lake within an chronologic framework based on accelerator mass spectrometry carbon-14 dating. This work will provide important insight into millennial-scale variability in the southern tropics, the mechanisms triggering and propagating abrupt climate changes, the evolution of "glacial aridity" in tropical Africa, and the controls on upwelling and productivity in Lake Tanganyika. Intellectual Merits: Understanding the spatial patterns of millennial-scale climate changes will yield information critical to understanding their underlying physics and mechanisms, and will provide fundamental data to test the ability of climate models to simulate abrupt climate change. The southern hemispheric tropics are crucial to interhemispheric heat and moisture transfer during abrupt climate changes, yet the southern tropics, and in particular tropical Africa, are poorly represented in the network of MIS3 records. Broader Impacts: This research will provide a new record of climate variability from a drought-prone, densely inhabited region whose climate history is poorly known. This study will promote multidisciplinary approaches to investigating paleoclimate, and will result in one graduate student dissertation and the training of undergraduate students in cross-disciplinary laboratory techniques. Lake Tanganyika is one of the most important lakes in Africa for studies of rift basin geology, lacustrine endemism, limnology, and paleoclimatology. This work will provide insight into the long-term controls on the lake's limnology and productivity, and will use innovative new tools to investigate the sedimentary record.