Drilling the crater Lake Challa near Mt. Kilimanjaro
Long continental climate records from tropical and sub-tropical regions are crucial to resolve long-standing questions about the relative importance of tropical and high-latitude climate processes in translating external climate forcing into regional climate variability. Available late-Quaternary lake and speleothem records show that on orbital time scales tropical monsoon rainfall mostly responded to precession-driven changes in low-latitude summer insolation. ICDP-drilled climate records also revealed the occurrence of African mega-droughts during the period of incipient glaciation (Marine Isotope Stage 5a-d), compared to which the iconic Last Glacial Maximum drought may have been modest, at least in certain parts of the continent. Despite these advances, a satisfactory mechanistic analysis of past climate change in the tropics remains hampered by the fragmentary nature and poor geographical coverage of available paleodata, and ambiguity about exactly which aspect of the tropical hydrological cycle (rainfall, moisture balance, magnitude of seasonal variability) is actually reflected in each of the many paleohydological proxies extracted from lake cores. What is missing in particular is a long continental climate record from near the equator, where twice-annual passage of the Intertropical Convergence Zone (ITCZ) creates the characteristically bimodal seasonal rainfall regime.
We propose ICDP drilling project ‘DeepCHALLA' to exploit the continuous sediment record of Lake Challa in easternmost equatorial Africa. Its principal objective is to acquire high-resolution and well-dated proxy data of continental climate and ecosystem change near the Equator, spanning a full glacial-interglacial cycle (150,000 years, covered by the uppermost ~100 m of Quaternary deposits). Easternmost equatorial Africa is perhaps the most appropriate region worldwide to pursue this record, because in this region seasonal ITCZ migration spans the widest latitude range, and hence tropical atmospheric dynamics associated with northern and southern monsoon systems most strongly interact. Located east of the Congo Air Boundary, the Challa climate record will also show limited overprint of glacial-interglacial variations in Atlantic thermohaline circulation, and thus most clearly reveal the signatures of truly equatorial climate processes. Available reflection-seismic data reveal a detailed record of past lake-level fluctuations over at least the last 150,000 years; and put the age of the volcanic caldera forming the Challa crater basin at ~250-300,000 years. Multiple-proxy analyses of the uppermost 22 meter of the sediment record through the ESF-EuroCLIMATE project CHALLACEA has already allowed calibration and validation of a wide range of proxies, producing a unique picture of climate and ecosystem change on the East African equator during the last 25,000 years.
(Figure: View across the lake to the Kibo and Mawenzi peaks of Mt. Kilimanjaro.)
Africa, Tanzania, Kenya, Kilimanjaro, Lake Challa
3° 19' S, 37° 42' E (Please scroll down to end of page for more information.)
Project Start and End
- workshop March 4 to 9, 2012
- Dirk Verschuren, University of Ghent, Department of Biology, Limnology Unit
- Marc De Batist, University of Ghent, Department of Geology and Soil Science, Renard Centre of Marine Geology
- Jaap S. Sinninghe Damste, Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry
- Bas van Geel, University of Amsterdam, Institute for Biodiversity and Ecosystem Dynamics
- Johannes (Hans) van der Plicht, University of Groningen, Centre for Isotope Research
- Gerald H. Haug, Max-Planck-Institute Mainz for Chemistry, Department of Climate Geochemistry
- Daniel Joseph Conley, University of Lund, GeoBiosphere Science Centre, Quaternary Sciences
- Philip A. Barker, University of Lancaster, Department of Geography, The Lancaster Environment Center
- Maarten Blaauw, Queen's University Belfast, School of Geography, Archeology and Paleoecology, The Chrono Center
- Fengsheng Hu, University of Illinois, Department of Plant Biology
- James Michael Russell, Brown University, Department of Earth, Environmental, and Planetary Sciences
- Mathias Vuille, State University of New York, University at Albany, Department of Atmospheric and Environmental Sciences
- Alan L. Deino, Berkeley Geochronology Center
Africa, CHALLA, DeepCHALLA, Dynamics, ICDP-2011/13, Kenya, Kilimanjaro, Lake Challa, Monsoons, Paleoclimate, Tanzania, Tropical Climate
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