HR: 11:50h
AN: GC32A-07    [Abstracts]
TI: Response of Rwenzori (Uganda - DR Congo) Glaciers and Mountain Lake Ecosystems to Climate Change: Past, Present, Future
AU: * Eggermont, H
EM: Hilde.Eggermont@ugent.be
AF: Limnology Unit, Department of Biology, Ghent University, K.L. Ledegancstraat 35, Ghent, 9000, Belgium
AU: Russell, J
EM: James_Russell@brown.edu
AF: Geological Sciences, Brown University, Box 1846, Providence, RI, 0912, United States
AU: Verschuren, D
EM: Dirk.Verschuren@ugent.be
AF: Limnology Unit, Department of Biology, Ghent University, K.L. Ledegancstraat 35, Ghent, 9000, Belgium
AB: Ice caps and glaciers in the mountains of tropical Africa are expected to disappear within two decades as a result of human-induced global warming. Loss of permanent ice from Africa's mountains will have profound effects on Afroalpine ecosystems, as well as the hydrology and temperature regime of Africa's unique, alpine cold-water lakes. Consequently, there is an urgent need to document the baseline climatic, environmental, and biological conditions in Africa's mountains against which to evaluate future changes. While climatic, limnological, and ecological monitoring can provide key insights into modern conditions, sediments accumulating on the bottom of alpine glacial lakes chronicle the history of central African climate and environmental dynamics, and can thus produce the historical perspective needed for resource conservation. In this context, over the course of three field expeditions (2005-2007) we surveyed virtually all lakes (19) on the Ugandan side of the Rwenzori Mountains, Uganda-Congo, to evaluate the sensitivity of these high-mountain lake ecosystems to climate change and glacier melting. We installed temperature and humidity loggers to monitor ongoing climate change, calibrated paleolimnological proxy indicators (sediment composition, organic carbon, biomarkers, aquatic biota) in surface sediments in relation to their present local lake environment, and analyzed gravity cores from selected lakes to document the history of recent glacier recession and ecosystem response. Here, we present an overview of the currently available climatic and environmental data sets, with a focus on sediment core data. Through comparison of the sedimentary history of glaciated and non-glaciated lake basins, we show that recent glacier recession started around 1880 AD, broadly coincident in timing with declining East African rainfall as documented by regional lake level datasets. However, our data do not suggest rapid glacial expansion coincident with the initiation of this wet phase in the early 19th century, highlighting the complexity of the relationship between tropical alpine glaciers and climate. Glacier recession starting at 1880 AD is accompanied by declining aquatic primary productivity, recorded in the isotopic composition of sedimentary organic matter. Together, our data show that Rwenzori's high-elevation lakes are responsive to alpine glaciation and constitute a unique laboratory to assess quantitatively the relationship between the extent of its glaciers, changes in central African climate, and ecosystem processes.
DE: 0720 Glaciers
DE: 1051 Sedimentary geochemistry
DE: 1630 Impacts of global change (1225)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting