HR: 0800h
AN: PP41A-0183    [Abstracts]
TI: Ecological Change in Arctic Lakes: the Limitation of the Palaeolimnological Record
AU: * Anderson, N J
EM: gynja@lboro.ac.uk
AF: Loughborough University, Department of Geography, Loughborough, LE11 3TU, United Kingdom
AB: The evidence for ecological change in arctic lakes is now unambiguous and is considered to have started about 1850 and to be driven by increases in air temperature. In the context of longer-term, regional changes, however, this summary overlooks a three important factors: dating control of the recent sediments can be problematical, spatial heterogeneity of lake responses at the landscape scale is often ignored and finally, other possible drivers exhibit similar trends to that of air temperature, most notably atmospheric pollutants. 210-Pb together with 14-C are widely used to date lake sediment records but are often problematical because of the low sedimentation rates. In particular, in the arctic 210-Pb provides a chronology covering less than 100 years, often with large uncertainties. Importantly, biological change often predates reliable 210-Pb data. Arctic lake districts often contain thousands of lakes, possibly with considerable among lake variability in terms of their response to external drivers. The density of palaeolimnological sampling is often too low to support regional upscaling. Finally, environmental change in the arctic is driven by more than just increases in air temperature. Arctic environments are far from pristine and have been subjected to long-range atmospheric pollution (e.g. Pb, Hg and N) for long- periods: the effects of these other drivers are often ignored, possibly because they are difficult to separate from temperature trends. Deriving independent palaeo-proxies for the drivers of environmental change is problematical because of poor understanding of the controlling biogeochemical and ecological processes. The implications of these factors for understanding ecological change over the last 2000 years are discussed using examples from lakes in SW Greenland, an area with over 20,000 lakes and a range of water chemistries.
DE: 1621 Cryospheric change (0776)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4950 Paleoecology
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting