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THE CAPE BOUNTY INTEGRATED PALEOCLIMATE EXPERIMENT: CALIBRATING THE SEDIMENTARY AND SUBFOSSIL RECORD CONTAINED IN VARVES
LAMOUREUX, SCOTT F Queen's University.
Cockburn, Jaclyn M.H. Queen's University.
Stewart, Kailey A. Queen's University.
Forbes, Andrew C. Queen's University.
Francus, Pierre INRS-ETE, St. Foy.
A comprehensive watershed and lake monitoring program was initiated during the 2003 season at Cape Bounty, Melville Island, Nunavut (75dN, 108dW) to develop a field observation database for calibrating the paleoenvironmental record contained in varved sediments. The goal of the project is to collect hydrometeorological and limnological data for a six-year period at the site, to identify the key controls over inter- and intra-seasonal sediment delivery deposition in response to snow melt and summer rainfall events. A key element of the experimental design is the parallel study of two adjacent lakes with similar watershed conditions (bedrock, Quaternary deposits, relief, aspect, weather and vegetation) to determine the reproducibility of the varve record and to systematically identify signal and noise components. Additionally, the formation of the subfossil diatom record and related biogeochemical fluxes will be evaluated to identify the linkages between terrestrial and aquatic systems. The long term data derived from this work will be used to identify the comparative role of winter snow water equivalence (SWE) and melt season thermal conditions in the formation of varves. Previous research based on varve records has indicated both factors potentially act as primary controls over runoff and sediment delivery, but few studies have evaluated SWE directly.
The experimental design includes the following elements: a network of meteorological stations in both catchments, river stations for gauging and characterization of the suspended sediment load, and lake stations with traps and sensor arrays to measure deposition rates, bottom currents and sediment texture. Regular sampling of the rivers for particle size analysis will complement in situ measurement of particle size in the lake. Further analysis of the sedimentary environment will be carried out with a network of cores and acoustic characterization of the sedimentary fill in the lakes. Analysis of sediment cores will combine detailed microscopy and image analysis to determine sediment texture, mass accumulation rates, and composition to identify subannual sedimentary events of different origin.
Results from the first season of work indicate notable differences in SWE in the catchments that generated differences in the timing of sediment delivery between the two study watersheds. Despite these differences, both watersheds exhibit comparable responses to short-term hydrometeorological conditions, particularly rainfall events. For 2004, the sampling program will be substantially expanded to increase sample and trap recovery frequency.
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