CGRG Bibliography of Canadian Geomorphology
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Author : Anderson, L.; Abbott, M.B.; Finney, B.P.; and Edwards, M.E.
Date : 2000.
Title : Modern surface water isotope ratios: relationships and Inferences for lake sediment core d18 o paleoclimate reconstructions
Publication : 30th International Arctic Workshop, Program and Abstracts, 2000. Institute of Arctic and Alpine Research, University of Colorado at Boulder
Issue :
Page(s) : 8-9.
Abstract
The challenge for utilizing proxies of lake-water d 18 O for paleoclimatological and paleohydrological studies, such as authigenic calcite in lake-sediment cores, is to correctly infer the driving mechanisms for d 18 O variability for individual lakes. Previous work and experience has indicated that the guiding principle for evaluating controls on lake-water d 18 O is individual lake site hydrology and climatology (Anderson et al., in review; VonGrafenstein et al., 1999; Ricketts and Anderson, 1998; Talbot, 1990) Interpretations are based upon the estimated evaporation to input (E:I) ratios; lake-water d 18 O from lakes with high E:I ratios is thought to be primarily driven by evaporation, and lake-water d 18 O from lakes with a low E:I ratio is controlled by the d 18 O composition of input waters. However, only a few studies have explored this relationship with a statistically significant number of lake sites or measurements (Abbott et al., in review; VonGrafenstein and Erlenkeuser 1999; Sauer 1997). Here we explore relationships between lake-watershed characteristics and the isotopic composition of modern water samples from 25 closed and open lake basins, rivers, springs, groundwater and precipitation from the central Yukon Territory. The primary objective of this research is to empirically establish the paleohydrological interpretive framework of sediment-core authigenic calcite d 18 O stratigraphies from closed basin lakes in this region. The sampled lake sites include a wide range of hydrologic characteristics. Larger lakes are up to 40 km2 and small ponds are ~0.2 km2 . Watershed areas also range from large (up to 350 km2 ) to very small (~0.2 km2). Water budgets range from closed basins, to high volume overflowing lakes. Spring, groundwater, rivers and precipitation are found to plot on or very near the Global Meteoric Water Line (GMWL) while significant isotopic modification occurs (~12â 18 O-enrichment) within closed basin lake sites due to the preferential evaporation of the lighter 16 O-isotope. Relationships between d 18 O, d2H, lake area, lake depth, watershed area, elevation, inflow from precipitation, and estimated E:I are evaluated for the hydrological type associated with ranges of isotopic composition. These hydrologic types are proposed as a ëcalibrationí or analogue tool for interpreting sediment core d 18 O changes and the inferred paleohydrology. These results will clarify and empirically validate estimates of past moisture balance changes in the upper reaches of the Yukon River watershed.
Bibliography of Canadian Geomorphology