Documenting the spatial and temporal patterns of Holocene drought variability provides a means to place the current metrological trends in a longer perspective, and ultimately, to decipher the causes of regional-scale changes in the hydrologic cycle. One method to assess how drought frequency and duration has changed through time is to use oxygen and carbon isotope studies on authigenic carbonate preserved in laminated lake sediments. The authigenic carbonate is precipitated from the water column effectively archiving the oxygen isotope ratio of the lake water at the time of formation. This method works well in watersheds that are responsive to changes in the precipitation/evaporation balance (P/E), such as the Scout lake catchment discussed here.

Scout Lake is a small (<1 km2), shallow (7-m deep) closed-basin lake with limited surface inflow in the southwestern Yukon Territory, Canada. The lake basin is perched above the regional groundwater table making it sensitive to changes in P/E. The modern surface waters have high D and ¹⁸O values with respect to spring waters sampled in the watershed and the regional meteoric waterline suggesting that the lake is sensitive to the effects of evaporation. Scout Lake contains ~5 m of Holocene sediment banded at cm-scale. Here we focus on the upper 2 m that represents the last 4,000 years. The chronology of the late Holocene Scout Lake core is based on the White River Tephra (1150 BP) and 6 radiocarbon dates on charcoal. Results of oxygen and carbon stable isotope measurements indicate considerable P/E variability during the past 4,000 years with a marked trend toward higher δ¹⁸O values in the last several hundred years. The results track the general trend identified by previous lake-level and stable isotope studies in the region, but have considerably better temporal resolution averaging 6.5 years per sample.