NOAA/WDS Paleoclimatology - Bison Lake, Colorado Holocene Calcite Oxygen Isotope Data

A context for recent hydroclimatic extremes and variability is provided by a ~10 k.y. sediment carbonate oxygen isotope (d18O) record at 5-100 yr resolution from Bison Lake, 3255m above sea level, in northwestern Colorado (United States). Winter precipitation is the primary water source for the alpine headwater lake in the Upper Colorado River Basin and lake water d18O measurements reflect seasonal variations in precipitation d18O. Holocene lake water d18O variations are inferred from endogenic sedimentary calcite d18O based on comparisons with historic watershed discharge records and tree-ring reconstructions. Drought periods (i.e., drier winters and/or a more rain-dominated seasonal precipitation balance) generally correspond with higher calcite d18O values, and vice-versa. Early to middle Holocene d18O values are higher, implying a rain-dominated seasonal precipitation balance. Lower, more variable d18O values after ca. 3500 yr ago indicate a snow-dominated but more seasonally variable precipitation balance. The middle to late Holocene d18O record corresponds with records of El Niño Southern Oscillation intensification that supports a teleconnection between Rocky Mountain climate and North Pacific sea-surface temperatures at decade to century time scales.