High Resolution, Absolute Dated Terrestrial Climate Record of Temperature and Precipitation From the Eastern US Covering 0-7ka, 116-127ka, and 145-298 ka

Analysis of 4 stalagmites from Buckeye Creek Cave (BCC) in West Virginia provides a high resolution record of temperature and precipitation in the eastern US. Periods of coverage include 0-7ka, 116-127ka, and 145-298 ka. Samples were dated using U/Th dating techniques developed for carbonates (Broecker 1963) and adapted for measurement on mass spectrometer (Edwards et al., 1987). The chronology is constrained by 6-14 dates per sample. Replication is the best method to ensure that observed isotopic changes are due to regional climate and not kinetic fractionation or heterogeneous behavior within the cave environment. When replication is available within the BCC record, there is general agreement in the timing, direction, and magnitude of shifts in δ13C and δ18O. Such agreement supports the interpretation of the isotopic composition of speleothem calcite as a climate signal. The δ18O record can reflect either temperature or precipitation. Since the record contains glacial and interglacial intervals and has a range of 2‰ (~5.5 °C at +0.35‰/°C), it is reasonable to conclude that temperature effects determine the isotopic composition of the samples. However, temperature cannot explain the entire record, as Marine Isotope Stages (MIS) 1 and 5e demonstrate more negative values than during full glacial conditions (MIS 6 & 8). Therefore precipitation must be a contributing factor. Such an interpretation is supported by the δ13C record. During arid periods, rock-water interaction time is increased, leading to a positive shift in δ13C (Denniston et al., 2007). Our record is ~4‰ higher during glacial periods than during MIS 1 and 5e. Broadly speaking, our record tracks insolation. However, one remarkable aspect of this record is the behavior of δ18O at insolation peaks. Our record contains four abrupt negative shifts in δ18O during maxima in local summer insolation greater than 520 W/m2. Temperature change does not provide a compelling explanation for this behavior as it would require ~3°C cooling during a period of maximum summer insolation. Therefore, we interpret these rapid shifts as the onset of enhanced precipitation due to an increase in precipitable moisture associated with warmer temperatures or a change in atmospheric circulation. References: W.S. Broecker, Journal of Geophysical Research 68, 2817-2834 (1963). R.L. Edwards et al., Earth and Planetary Science Letters 81, 175-192 (1987). R. Denniston et al., Quaternary Research 68, 45-52 (2007).