HIGH-RESOLUTION RECORDS OF DEGLACIAL CLIMATE CHANGE FROM THE CENTRAL SIERRA NEVADA, CALIFORNIA

Two multi-proxy speleothem paleoclimate records with annual to decadal resolution from McLean’s Cave in the central Sierra Nevada foothills provide new insights into changes in California hydroclimate across glacial-interglacial transitions. Speleothem ML1 grew from ~19 to 12 ka across the MIS 2/1 boundary, and speleothem ML2 grew from ~ 67 to 55 ka across the MIS 4/3 boundary. U-series dating of the speleothems provides precise ages for climate perturbations in this region related to Heinrich Events 1 (16.5 to 15.7 ka) and 6 (61.1 to 59.8 ka). The records document shifts to colder and wetter conditions in eastern California during both Heinrich Events, signified by abrupt decreases in speleothem δ¹⁸O, δ¹³C, and Mg, Sr, and Ba concentrations. In contrast, during global interstadials, our stalagmite records are marked by increases in δ¹⁸O, δ¹³C, and trace element concentrations consistent with enhanced prior calcite precipitation and dolomite dissolution in the epikarst, which we attribute to warmer and drier conditions above the cave. Transitions to warmer and drier conditions in eastern California during growth of the ML1 and ML2 speleothems appear to precede shifts to interstadial conditions in the Greenland ice core record, a finding that is corroborated by other western North American speleothem records of Termination I. Spectral analysis of trace element records with multi-annual to sub-annual resolution from both stalagmites indicates a stronger presence of periodicities in the 3 to 8 year range during interstadials, suggesting an enhanced role for the El Niño Southern Oscillation in modulating precipitation in this region during warm periods.