A MULTI-PROXY RECONSTRUCTION OF HYDROCLIMATE VARIABILITY IN THE SOUTHWESTERN NORTH AMERICA OVER THE LAST MILLENNIUM

To better understand the natural range and the mechanisms leading to past hydrologic variability in southwestern North America (SWNA), we are using the stable isotope and trace element data of speleothem from Crystal Cave in Sequoia National Park, California, on the south-western flank of the Sierra Nevada Mountains (36.59 °N; 118.82 °W; 1386 m) from 854 to 2007 AD. Precipitation variability in this region has been attributed to sea surface temperature (SST) regimes in the Pacific and Atlantic Oceans and to the attendant shifts in atmospheric circulation patterns. We recently found that a positive correlation between the oxygen isotopes of the Crystal Cave speleothem and the SST in the Kuroshio extension region of the northwest Pacific can explain 52% of the variance and interpret this record as a reconstruction of SST anomalies in the Kuroshio extension region. A comparison with tree-ring records of precipitation located near the study site shows that some droughts in this region occurred during periods of warmth in the Kuroshio extension region, similar to the instrumental record. However, other droughts did not and instead must have been influenced by other factors. Combining multiple proxies is a powerful tool to reconstruct paleoenvironmental conditions. Here we investigate and report the results of carbon isotope and trace element variations in the Crystal Cave speleothem to provide more information about hydroclimate conditions in SWNA over the last millennium.