CALIFORNIA HYDROCLIMATE VARIABILITY SINCE THE LAST GLACIAL MAXIMUM: PRELIMINARY STALAGMITE RESULTS FROM CRYSTAL CAVE, SEQUOIA NATIONAL PARK, CA

Speleothem and Lake records from Southwestern North America have revealed substantial interannual to orbital-scale variations in temperature, precipitation, and ecosystems during the last deglaciation and Holocene. These variations have been linked to both external forcing and internal climate variability driven by Earth’s orbital variations, the strength of Atlantic meridional overturning circulation (AMOC), the size of Northern Hemisphere ice sheets, Pacific sea surface temperature patterns, and related changes in atmospheric circulation. However, the relative importance of these factors in California remains unclear, due to the limited availability of continuous paleoclimate archives spanning the Late Pleistocene and Holocene. To address this, we have developed a new U-Th dated speleothem stable isotope (δ¹⁸O and δ¹³C) from Crystal Cave in Sequoia National Park. Our decadal-resolution record spans the last ~21 kyr, and shows evidence for a cold-wet Heinrich Stadial 1 and Younger Dryas, and a warm-dry Bølling-Allerød. Oxygen isotopes show muted evidence for orbital-scale changes in temperature and storm trajectories during the Holocene, but stable carbon isotopes suggest a drying trend since ~7 kyr BP, potentially in response to declining Northern Hemisphere summer insolation.