10,000 YEARS OF HYDROLOGIC VARIABILITY IN NORTHERN CALIFORNIA USING SEDIMENT FROM NORTH YOLLA BOLLY LAKE, CA

California faces a perennial water availability crisis. Key to understanding this crisis is a paleo perspective. Here, we examine sediment cores collected from North Yolla Bolly Lake (NYBL) to infer Holocene hydrologic variability of the Northern Coast Range of California. At 40°N latitude, the lake is located at the approximate average latitude of the California precipitation dipole (Dipole), which is the leading control of winter precipitation spatial variability in California. Thus, our site is critically located to examine how the Dipole has changed in the past. To examine Holocene hydrologic variability for NYBL, a multi-proxy methodology was followed. The methods included: cm-scale magnetic susceptibility, cm-scale organic and carbonate content, cm-scale grain size determination, 2 cm-scale C(org): N(total) ratios, and cm-scale XRF elemental analyses. Age control is based on AMS dates (n = 15) taken from macroscopic organics. Based on statistical analysis, we divide the Holocene into five hydrologic stages with drier conditions in the early Holocene, 10.0 - 8.85 ka, followed by a long period of wetter winters between 8.85 - 2.85 ka before declining rapidly between 2.85 and 2.0 ka. The latter drier period is contemporary to the Late Holocene Dry Period recognized throughout the Great Basin and California. Notably, this dry period corresponds to more frequent La Niña-like conditions. A comparison to insolation and various Pacific-sourced ocean-atmosphere forcings (e.g., El Niño - Southern Oscillation, sea surface temperatures) to the entire NYBL record reveals a dynamic winter hydroclimatic response, expressing non-stationary behavior, where the relationship between ENSO, for example, and winter wetness changes through time. This non-stationarity fits with NYBL’s location at the heart of the Dipole where modern interannual precipitation varies the most.