Relationship between annual precipitation variability and ENSO in Southern California for the past 9,000 years

The El Niño-Southern Oscillation (ENSO) has a major influence on Southern California's hydroclimate. The field correlation analysis of historical observational data (reanalysis data from 1901 to 2013 C.E.) and model simulations (e.g. CESM-CAM5 Last Millennium Ensemble) demonstrates that the interannual (with a 2-7 year periodicity) precipitation variability in Southern California is closely related to ENSO. The Santa Barbara Basin (SBB), offshore Southern California preserves a unique annually laminated marine sedimentary archive of modern and Holocene hydroclimate variability. Here we present sub-annually (4-7 samples per year) resolved scanning XRF Ti from deep sea cores SPR0901-03KC (34˚16.914' N, 120˚ 02.419'W; 591 m water depth) and MV0811-14JC (34˚16.906'N, 120˚02.162'W; 580 m water depth) collected from SBB to reconstruct an annual precipitation record for the past 9,000 years. Titanium (associated with silicate minerals) is delivered to SBB sediments by river runoff, which in the Mediterranean climate of Southern California occurs after winter season precipitation. High Ti counts, accompanied by more frequent floods (identified as gray clay layers) coincide with wet intervals identified in Southern Californian lacustrine records between 400-800, 3000-5500, 6600-7300 and 8500-9000 years BP. Interannual precipitation variance in the 2-7 year ENSO band was determined using wavelet analysis. The amplitude of ENSO band precipitation variance in SBB was generally low prior to 5000 years BP, with the exception of intervals between 6100-6600 and 8500-8900 years BP. The amplitude of ENSO band variability increased after 4500 years BP, accompanied by the appearance of longer period (5-7 years) ENSO band variance while shorter period (2-3 years), low-amplitude ENSO band variance characterized the SBB hydroclimate record prior to 5000 years BP.