High-resolution interannual precipitation reconstruction of Southern California: Implications for Holocene ENSO evolution

Abstract

The variability of El Niño-Southern Oscillation (ENSO) on centennial to millennial time-scales is poorly understood due to the insufficient length, continuity, or resolution of existing paleoclimate records. Here we present a new, continuous, sub-annually resolved scanning XRF Ti record from marine sediments collected from Santa Barbara Basin (SBB) to reveal interannual precipitation changes in Southern California for the past 9000 yrs. Interannual precipitation variability in Southern California is closely related to ENSO through an atmospheric teleconnection with the tropical Pacific. Thus, Southern California precipitation reconstructions provide an opportunity to explore ENSO variability through time. Wavelet analysis of the SBB Ti record demonstrates interannual (2–7 yrs) precipitation variance was relatively weak prior to 4.4 ka, and significantly increased after 4.4 ka. Our record demonstrates a relationship between Southern California precipitation and the tropical Pacific and extratropical climate. The inferred increase of ENSO variability during the late Holocene is generally consistent with the published tropical Pacific ENSO records, and could be associated with a southward shift of the Intertropical Convergence Zone (ITCZ). Meanwhile, a deeper, westward-shifted Aleutian Low after 4.4 ka may have strengthened the ENSO teleconnection between the tropical Pacific and Southern California, contributing to the amplified interannual precipitation variance in the SBB record. Community Earth System Model (CESM) simulations through the Holocene (0, 3, 6, 9 ka) support the role of both the ITCZ and the AL in the enhancement of interannual precipitation variability in Southern California.