From extreme rainfall to drought: 250 years of annually resolved sediment deposition in Santa Barbara Basin, California

Abstract

The Mediterranean climate of southern California is marked by droughts and extreme precipitation events. Here we use elemental variations generated by scanning X-ray fluorescence (XRF) to identify droughts and floods in recently deposited (1755–2008) sediments of Santa Barbara Basin (SBB) from box core SPR0901-04BC. The first principal component (PC1) of the scanning XRF elements has high loadings for elements associated with the lithogenic component of SBB laminae couplets, while the second (PC2) is associated with biogenic components. We interpret PC1 as a proxy for river runoff and PC2 as a proxy for marine productivity. High values of PC1 are associated with El Niño events and positive (warm) phases of the Pacific Decadal Oscillation (PDO), while low values of PC2 are associated with El Niño events and negative (cool) phases of the PDO. Droughts such as the 1934–40, 1949–56, and 1989–91 events coincide with low PC1 values. In addition to distinguishing interannual and decadal variability in the elemental composition of SBB sediments, several historic floods can be recognized including a gray flood layer associated with the 1861–62 flood, and a peak in PC1 associated with the flood following the St. Francis Dam disaster in 1928.