Multidecadal climate variability in the southern region of the California Current System during the last 1800 years

How climate warming is going to affect the multidecadal climate variability in the North Pacific remains an open question. Here we present a record of this type of variability inferred from carbon productivity and sea surface temperature (SST) proxies in high-resolution sediment records from the Southern California Current System (CCS). The reconstruction covers ~1,800 years of the Common Era and is associated with the latitudinal migration of the CCS tropical boundary at multidecadal timescales. Inorganic carbon proxies and a Globigerinoides ruber Mg/Ca summer SST reconstruction are associated with the intrusion of the tropical waters in the Southern CCS and organic carbon proxies with the strength of the California Current (CC). From these and other sediment components, we derived a principal component that captures the balance between tropical and subarctic waters in the study region. This principal component record shows further connections with land moisture records, which suggests a link with Pacific basin scale climate reorganization. The results show periods of reduced Pacific multidecadal climate variability associated with cold periods in the Northern Hemisphere (NH). We propose a mechanism related with the southward migration of the westerlies during relatively cool periods in the NH and a southward shift of the North Pacific Current, which could have reduced the advection of subarctic waters to the subtropical region.