Abstract
The El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) account for a large part of modern climate variability. Over the last decades, understanding of these modes of climate variability has increased but prediction in the context of global warming has proven difficult because of the lack of pertinent and reproducible paleodata. Here, we infer the dynamics of these oscillations from fossil assemblage and calcification state of coccolithophore in the Californian margin because El Niño has a strong impact on phytoplankton ecology and PDO on the upwelling intensity and hence on the ocean chemistry. Intense Californian upwelling brings water rich in CO2 and poor in carbonate ions and coccolithophores secrete lower calcified coccoliths. Seasonally laminated sediments of the Santa Barbara Basin are used to document ENSO variability and PDO index for the last 2700 years at a temporal resolution of 3 years. The records present the same characteristics as other PDO or ENSO records from the same area spanning the last centuries. We are therefore confident on the value produced here for the last 2.7 millennia. The records show important centennial variability that is equivalent to solar cycles.
Highlights
El Niño Southern Oscillation (ENSO) and its longer lived cousin, the Pacific Decadal Oscillation (PDO) (Zhang et al 1997), are the primary sources of global interannual variability
During the cold phases of ENSO or PDO (La Niña or negative PDO), the Aleutian Low (AL) is centered over the northwest Pacific and the North Pacific High (NPH) intensifies leading to strengthening of the California Current (CC), associated upwelling, and a weakening of Davidson Current (DC)
A Coccolithophore markers of ENSO The high-resolution record of the coccolith assemblages present in core BASIN04 and covering the last 100 years (Grelaud et al 2009b) indicates that higher relative abundances of G. oceanica are associated with El Niño years (Fig. 3)
Summary
El Niño Southern Oscillation (ENSO) and its longer lived cousin, the Pacific Decadal Oscillation (PDO) (Zhang et al 1997), are the primary sources of global interannual variability. Located in the center of the California Current System (CCS), the SBB is seasonally affected by two opposite currents: the southward California Current (CC) during late spring and summer; and the northward Davidson Current (DC, known as the California Countercurrent or the California Undercurrent) during late fall and winter. The intensity of these two currents is modulated by the North Pacific High (NPH) and the Aleutian Low (AL). ENSO and PDO are modulating the strength of the upwelling system in SBB
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