Relationships between the Tropical Pacific and the Southern California Current productivity at different timescales

The influence of Tropical Pacific in climate during the Common Era has been largely debated due to the lack of agreement between proxies. Some records suggest a La Niña-like conditions during the Medieval Climate Anomaly (MCA) and El Niño-like conditions during the Little Ice Age (LIA) (i.e. Graham et al., 2007), but other records suggest the contrary (i.e. Conroy et al., 2008). Here we present a 2.3Ky biogenic based record from San Lázaro Basin that, in its different modes of variability, contains both visions. Furthermore, these proxies share a centennial mode of variability that dominates the last millennium and connects the Indo-Pacific Warm Pool (IPWP) with the Western North America Drought Area Index (WNA-DAI) through variations in the thermocline.

San Lázaro Basin (SLB) is a suboxic basin located in the southern dynamic boundary of the California Current System (CCS). During La Niña-like conditions, the intensification of the trade winds increase the Ekman transport and the invasion of subartic waters, with the result of a shoaled thermocline and enhanced ecosystem productivity. When the winds relax, El Niño-like conditions became, and the intrusion of warm stratified water from the tropical and subtropical regions plummeted the productivity and a coccolitophorid based ecosystem dominates. The opposite relation between Carbonates and Total Organic Carbon (TOC) in SLB sediments confirms this observations. A significant positive correlation between XRF measurements of Br/Si with TOC and Ca counts with Carbonates, allows us to study SCC variability from interannual to centennial resolution.

The Spectral Analysis of Br/Si and Carbonates show a common ~110y cycle that is also present in the IPWP and WNA-DAI with a ENSO-like pattern. This centennial mode is excited by warm Equatorial Pacific conditions as its variance is correlated with Galapagos precipitation record. Although Galapagos precipitation record has been related with ENSO intensity, the Br/Si interannual variability coincides with the ENSO reconstructions that suggest increased El Niño events during the LIA. We will discuss the implications of this double relationship with ENSO proxies and the links between our proxies and other paleorecords in the Pacific.