Although there is growing evidence on the warming of the California Current and its effects on an observed declining zooplankton biomass for the last four decades we still lack of long enough records that will allow us to discern between a proposed anthropogenic climate warming and the North Pacific's characteristic oceanographic and climatic variability on interannual to decadal time-scales. Here we will present results derived from a high resolution reconstruction of sea surface properties from the southern part of the California Current with the goal of characterizing the strength and variability of its flow on longer timescales than the existing instrumental record that will enable us to recover the interannual to secular periodicities that modulate its physical and biogeochemical variability.
For this reconstruction we use several cores of laminated sediments retrieved from a silled basin, known as Cuenca San Lazaro, in the southern Baja California continental margin located at 25N with a sea-floor depth of 540 m bathed by suboxic waters of the North Pacific. Our study site is further characterized by relatively high levels of primary production, mostly a consequence of the advection of the cold and nutrient rich California Current waters and associated upwelling processes, which are responsible for the production and high export of organic matter, opaline and calcitic shells to the sea-floor, the origin of the light lamina in the cores of this basin. The preserved microfaunal and geochemical indices record the variations in the strength of the cooler flow of the California Current.
We will present results of our calibration on the variability of the abundance and composition of planktic foraminifera, its stable isotopic records on sea surface variability, and the alkenone derived paleotemperature record for the last II centuries for this southernmost region of the California Current. We we will extend our reconstruction to periods prior to the instrumental records that will allow us to recover the physical and biological variability and dominant periodicities for this interesting dynamic boundary between the northern relatively colder and fresh waters of the California Current and the warmer more saline tropical waters from the south.