Sensitivity of carbon paleoproductivity in the Southern California Current System on different time scales for the last 2 ka

Abstract

The San Lázaro Basin (SLB) sediment record is highly sensitive to the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) due to its location vertically underlying the dynamic boundary between the northern, cooler and fresher waters of the California Current System (CCS) and the southern, warmer and saltier surface waters from the subtropics and tropics. Warm sea surface temperatures (SSTs) and the ensuing stratified surface water column favor carbonate productivity, mostly dominated by the export of coccolithophorids as observed during El Niño events, while cool SSTs and a less stratified water column favor a relatively higher export of organic carbon. Here we show how during the last two millennia, the mechanisms that drive the organic carbon and carbonate export depend on the time scale considered. The organic carbon and carbonate records show opposite trends for the past 2000 years. On multicentennial periodicities, their variability is probably a result of precessional forcing and associated decreasing Northern Hemisphere insolation, which has been shown to affect the migration of the Intertropical Convergence Zone and the polar jet stream. On shorter time scales, interannual to centennial, the SLB records exhibit an ENSO-like variability; similarly, decadal to multidecadal variability is correlated with instrumental and reconstructed PDO records. We further show how interannual variance seems to have increased during the Little Ice Age, most likely related to large ENSO events, in contrast with an apparent reduction in this type of variability between 400 and 1350 Common Era, suggesting a changing sensitivity of the ENSO teleconnection in the southern CCS for the past two millennia. ABELLA-GUTIÉRREZ AND HERGUERA CARBON PALEOPRODUCTIVITY IN THE SOUTHERN CCS 953PUBLICATIONS Paleoceanography

Multidecadal Climate Variability in the Southern Region of the California Current System During the Last 1,800 Years

“…Although for the purpose of this study we would be able to construct an age model without considering the CH94‐2K core, we preferred to consider the additional four AMS 14 C determinations on this core for a better dating of the PCM00‐78K core base. The updated correlation between box and kasten cores further suggested a change in the reservoir age previously considered (Abella‐Gutiérrez & Herguera, —Figure S3). Here we use a reservoir age of 750 years to match the derived chronology from excess 210 Pb age estimates with the radiocarbon ones, instead of the 650 years of reservoir age used by Abella‐Gutiérrez and Herguera ()—Figure S3).…”

“…The updated correlation between box and kasten cores further suggested a change in the reservoir age previously considered (Abella‐Gutiérrez & Herguera, —Figure S3). Here we use a reservoir age of 750 years to match the derived chronology from excess 210 Pb age estimates with the radiocarbon ones, instead of the 650 years of reservoir age used by Abella‐Gutiérrez and Herguera ()—Figure S3). This older reservoir is still within the error considered by the Calib Reservoir Age tool.…”

“…Previous analysis showed coherence between inorganic and organic carbon proxies for periodicities below ~150 years, and their variance have been related with Pacific internal variability (Abella‐Gutiérrez & Herguera, ). To improve the understanding of the Pacific multidecadal variability in the Southern CCS, we first removed the multicentennial variability from the paleoproductivity (carbonate, Ca, C org , Br/Si, Br) and lithogenic (Fe, Ti, K, Si) proxies with the aid of singular spectrum analysis (SSA), considering a window length below N/3 (N being the number of samples).…”

“…We considered Si, K, Fe, and Ti XRF counts to evaluate the role of dilution by the terrigenous component. In addition, we include Br counts to separate from Si counts as Br/Si shows the best correlation with C org (see Abella‐Gutiérrez & Herguera, , for a detailed description of the methodology).…”

“…In a previous study, we have shown how the balance between inorganic and organic carbon exported to the seafloor in San Lazaro Basin is operating on multidecadal time scales (Abella‐Gutiérrez & Herguera, ). To understand this balance, we focused on the multidecadal variability of a two millennia long record of carbon productivity from San Lazaro Basin and a four centuries long summer SST reconstruction from Globigerinoides ruber (white) Mg/Ca measurements from the same core.…”