Terrigenous material supply to the Peruvian central continental shelf (Pisco, 14° S) during the last 1000 years: paleoclimatic implications

Abstract

Abstract. In the eastern Pacific, lithogenic input to the ocean responds to variations in the atmospheric and oceanic system and their teleconnections over different timescales. Atmospheric (e.g., wind fields), hydrological (e.g., fresh water plumes) and oceanic (e.g., currents) conditions determine the transport mode and the amount of lithogenic material transported from the continent to the continental shelf. Here, we present the grain size distribution of a composite record of two laminated sediment cores retrieved from the Peruvian continental shelf that record the last ∼ 1000 years at a sub-decadal to centennial time-series resolution. We propose novel grain size indicators of wind intensity and fluvial input that allow reconstructing the oceanic–atmospheric variability modulated by sub-decadal to centennial changes in climatic conditions. Four grain size modes were identified. Two are linked to aeolian inputs (M3: ∼ 54; M4: ∼ 91 µm on average), the third is interpreted as a marker of sediment discharge (M2: ∼ 10 µm on average), and the last is without an associated origin (M1: ∼ 3 µm). The coarsest components (M3 and M4) dominated during the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP) periods, suggesting that aeolian transport increased as a consequence of surface wind stress intensification. In contrast, M2 displays an opposite behavior, exhibiting an increase in fluvial terrigenous input during the Little Ice Age (LIA) in response to more humid conditions associated with El Niño-like conditions. Comparison with other South American paleoclimate records indicates that the observed changes are driven by interactions between meridional displacement of the Intertropical Convergence Zone (ITCZ), the South Pacific Subtropical High (SPSH) and Walker circulation at decadal and centennial timescales.

Multidecadal Changes in Marine Subsurface Oxygenation Off Central Peru During the Last ca. 170 Years

“…The presence of diatom bands in B-13 and B-14 in this period (not visible in B-6 because of a hiatus; Salvatteci et al, 2014a) and peaks of biogenic silica content indicate that massive algal blooms were frequent. Algal blooms in this period might be enhanced by a prevailing water column stratification, inferred from the warm sea surface temperatures (Gutiérrez et al, 2011) and weak surface winds (Briceño Zuluaga et al, 2016). The second time period was represented by a (multi)decadal oscillation of the WCD and organic input (co-variation of B. seminuda and B. tenuata) and a sustained relaxation of reducing conditions to non-sulfidic sediments off Callao and Pisco (Figure 6).…”

“…Our goal is to determine the relative importance of largescale (i.e., ocean-atmosphere) versus local processes (i.e., export production) driving sub-surface oxygenation off Peru. To do so, we compared our results to other geochemical proxies analyzed in the same box cores (described in detail in Sifeddine et al, 2008;Gutiérrez et al, 2009Gutiérrez et al, , 2011Salvatteci et al, 2014bSalvatteci et al, , 2016Briceño Zuluaga et al, 2016) and to regional paleo-records.…”

Deglacial to Holocene Ocean Temperatures in the Humboldt Current System as Indicated by Alkenone Paleothermometry

“…Data of sea-level pressure and wind stress for the last decades suggest an overall trend toward a stronger, La Niña-like Walker Circulation (England et al, 2014;L'Heureux et al, 2013). While during the Mid-Holocene, the productivity was low in the HCS perhaps due to the upwelling of subsurface waters containing low nutrients; the last century is characterized by high marine productivity (Gutierrez et al, 2011;Salvatteci et al, 2018) likely due to a favorable combination of a strong and nutrient-rich oxygen minimum zone (Salvatteci, Gutierrez, et al, 2014), high summer-spring water column stratification (Salvatteci et al, 2018), and strong winds (Briceño-Zuluaga et al, 2016). While the present study provides important insight in the context of climate change, the impact of future global warming on the biological productivity in the HCS remains uncertain and should be treated as such in future management strategies (Salvatteci et al, 2018).…”

Latitudinal variations in <i>δ</i><sup>30</sup>Si and <i>δ</i><sup>15</sup>N signatures along the Peruvian shelf: quantifying the effects of nutrient utilization versus denitrification over the past 600 years

“…Along the Peruvian margin the main source for the high amounts of upwelled nutrients (30 µmol L −1 for both Si(OH) 4 and NO − 3 ; Bruland et al, 2005) is the subsurface Peru-Chile Undercurrent (PCUC), which flows southward along the continental slope and outer shelf between 4 and 14 • S at a depth between 50 and 150 m, before it detaches from the shelf south of 15 • S (Brink et al, 1983;Chaigneau et al, 2013;Toggweiler et al, 1991). Eastwardflowing subsurface waters of the Equatorial Undercurrent (EUC) and the Southern Subsurface Counter Current (SSCC) (see Fig.…”