Changes in Deep Water Oxygenation of the South China Sea Since the Last Glacial Period

Abstract

The Pacific meridional overturning circulation is thought to have a significant influence on global climate. However, the extent to which intermediate and deep circulations have changed in the Pacific Ocean since the Last Glacial Maximum (LGM) is not well known. At present, the South China Sea Deep Water (SCSDW) is fed by the upper Pacific Deep Water. Here we present new benthic foraminiferal δ13C and redox‐sensitive elemental data from a sediment core retrieved from the southern deep SCS to reconstruct the oxygenation history of the SCSDW since the LGM. Oxygenation records from the deep SCS and intermediate and deep waters in the Pacific Ocean demonstrate that the SCSDW deeper than 1,600 m has been sourced by the Pacific Deep Water since the LGM. Our data suggest that the well‐ventilated North Pacific Intermediate Water would not have influenced the SCSDW during cold stadials of the last deglacial period.

Photosynthetic Production Determines Bottom Water Oxygen Variations in the Upwelling Coastal South China Sea Over Recent Decades

“…Over the past few decades, an increasing number of DOrelated proxies based on biomarkers, elements (i.e., molybdenum and uranium), and foraminifer (i.e., Bulimina marginata and Quinqueloculina spp.) have been proposed and applied to reconstruct paleo-DO or paleo-redox conditions (e.g., Nakakuni et al, 2017;Nakakuni et al, 2018;Li et al, 2018;Naafs et al, 2019;Jacobel et al, 2020;Wakeham, 2020, and references therein). Among the biomarker-derived redox proxies, the 5α-stanol/Δ 5 -sterol ratios are widely used because eukaryotederived Δ 5 -sterols are ubiquitous in aquatic environments and can be anaerobically transformed to 5α-stanol counterparts without aerobic re-conversion (e.g., Gaskell and Eglinton, 1975;Wakeham, 1989;Wakeham, 2020;Berndmeyer et al, 2014;Nakakuni et al, 2017Nakakuni et al, , 2018.…”

Contrasting Sensitivity of Weathering Proxies to Quaternary Climate and Sea‐Level Fluctuations on the Southern Slope of the South China Sea

“…Millennial‐scale oscillations in clay mineralogy driven by the EASM intensity are also present in our southern SCS record, but cannot be so clearly resolved because of its lower sedimentation rate (Figure 3h), while this variability is superimposed on a clear precessional signal. In general, a 23 Kyr periodicity in the smectite/(illite + chlorite) ratio (Figure 3h) in phase with precession‐driven insolation indicates that the response of clay mineralogy in the low‐latitude SCS to the prevailing EASM arises rapidly, presumably mainly through changing chemical weathering intensity (M. Li, Ouyang, et al., 2018; S. Zhao et al., 2018).…”

Interactions Between Depositional Regime and Climate Proxies in the Northern South China Sea Since the Last Glacial Maximum

“…The oceanographic connection between the North Pacific and the SCS makes this marginal sea an ideal location in which to reconstruct the past evolution of North Pacific Intermediate Water (NPIW) and to assess any links with millennial‐scale climate variability during the last deglaciation (∼19–11 ka) (K.‐F. Huang et al., 2013; G. Li et al., 2018a). During the last deglaciation, major meltwater discharges reduced North Atlantic surface water density and may have weakened the Atlantic meridional overturning circulation (AMOC) during HS1 and perhaps the Younger Dryas (YD) (McManus et al., 2004).…”

“…Cold intervals are the Younger Dryas (YD) and Heinrich Stadial 1 (HS1) (blue-gray), and the Last Glacial Maximum (LGM; gray). links with millennial-scale climate variability during the last deglaciation (∼19-11 ka) (K.-F. Huang et al, 2013;G. Li et al, 2018a).…”