Deepwater circulation variation in the South China Sea since the Last Glacial Maximum

Zheng, Xiaoxu; Kao, Shuh Ji; Chen, Zhong; Menviel, Laurie; Chen, Han; Du, Yan; Wan, Shiming; Yan, Hong; Liu, Zhonghui; Zheng, Lei; Wang, Shuhong; Li, Dawei; Zhang, Xu

doi:10.1002/2016gl070342

Cited by 38 publications

(31 citation statements)

References 64 publications

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“…On the other hand, increased intermediate-water temperature in the subtropical Pacific recorded in core GH08-2004 (1166 m water depth) (Kubota et al, 2015) and young deep water observed in the northern South China Sea during HS1 (Wan and Jian, 2014) along the downstream region of the NPIW are also related to an intensified NPIW formation. Furthermore, the pathway of GNPIW from numerical model simulations (Zheng et al, 2016) was similar to modern observations (You, 2003). Thus, all of this evidence implies a persistent cause-andeffect relation between GNPIW ventilation, the intermediate and deep water oxygen concentration in the OT, and sediment redox state during HS1.…”

Section: Effects Of Gnpiw On Sedimentary Oxygenationsupporting

confidence: 71%

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

et al. 2020

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The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO 2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO 2 levels on millennial timescales is poorly constrained. An increase in the respired CO 2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. This link thus offers a chance to study oceanic ventilation and coeval export productivity based on redox-controlled sedimentary geochemical parameters. Here, we investigate a suite of geochemical proxies in a sediment core from the Okinawa Trough to understand sedimentary oxygenation variations in the subtropical North Pacific over the last 50 000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals and after 8.5 ka, while oxygenation decreased during the Bölling-Alleröd (B/A) and Preboreal. The enhanced oxygenation during cold spells is linked to the North Pacific Intermediate Water (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast trade winds over the tropics. The enhanced formation of the NPIW during Heinrich Stadial 1 (HS1) was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in the high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A due to a decreased NPIW formation and enhanced export production, indicates an expansion of the oxygen minimum zone in the North Pacific and enhanced CO 2 sequestration at mid-depth waters, along with the termination of atmospheric CO 2 concentration increase. We attribute the millennial-scale changes to an intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation.

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Section: Effects Of Gnpiw On Sedimentary Oxygenationsupporting

confidence: 71%

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

et al. 2020

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“…Similarities in physical and chemical properties of deep waters between the SCS and the Pacific at 2000 water depth (Chang et al, 2010;Wang et al, 2011;Wyrtki, 1961) reveal that the SCS deep water comes from the deep water of the open western Pacific, which is primarily originated from the Southern Ocean nowadays (Kawabe & Fujio, 2010). Proxies of deep water ventilation age (i.e., the difference between coexisted benthic and planktic 14 C age) (Wan & Jian, 2014), foraminiferal neodymium isotope (ENd) (Wu et al, 2015) and sedimentary magnetic properties (Zheng et al, 2016) in the SCS have been also used to reconstruct the history of the Pacific intermediate/deep circulation since the last glacial period. Therefore, the SCS offers a unique opportunity for understanding the deep circulation in the low-latitude western Pacific during the glacial cycle (Jian & Wang, 1997;Qu et al, 2006;Tian et al, 2006;Wan & Jian, 2014;Wu et al, 2015;Zheng et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Deep Hydrography of the South China Sea and Deep Water Circulation in the Pacific Since the Last Glacial Maximum

Wan

Jian

Dang

2018

Geochem Geophys Geosyst

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The oxygen (δ18O) and carbon (δ13C) isotopic compositions of benthic foraminifer Cibicidoides wuellerstorfi as reliable proxies of deep water properties were compiled from 50 core‐top and down‐core sites in the South China Sea (SCS) for two time slices of the late Holocene and Last Glacial Maximum (LGM) to reconstruct the glacial deep hydrographic structure. The bathymetric profiles of both δ18O and δ13C in the SCS show similar trends between the LGM and the late Holocene, but the δ18O gradients between intermediate (∼500–1,000 m) and deep (>1,500 m) waters obviously increased during the LGM, indicating an intensified bathyal stratification and weakened vertical mixing between intermediate and deep waters in the SCS during the glacial period. A spatial comparison of bathymetric δ18O and δ13C profiles was also made for the Southern Ocean (Indo‐Pacific sector) and southwest Pacific, western equatorial Pacific (i.e., Ontong Java Plateau), off‐Japan margin as well as the SCS. The meridional δ13C profiles indicate a decreasing trend of δ13C (“aging effect”) in the deep layer (∼1,200–2,600 m) from south to north, reflecting a northward flow pathway of deep waters from the southwest Pacific (upstream) to the low‐latitude northwest Pacific and the SCS (downstream) during the LGM. The gradients of deep water δ18O (∼1,200–2,600 m) between these upstream and downstream regions were higher during the LGM relative to the Holocene, implying that a greater contribution of the northern‐sourced North Pacific Intermediate Water (NPIW) with a relatively low δ18O signature to the deep waters in the low‐latitude Pacific during the LGM.

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“…L. Zhao et al, 2015, and references therein; Figure 1b). Previous studies of the SCS sediments have demonstrated that contour currents is strengthened during Heinrich stadials deduced from the striking increase of both magnetic susceptibility and mean size of sortable silt Zheng et al, 2016), coinciding with a period of the weakened East Asian summer monsoon (Sun et al, 2012;Y. J. Wang et al, 2001;Wen et al, 2016).…”

Section: Paleoceanography and Paleoclimatologymentioning

confidence: 92%

“…As an outcome of the North Pacific Deep Water intrusion to the SCS through Luzon Strait, the contour currents characterized by a tunnel-like vertical structure flow along the continental slope at water depth of around 1,650-2,000 m inferred from modern in situ observations (W. Zhao et al, 2014;Y. Previous studies of the SCS sediments have demonstrated that contour currents is strengthened during Heinrich stadials deduced from the striking increase of both magnetic susceptibility and mean size of sortable silt Zheng et al, 2016), coinciding with a period of the weakened East Asian summer monsoon (Sun et al, 2012;Y. Previous studies of the SCS sediments have demonstrated that contour currents is strengthened during Heinrich stadials deduced from the striking increase of both magnetic susceptibility and mean size of sortable silt Zheng et al, 2016), coinciding with a period of the weakened East Asian summer monsoon (Sun et al, 2012;Y.…”

Section: Paleoceanography and Paleoclimatologymentioning

confidence: 95%

Responses of the East Asian Summer Monsoon in the Low‐Latitude South China Sea to High‐Latitude Millennial‐Scale Climatic Changes During the Last Glaciation: Evidence From a High‐Resolution Clay Mineralogical Record

Zhao

Liu

Colin

et al. 2018

Paleoceanog and Paleoclimatol

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High‐resolution clay mineral assemblage combined with Nd and Sr isotopic compositions of Core MD12‐3434 located in the northern South China Sea was investigated to reveal terrigenous sediment response to the East Asian monsoon evolution during the last glaciation. Clay mineralogical variations indicate clear millennial‐scale oscillations that are mainly due to rapid changes in the proportion of smectite to illite and chlorite. Smectite is derived predominantly from rapid chemical weathering of volcanic rocks in Luzon under strong summer monsoon, while illite and chlorite are mainly sourced from Taiwan through reinforced physical erosion. Thus, the smectite/(illite + chlorite) ratio is adopted to reconstruct the East Asian summer monsoon evolution during the last glaciation. Rapid increases in the smectite/(illite + chlorite) ratio imply strengthened summer monsoon occurred during Dansgaard‐Oeschger and Bølling‐Allerød interstadials. In contrast, rapid decreases in the ratio indicate relatively weakened summer monsoon happened during Heinrich and Younger Dryas stadials. These millennial‐scale climatic signals documented by clay mineralogical compositions of deep‐sea sediments in the South China Sea can be better preserved in calm deeper‐water sedimentary environments. Our study highlights the prompt responses of the East Asian monsoon system to millennial‐scale climatic changes occurred in high‐latitude Northern Hemisphere through contemporaneous chemical weathering of volcanic rocks and/or sediment supply variations under strong physical erosion in the low‐latitude South China Sea, implying an atmospheric teleconnection from the North Atlantic to the Asian monsoon region.

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Deepwater circulation variation in the South China Sea since the Last Glacial Maximum

Cited by 38 publications

References 64 publications

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

Deep Hydrography of the South China Sea and Deep Water Circulation in the Pacific Since the Last Glacial Maximum

Responses of the East Asian Summer Monsoon in the Low‐Latitude South China Sea to High‐Latitude Millennial‐Scale Climatic Changes During the Last Glaciation: Evidence From a High‐Resolution Clay Mineralogical Record

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