Enhanced deepwater circulation and shift of sedimentary organic matter oxidation pathway in the Okinawa Trough since the Holocene

Kao, Shuh‐Ji; Horng, C. S.; Hsu, Shih-Chieh; Wei, Kuo-Yen; Chen, J.; Lin, Yu-Ju

doi:10.1029/2005gl023139

Cited by 44 publications

(55 citation statements)

References 32 publications

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“…1b). A similar trend in TS content (in terms of age) was found in core MD012403 in the southern OT (not shown) despite a ∼4 times higher sedimentation rate (Kao et al, 2005). This indicates that bottom water circulation change was a trough-wide phenomenon.…”

Section: Local Environmental Variation or Signal From Etnp?supporting

confidence: 57%

“…Total organic carbon content (TOC) and total sulfur content (TS, in lower time resolution) for both cores have been reported previously (Kao et al, 2005(Kao et al, , 2006b. Following their method for TS, we obtained a higher resolution TS record in this study.…”

Section: Study Areamentioning

confidence: 57%

“…More information on the age model including the AMS data can be found in Chang et al (2008b). Details of age model and related information for MD012403 have been reported in Kao et al (2005).…”

Section: Study Areamentioning

confidence: 99%

“…2a) might also significantly affect KC volumetric transport, surface and bottom circulations in the OT. Hydrological changes and subsequent effects on the sedimentary sulfur, organic carbon biogeochemistry (Kao et al, 2005(Kao et al, , 2006a and water column nutrient dynamics are discussed below. (Bassinot et al, 2002).…”

Section: Study Areamentioning

confidence: 99%

“…However, changes in local environmental conditions, which have been quite large, might also contribute to δ 15 N variation in the past 25 kyr (e.g., Kao et al, 2005Kao et al, , 2006a. The past environmental variation can be constructed from geochemical properties of the sediment core.…”

Section: Local Environmental Variation or Signal From Etnp?mentioning

confidence: 99%

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North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

et al. 2008

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Abstract. Sedimentary δ 15 N records in two IMAGES cores (MD012404 and MD012403) retrieved from the Okinawa Trough (OT) in the western North Pacific reveal deglacial increases with two peaks occurring during the Bølling/Allerød and the Preboreal/early Holocene periods. These peaks are synchronous with previously reported δ 15 N peaks in the Eastern Tropical North Pacific, although the amplitudes (from 3.8 to 5.8‰) are much smaller in the OT. Similar δ 15 N values for the last glacial maximum and the late-Holocene observed by us at a site far from the present-day zones of water-column denitrification (WCD) indicate that the mean 15 N/ 14 N of nitrate in the upper ocean did not differ much between the two climate states. The accumulation rate of organic carbon and total sulfur content are used as indices of the local WCD potential. The results suggest that enhancement of global WCD rather than local denitrification should be responsible for the deglacial maxima of sedimentary δ 15 N in the Okinawa Trough. Our data could provide additional constraints to better understand changes in nitrogen budget during the glacial to interglacial transition.

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Section: Local Environmental Variation or Signal From Etnp?supporting

confidence: 57%

Section: Study Areamentioning

confidence: 57%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Local Environmental Variation or Signal From Etnp?mentioning

confidence: 99%

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North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

et al. 2008

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New evidence for Kuroshio inflow and deepwater circulation in the Okinawa Trough, East China Sea: Sedimentary mercury variations over the last 20 kyr

Lim

Kim

et al. 2017

Paleoceanography

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The evolution of the Kuroshio Current (KC) in the Okinawa Trough (OT) has long been of paleoceanographic interest and has been the focus of many investigations because of its large impacts on both the ocean environment and the climate in East Asia. Here we present a new high‐resolution mercury (Hg) record from the OT sediments that provides robust evidence for the glacial‐interglacial variabilities of KC inflow. The Hg levels are anomalously high in the Holocene deposits, which feature a large and abrupt Hg increase at ~9.6 ka and a significant drop at 4.5–3.2 ka. Our observations show that most Hg was derived from seafloor hydrothermal plumes via active lateral transportation. Thus, the generally high Hg levels since ~9.6 ka are associated with enhanced basin‐wide deepwater circulation triggered by the KC inflow. This driving mechanism for the deposition and widespread of Hg is also evidenced by an abrupt drop in Hg levels during the late Holocene neoglacial cold period (~5–3 ka) when the KC inflow was temporarily interrupted and deepwater circulation was consequently weak or even absent in the OT. The changes in sedimentary Hg appear to be synchronous with those in other geochemical proxies that suggest that bottom water conditions switched from anoxic to oxic due to increased upwelling from the bottom in tandem with the strengthening KC and reduced freshwater effect since ~9.6 ka. This study shows that the hydrothermal Hg is a sensitive and independent tool for the reconstruction of paleodynamics of KC in the OT.

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Linkages between East China Sea Deep-sea Oxygenation and the Variability of the East Asian Summer Monsoon and Kuroshio Current over last 400,000 years

Vats

Singh

Das

et al. 2021

Preprint

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The East China Sea (ECS) seasonally receives a high organic input due to the terrestrial organic matter influx, which is controlled by the East Asian Summer Monsoon (EASM), and the increased productivity driven by upwelling of the subsurface Kuroshio Current (KC). Changes in benthic foraminiferal assemblage composition in combination with paleoceanographic proxy data (CaCO3 (%), TOC (%), δ 13 Cpf, and δ 18 Obf) are used to reconstruct bottom water oxygenation and organic export flux variability over the last 400 kyr in the ECS. Multivariate analyses of benthic foraminiferal census data identified six biofacies characteristic of varying environmental conditions. These results suggest that enhanced EASM precipitation and KC upwelling directly influenced organic export flux and bottom water oxygen content in the ECS. The ECS bottom water was suboxic during Marine Isotope Stage (MIS) 11 to 8; suboxic to dysoxic between MIS 7 and 6, strongly dysoxic between mid-MIS 5 and 4, and exhibited high variability between MIS 3 and 1. Spectral analysis of relative abundances of representative genera Quinqueloculina (oxic), Bulimina (suboxic), and Globobulimina (dysoxic) reveals a robust 23 kyr signal, which we attribute to precessionally-paced changes in surface productivity and bottom water oxygenation related to KC variability over the past 400 kyr.

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Enhanced deepwater circulation and shift of sedimentary organic matter oxidation pathway in the Okinawa Trough since the Holocene

Cited by 44 publications

References 32 publications

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

New evidence for Kuroshio inflow and deepwater circulation in the Okinawa Trough, East China Sea: Sedimentary mercury variations over the last 20 kyr

Linkages between East China Sea Deep-sea Oxygenation and the Variability of the East Asian Summer Monsoon and Kuroshio Current over last 400,000 years

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