Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North Pacific

Ding, Ling; Ge, Tiantian; Gao, Huiwang; Luo, Chunle; Xue, Yuejun; Druffel, Ellen R. M.; Wang, Xuchen

doi:10.1017/rdc.2017.143

Cited by 12 publications

(23 citation statements)

References 44 publications

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“…The Keeling plot of DIC is linear and possessed a high coefficient with R 2 = 0.66 ( p < 0.001, n = 63), as determined by Model II regression (geometric mean regression) (Figure a), confirming that the main controls on the observed distributions of DIC and Δ 14 C‐DIC were hydrodynamic mixing processes within the SCS. The DIC Keeling plot in the SCS (slope = 3.5 × 10 6 ) is consistent with those obtained in the Kuroshio Extension region and the eastern NP (4 × 10 6 and 4.29 × 10 6 , respectively), confirming that DIC concentrations and Δ 14 C‐DIC can be used as conservative tracers of water mass movement and water parcel homogenization (Beaupré & Aluwihare, ; Ding et al, ), and thus the distribution of Δ 14 C‐DIC could be predicted by the solution mixing model in the SCS. If we use the average value of 49‰ for Δ 14 C‐DIC of the Kuroshio water mass in the upper 500 m depth (Stations C05 and C08) and −218‰ for Δ 14 C‐DIC of the NP deep water at depths deeper than 1,500 m (Figure a and Table S2), we calculated that 46–82% of the NP deep water could have been upwelled and mixed with Kuroshio water in the upper 250–700 m depth based on the mass balance, thus resulting in the observed Δ 14 C‐DIC profiles in the SCS, suggesting that water mixing in the upper 800 m depth in the basin of the SCS is quite dynamic and the ventilation by water exchange is more rapid in the upper 800 m depth than that in the deep basin water.…”

Section: Discussionsupporting

confidence: 83%

“…The Δ 14 C‐DIC and DIC concentrations have been used as conservative tracers of water mass movement and water parcel homogenization in the ocean (Beaupré & Aluwihare, ; Ding et al, ; Key et al, ). The majority of DIC in the surface ocean (0–100 m) is from atmospheric CO 2 entering the ocean through air‐sea exchange and dissolved as carbonate species.…”

Section: Discussionmentioning

confidence: 99%

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Radiocarbon in Dissolved Organic and Inorganic Carbon of the South China Sea

Ding

Shan

et al. 2020

JGR Oceans

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We present the carbon isotope ( 14 C and 13 C), dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC) concentration measurements in the South China Sea (SCS) to reveal the different sources and cycling time scales of the two major carbon pools in the SCS. The DIC concentrations ranged from 1,776 to 2,328 μmol kg −1 , and they were lower at the surface and increased with depth. Conversely, the DOC concentrations ranged from 38 to 95 μM, and they were higher on the surface and decreased rapidly in the upper 500-m water depth. The DIC Δ 14 C and DOC Δ 14 C values varied from −227‰ to 68‰ and −557‰ to −258‰, respectively, and both decreased with depth until 1,500 m and then remained relatively constant. DOC Δ 14 C values were −330‰ lower than DIC Δ 14 C, indicating that DOC has cycled for much longer than DIC in the SCS. The lower Δ 14 C-DIC and Δ 14 C-DOC values at depths shallower than 700 m were mainly influenced by intensified vertical mixing, which upwelled the deep water with low Δ 14 C-DIC and Δ 14 C-DOC values for thorough mixture with the upper layer water. Conversely, the small difference in the Δ 14 C signature in deep water (>1,500 m) between the SCS and the North Pacific confirmed the rapid water exchange through the Luzon Strait and rapid water mixing in the SCS basin, which plays an important role in controlling carbon cycling in the deep SCS.Plain Language Summary Dissolved inorganic carbon (DIC) is the largest carbon pool in the ocean and is closely linked to dissolved organic carbon (DOC), which is the largest exchangeable organic carbon pool in the ocean. Both DIC and DOC play important roles in the global carbon cycle, but their sources, distribution, and cycling time are different and controlled by different processes in the ocean. Here we report radiocarbon and stable carbon isotope measurements of DIC and DOC collected in the South China Sea (SCS) to reveal the sources and cycling time scales of the two major carbon pools in the SCS. The Δ 14 C values and 14 C ages indicate that DOC has cycled for much longer than DIC in the SCS. The rapid water exchange and mixing between the SCS and the Kuroshio Current in the Northwestern Pacific play important roles in controlling the distributions and cycling of DIC and DOC in the SCS.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Radiocarbon in Dissolved Organic and Inorganic Carbon of the South China Sea

Ding

Shan

et al. 2020

JGR Oceans

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“…Similar findings have been obtained by previous studies focused on different regions in the ECS (Hung et al, 2003; and other marginal seas of the NP (Hung et al, 2007;Dai et al, 2009). In our recent study, we have reported that the depth concentrations of DIC and  14 C-DIC values in the ECS slope and the KE region showed conservative behavior and could be used as tracers of water mass movement and water parcel homogenization as predicted by the solution mixing model (Ge et al, 2016;Ding et al, 2018). In Fig.…”

Section: Process Controlling Doc Distribution In the Ecssupporting

confidence: 89%

“…The methods for DIC concentrations and  14 C-DIC measurements have been described in detail in separated papers for the samples collected during the same cruise (Ge et al, 2016;Ding et al, 2018). Briefly, DIC concentrations were measured using a Shimadzu TOC-L analyzer with the total IC mode.…”

Section: Chemical Analysismentioning

confidence: 99%

Influence of hydrodynamic mixing on the distribution of dissolved organic carbon in the East China Sea and the northwest Pacific

Ding

Wang

2018

Preprint

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Abstract. Oceanic dissolved organic carbon (DOC) is one of the largest carbon reservoirs on Earth, and its distribution and behavior play important roles in carbon cycling and biogeochemical processes in the ocean. Here, we report distribution and concentrations of DOC for water samples collected from the shelf-edge and slope regions in East China Sea (ECS) and the Kuroshio Extension (KE) in the northwestern North Pacific (NP) during two cruises in 2014–2015. Concentrations of DOC were 45–88 µM in the ECS and 35–65 µM in the KE. In addition to biological processes, the distribution of DOC is largely controlled by hydrodynamic mixing of different water masses. The intrusion of Kuroshio Current could dilute DOC concentrations at stations in the outer shelf and slope ranges of the ECS. The inverse correlation of DOC with apparent oxygen utilization (AOU) suggests that DOC oxidation only contributes 18 % of the oxygen consumption in the ECS slope waters. In contrast, concentrations of DOC in the KE were significantly lower in surface waters, and a relatively low and stable DOC level (~ 40 µM) was found in deep waters. The observed spatial variations of DOC in the upper 700 m among the stations in the KE were largely influenced by the mixing of the two water masses carried by the two major western boundary currents: Kuroshio and Oyashio that mix and form the KE. The hydrodynamic processes play important roles not only in the distribution of DOC but nutrients as well, thus could have major impact to primary production and ecosystems in the KE region.

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“…In this study, we use the radiocarbon content in dissolved inorganic carbon (DIC) to trace the movement of the Changjiang dilute water and the KBC subsurface water and their interactions off the Changjiang Estuary. Radiocarbon content in water DIC has been used to trace currents movement in the northwest Pacific (Ding et al, 2018;Ge et al, 2016;Tsuboi et al, 2011) and horizontal and vertical mixing processes in the South China Sea (Bolton et al, 2016;Ding et al, 2020;Gao et al, 2018). The vertical profiles of DIC Δ 14 C at the ECS continental slope have shown the upwelling of KC intermediate water onto the outer shelf (Ge et al, 2016).…”

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Hypoxic Effects on the Radiocarbon in DIC of the ECS Subsurface Water

et al. 2021

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The East China Sea (ECS) features the largest continental shelf in the northwest Pacific Ocean, receiving 924 km 3 freshwater annually from the Changjiang (Yangtze) River (CR), which accounts for 90% of the total freshwater input to the ECS (Dai et al., 2011;Qu et al., 2005). Thus, the Changjiang dilute water (salinity less than 31 psu) exerts a great effect on the physical and chemical structure of the ECS shelf (Chen

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Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North Pacific

Cited by 12 publications

References 44 publications

Radiocarbon in Dissolved Organic and Inorganic Carbon of the South China Sea

Radiocarbon in Dissolved Organic and Inorganic Carbon of the South China Sea

Influence of hydrodynamic mixing on the distribution of dissolved organic carbon in the East China Sea and the northwest Pacific

Hypoxic Effects on the Radiocarbon in DIC of the ECS Subsurface Water

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