Salinity, oxygen isotope, hydrogen isotope, and radiocarbon of coastal seawater of North Japan

Kubota, Kaoru; Sakai, Keisuke; Ohkushi, Ken’ichi; Higuchi, Tomihiko; Shirai, Kotaro; Minami, Masayo

doi:10.2343/geochemj.gj22021

Geochem. J.

2022

DOI: 10.2343/geochemj.gj22021

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Salinity, oxygen isotope, hydrogen isotope, and radiocarbon of coastal seawater of North Japan

Kaoru Kubota

Keisuke Sakai

Ken’ichi Ohkushi

et al.

Abstract: To understand seawater properties, such as water mass structure and mixing, geochemical analyses are useful. However, geochemical datasets for seawater that fully cover coastal areas of Hokkaido, North Japan are lacking. Here we report comprehensive geochemical analyses of seawater (salinity, δ 18 O, δD, and Δ 14 C) collected in August-September 2021 from coastal areas of Hokkaido as well as the west coast of Tohoku (Northeast Japan). These datasets are expected to improve our understanding of seawater propert… Show more

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Cited by 2 publications

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First dataset of dissolved inorganic radiocarbon in the Tokara Strait

Lan,

Hirabayashi,

Miyairi

et al. 2023

Geochem. J.

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Radiocarbon ( 14 C) has been widely used to understand the ages in archeology and paleoenvironmental sciences. In marine environments, the dissolved inorganic radiocarbon (expressed as DIC Δ 14 C) of seawater has been used as a reliable tracer in the research of carbon cycling and studies in global to regional water mixing. Here, we present the first highresolution dataset of DIC Δ 14 C values in the Tokara Strait collected at eight stations during a cruise on the Research Vessel (R/V) Hakuho-Maru in March 2022. The DIC Δ 14 C ranges from −211‰ to 28‰ in the upper 1200 m depth of the Tokara Strait. High and modern values (bomb 14 C; DIC Δ 14 C ≥ 0‰) were observed above ~400 m depth at station T3 and above 200 m depth at other stations. These are indicative of the influence of anthropogenic carbon from aboveground nuclear bomb tests conducted in the Pacific Ocean during the 1940s to 1960s. The dataset also includes hydrographic information (temperature, salinity, and density), all of which may help interpret the DIC Δ 14 C variations in the Tokara Strait. These datasets are expected to improve our understanding of water mixing processes and the carbon cycle in the Tokara Strait, which has important implications for understanding climate variability.

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First dataset of dissolved inorganic radiocarbon in the Tokara Strait

Lan,

Hirabayashi,

Miyairi

et al. 2023

Geochem. J.

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Spatiotemporal variations of seawater δ18O and δD in the Western North Pacific marginal seas near Japan

Kodama,

Kitajima,

Takahashi

et al. 2024

Geochem. J.

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The stable oxygen isotope (δ 18 O) values of biogenic calcium carbonates (CaCO3) present in hard tissues of marine organisms vary with the δ 18 O of the surrounding seawater (δ 18 Osw) and water temperature. Consequently, the ambient water temperature when marine organisms existed can be estimated using δ 18 O of CaCO3 with δ 18 Osw. Thus, the aims of this study were to reveal the spatiotemporal variations in δ 18 Osw and their correlations with salinity in the East Asian marginal seas. We collected seawater samples (n = 2222) at 1394 stations around Japan, primarily from the surface layer of the East China Sea (ECS) and Sea of Japan (SOJ), from 2015 to 2021. We analyzed δ 18 Osw and the stable hydrogen isotope of seawater (δDsw) along with the measured water temperature and salinity. The δ 18 Osw and δDsw values ranged from −3.48‰ to +0.45‰, and −21.5‰ to +2.3‰, respectively. In our full data, both δ 18 Osw and δDsw had positive linear relationships with salinity as follows: δ 18 Osw = 0.235 × salinity − 7.94 (r 2 = 0.85) and δDsw = 1.56 × salinity − 52.9 (r 2 = 0.85). Furthermore, the relationship between δ 18 Osw and δDsw for full data as follows: δDsw = 6.44 × δ 18 Osw − 0.18 (r 2 = 0.96). These relationships varied across seasons, areas (the ECS or SOJ), and water depths. In particular, δ 18 Osw and δDsw of less-saline water were different in the ECS and SOJ. These fine-scale, wide-range, and highprecision δ 18 Osw and δDsw datasets can contribute to paleoceanography, environmental analysis, oceanography, and fisheries science.

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Salinity, oxygen isotope, hydrogen isotope, and radiocarbon of coastal seawater of North Japan

Cited by 2 publications

References 36 publications

First dataset of dissolved inorganic radiocarbon in the Tokara Strait

First dataset of dissolved inorganic radiocarbon in the Tokara Strait

Spatiotemporal variations of seawater <i>δ</i><sup>18</sup>O and <i>δ</i>D in the Western North Pacific marginal seas near Japan

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