Characterization of water masses around the southern Ryukyu Islands based on isotopic compositions

• DOI: 10.1186/s40645-022-00503-5
• Publication Date: 2022-08-17T11:04:20Z
• Authors: Andros Daniel Cru...; Hideko Takayanagi; Shigeyuki Wakaki; Tsuyoshi Ishikawa; Toshihiro Miyajima; Hitomi Wakaki; Takuya Itaki; Yasufumi Iryu
• Keywords: Circumpolar deep water; Trough (economics); Subsurface Flow

Abstract We investigated the water-mass structure on Okinawa Trough and Pacific sides of southern Ryukyu Island Arc (Yonaguni, Iriomote, Ishigaki subareas) using Nd isotope composition ( 143 Nd/ 144 ratios; expressed as εNd values) benthic foraminiferal tests in surface sediments, which reflect bottom-water composition, along with hydrogen oxygen compositions (δD δ 18 O values, respectively) physical properties (temperature salinity) seawater. The side has lower values than due to continental/island material inputs characterized by relatively low values. Moreover, within Trough, other processes control behavior seawater primarily affect Yonaguni Iriomote subareas, follows. (1) Surface subsurface waters are influenced Taiwanese river discharge combined temporospatial variations oceanographic conditions including Kuroshio Current meandering. (2) Intermediate water is (down − 8.2), possibly attributable sediment plumes turbiditic fluxes. (3) bottom indicate upwelling vertical mixing, therefore being similar those intermediate water. profiles better defined side. High occur (< 300 m depth, potential density < 25.0 kg −3 ) waters, 7.0) subsurface–core-intermediate (400–600 26–27 ). increase slightly 4.0 below 750 depth remain constant down about 2000 deep shows a slight decrease bottom/deep distinguished from upper layers their δD