Rapid water parcel transport across the Kuroshio Extension in the lower thermocline from dissolved oxygen measurements by Seaglider

Progress in Earth and Planetary Science

Shigeki Hosoda¹  Ryuichiro Inoue¹  Mizue Hirano¹  Yoshikazu Sasai¹  Hideharu Sasaki²  Masami Nonaka² 

[1] Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, 237-0061, Yokosuka, Kanagawa, Japan;Research Institute for Value-Added-Information Generation, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, 237-0061, Yokosuka, Kanagawa, Japan;

关键词: Seaglider;    Small water parcels;    Water mass exchange;    Kuroshio Extension;    Mesoscale eddy;    Submesoscale;    Dissolved oxygen;   

DOI  :  10.1186/s40645-021-00406-x

来源: Springer

【 摘 要 】

Small water parcels, which are characterized by a low salinity and high dissolved oxygen (DO) are observed by Seaglider in the main thermocline (26.0–27.0 σθ) south of the Kuroshio Extension (KE), have horizontal and vertical scales of a few tens of kilometers and a few tens of meters, respectively. Water mass analyses revealed larger negative salinity anomalies (<− 0.05) and positive DO anomalies (> 15 μmol kg−1) than those of the surrounding water. The characteristics are similar to those of water mass with low salinity and high DO in the subpolar Northwestern Pacific Ocean. Additionally, higher DO anomaly water parcels appear in the upper layer (< 26.7 σθ) while low salinity parcels appear in the lower layer (> 26.7 σθ). Oxygen consumption rates from the apparent oxygen utility suggest that the small water parcels consume less oxygen than the surrounding water, implying that they migrate in a shorter time across the KE after subduction and their characteristics may reflect the sea surface temperature, salinity, and DO in the subduction region. Similar small water parcels represented by high-resolution numerical simulations indicate that they pass through the KE in 1 month. The simulations support the oxygen consumption rate from the Seaglider observations. The existence of a fast process for water mass migration via meso- and submesoscale subduction processes across the KE affects the amount, subduction, and exchange process of water mass. Our study indicates that a small water mass contributes to the exchange process across the KE rapidly, which had not been identified in previous studies. Consequently, detailed observations using multiple Seagliders should capture detailed spatial and temporal variability of the water mass exchange process.

【 授权许可】

CC BY