[A-CG32] Extratropical oceans and atmosphere

[ACG32-P13] Double structure of ocean barrier layers observed under heavy rainfall on the Kuroshio front in the East China Sea

*Tetsutaro Takikawa¹, Yoshihiro Tachibana², Hirohiko Nakamura³, Ayako Nishina³, Atsuyoshi Manda², Hatsumi Nishikawa⁴, Kasuga Satoru², Yuta Ando⁵, Teruyuki Kato⁶ (1.Nagasaki University, 2.Mie University, 3.Kagoshima University, 4.Tokyo University, 5.Kyushu University, 6.Meteorological Research Institute)

Heavy rainfall on the ocean forms a lens-shaped low-salinity layer on the sea surface (e.g. Drushka et al., 2016, JGR). It is difficult to observe the horizontal and vertical structure of the low-salinity pool. Cao et al. (2022), Remote Sens., showed the existence of a barrier layer below the low-salinity pool in the South China Sea from satellite and ship-track observations. The barrier layer, defined as the difference between the surface mixed layer depth (MLD) and the isothermal layer depth (ILD), is thick in tropical regions with a large precipitation, and restricts heat transport from the ocean surface to the lower layers (e.g. Katsura et al., 2021, JGR). On the other hand, a large amount of fresh water is discharged from the Changjiang, a major river in mainland China, into the East China Sea. Moon et al. (2019), PIO, reported that the barrier layer was observed under the Changjiang diluted water.
In this study, the spatial three-dimensional structure of low-salinity water on the Baiu and Kuroshio fronts is shown using intensive observation results by three training ships in the East China Sea. The surface low-salinity pool was formed by rainfall during the observations. The barrier layer existed below the low-salinity pool, and other low-salinity patches were observed below the barrier layer. Below the low-salinity patches, we detected temperature inversion layer with warm and saline water, which is thought to have an effect similar to the barrier layer.