This study investigated the vertical structure of an anticyclonic eddy (AE) in the northern South China Sea (SCS) in August 2017 and its response to Typhoon Hato using underwater glider data and satellite altimeter data. Additionally, comparative experiments with and without typhoon forcing were conducted using the Regional Ocean Modeling System (ROMS) for supplementary analysis. The observational results reveal that the maximum temperature and salinity differences between the center and edge of the upper layer of the AE did not occur at the sea surface but near the 100 m depth, with a maximum temperature difference of 2.86°C and a maximum salinity difference of 0.65 PSU. The typhoon caused a significant temperature decrease above 200 m, with the maximum cooling (~2°C) occurring near 50 m. Near this depth, salinity initially increased due to upwelling but later decreased due to surface mixing. The most pronounced cooling and salinity changes occurred one day after the typhoon passage, followed by a gradual deepening of the mixed layer over the next four days, with conditions below the mixed layer largely returning to pre-typhoon states. The numerical simulations indicate that upwelling rapidly intensified during the typhoon’s passage, consistent with the observational temperature changes in the upper ocean. The typhoon’s wind stress increased kinetic energy at the AE site, while the input of positive vorticity reduced absolute vorticity, disrupting the surface anticyclonic flow structure. One day after the typhoon, the flow field gradually recovered.
Ma et al. (Tue,) studied this question.
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