Observing an anticyclonic eddy in the South China Sea using multiple underwater gliders

Mesoscale eddies, as a considerable contributor to the transport of ocean heat, dissolved oxygen and other biochemical tracers, have an important influence on the distribution of marine resources and global climate change. The purpose of this research is to capture the high variability of an anticyclonic eddy in South China Sea to observe its thermohaline vertical structure in different transections. 12 ‘Petrel II’ gliders developed by Tianjin University were deployed in a northern area of the South China Sea during August 4-August 29, 2017 to observe the dynamics of eddies. Combining the high resolution in situ dataset collected by gliders and the monthly averaged climatological temperature and salinity provided by the World Ocean Atlas 2013 (WOA13), the vertical structure of the eddy has been observed. The eddy lasted more than 20 days from August 2 to August 24, 2017. The properties of the water mass in the anticyclonic eddy are similar to the Kuroshio water indicating that the eddy may generate in Kuroshio. The eddy can penetrate 700m depth. Crossing the eddy from northeast to southwest, the maximum anomalies of potential temperature, salinity and potential density were about $3^{\circ} C$ at about 120m, 0.5psu at about 50m, and negative 0.6kg/m
³
at about 150m, respectively. The anomalies distributions of potential temperature, salinity and potential density in the northwest and southeast of the eddy have great similarity. However, the magnitude of anomalies in the northwest are higher than those in the southeast of the eddy. Based on the sea level anomaly (SLA) from satellite altimeter data distributed by Copernicus Marine Environment Monitoring Service (CMEMS), the eddy was moving towards west during the experiment period.