In 2015, with a vision of future observational technologies, the MOST sponsored the Marine Exploration Instrument Center at National Taiwan University (NTU) to purchase a Kongsberg Seaglider under the MOST granted integrated project “Observations of the Kuroshio Transport and Variability (OKTV).” The glider was aimed to collect data of hydrography, dissolved oxygen, fluorescence (can be converted to chlorophyll concentration) and back scatter of light in the water. Tasked with testing and piloting the drone, a research team at NTU’s Institute of Oceanography has successfully navigated the glider in the Kuroshio east of Taiwan from December 2016 to March 2017. During its 87-day survey, the glider completed 434 dives along two triangle tracks with a total horizontal distance of about 2,095 km.
This high-resolution hydrographic data set helped the research team found dramatic interleaving layers in the hydrographic section beneath the Kuroshio’s primary velocity core. This observation revealed that two dissimilar water masses that encountered in the Kuroshio between 500 and 800 m depth did not blend together quickly; instead, initial disturbances in their interfaces generated intrusions of the two water masses to each other through a double-diffusive process, forming interleaving layers. Each interleaving layer ranges from 10 to 100 km long with a thickness of about 50 m. The research is unprecedented in the research of submesoscale processes in the ocean. This finding and associated dynamic analysis was published in the Nature series journal Scientific Reports (https://rdcu.be/bNa16) on 6 August.
Indeed, more and more studies have indicated that submesoscale processes such as those observed in the Kuroshio are key to shaping physical, biological, and biogeochemical parameters in the ocean, which are crucial to global climate change projections. The team’s first glider observations inspire not only novel physical and biogeochemical research topics related to the western boundary currents, but also new dynamic parameters for improving the prediction of climate models.
The operation of the glider and observation of the Kuroshio helped the research team expose to the international community, and, consequently, the team was invited to join the global OceanGliders Boundary Ocean Observing Network (BOON), taking the responsibility for long term observing the Kuroshio off the east coast of Taiwan. The team leader－Director Sen Jan of the institute－were also invited to be the member of the BOON Steering Team. For a bit of history, OceanGliders (oceangliders.org) was started in September 2016, and is a component of Global Ocean Observing System (GOOS) under the Technical Commission for Oceanography and Marine Meteorology (JCOMM) of UNESCO.The Seaglider also enhances the mobility of typhoon observation network in the western North Pacific, as well as its capabilities in providing real time hydrographic data and associated applications. Accordingly, the Seaglider, featuring quasi-artificial intelligence and seakeeping qualities, deserves to promote as a state-of-the-art tool to many other oceanographic research.