NTU Study Records Tremendous Variability in Kuroshio Current

An NTU oceanic study has shown that the Kuroshio Current is far more unstable than previously assumed. This important observation was published in the Journal of Geophysical Research - Oceans, featured as a Spotlight article on the journal’s website, and reported on the Eos Earth & Space Science News magazine.

The Kuroshio Current, which is known as the “Gulf Stream” of the Pacific, is a subtropical gyre at the western boundary of the North Pacific. Carrying a tremendous amount of water northwards, the current is in charge of transporting heat and salt from the tropical south to extratropical oceans. The Kuroshio plays an important role in terms of the environment, climate, and fisheries around the coastal regions of Northeast Asia; it also serves as the basis for the region’s weather prediction and management of fishery resources.

Despite its basin-wide importance, little in-situ measurements of the current has been made east of Taiwan. With this in mind, the NTU research team set out on a three year project that took it on 9 voyages between 2012-14 to gather data on the Kuroshio’s velocity, volume, flow structure, heat, and salt transport.

The data revealed a tremendous variability in this boundary current, including a maximum velocity varying between 0.7 and 1.4 meters/second, as well as a depth that fluctuates between 20-100 meters. In addition, the data shows that the distance between Taiwan's east coast and the maximum velocity position varies from 12 to 103 kilometers, and the current's width, as delineated by the 0.2 meters/second velocity contour, varies from 85 to 135 kilometers.

According to the researchers, this newly discovered in-situ data set is vital to the dynamic study of the Kuroshio variability and the validation of numerical simulations.

Members of the study includes Prof. Sen Jan (詹森), Yiing-Jang Yang (楊穎堅), Ming-Huei Chang (張明輝), and Joe Wang (王胄) of the Institute of Oceanography. The study was conducted under the Observations of the Kuroshio Transports and their Variability (OKTV) project, which was sponsored by the Ministry of Science and Technology.