NTU HIGHLIGHTS April 2018  
     
  Research Achievements  
 
 

Journal Cover Article Explains Flow Variations in the Kuroshio Current

 

A study explaining flow variations in the Kuroshio current in the Pacific Ocean east of Taiwan was published as the cover article inthe January issue of the academic journal Deep Sea Research Part I: Oceanographic Research Papers.The study’sfindings have implications for the development of ocean current energy, management of fisheries, study of global climate change, and understanding of the evolution of typhoons.
The article, “Zonal Migration and Transport Variations of the Kuroshio East of Taiwan Induced by Eddy Impingements,” explains the basic physical dynamics underlying the meandering flow and transport variability of the Kuroshio current east of Taiwan.
Prof. Ming-Huei Chang, principal author, and his research team at the Institute of Oceanography relied on the accumulation of a massive dataset to arrive at their comprehensive conclusions. To collect data for the study, the team measured the Kuroshio current continuously for an unprecedented 23 months using three acoustic Doppler current profilers moored approximately 50 km south of the PCM-1 line.
The Kuroshio current is the western boundary current in the Northwest Pacific Ocean. It transports a tremendous volume of heat, salt, and water mass from the east of Luzon Island to the south of Japan, passing the east coast of Taiwan en route. It exercises a major impact on the marine environment, weather, and global climate change.
Research on the Kuroshio is important because it helps us to understand the dynamics of the Kuroshio current’s variability and how to predict its probable influence on the marine environment and weather/climate.
The earliest long-term data set concerning the Kuroshio current wascollected by an array of moored current-meters placed along the PCM-1 line in the East Taiwan Channel during the World Ocean Circulation Experiment conducted from September 1994 to May 1996. Such data collection at the PCM-1 provided insight into the variability of the Kuroshio current, and supported further studies of the Kuroshio current for the past 20 years.
The threemain highlights of Prof. Chang’s findings are:

  1. The Kuroshio transport is 4.3 Sv (1 Sv=1 million cubic meter per second) lower than that observed at the PCM-1 line, presumably due to interannual variations related to the abundance of mesoscale eddies in the Subtropical Counter Current region.
  2. The observations exhibit more energetic Kuroshio variability in its axis migration at the KTV1 than at the PCM-1 line. The relatively stable Kuroshio in PCM-1 is attributed to the presence of the East Taiwan Channel and the Ryukyu Islands chain, where the topography behaves as a regulator that dampens the interaction with eddies in PCM-1.
  3. Transport variability east of Taiwan is mostly caused by Kuroshio-eddy interactions.