Effective Depths of Mesoscale Eddies in the Waters Adjacent to Eastern Taiwan

• Main Authors: Lu, Ching-Yuan, 盧靖元
• Other Authors: Ho, Chung-Ru
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/jgf78a

碩士 === 國立臺灣海洋大學 === 海洋環境資訊系 === 105 === Westward propagating mesoscale eddies originated by the instability of subtropical countercurrent intrude into the Kuroshio region and form an eddy rich zone east of Taiwan. These eddies may transfer heat vertically through downwelling or upwelling process. To understand the effective depths of mesoscale eddy are thus very important. The position of an oceanic eddy is determined with sea level anomaly (SLA) data which is derived from satellite altimetry by an objective detection method using the Okubo-Weiss algorithm. Temperature-salinity profile from ocean glider and Conductivity Temperature Depth (CTD) data during 1998–2013 are also employed in this study. Twelve warm eddies and six cold eddies were found in this period when in-situ measurements were also available. The results show that effective depths are most located at 100-300 m with an average of 181 m. The SLA of warm eddy center is strongly related to the effective depth with a correlation coefficient of 0.85 (p<0.05), but no significant relationship is found to cold eddy. Numerical model data are also used in this study, and the result is similar to that from in-situ measurements. The average of effective depth is 199 m. A histogram of effective depth shows that the proportion of effective depth shallower than 100 m at 122°E (28.7%), where is at the Kuroshio region, is less than the proportion of that in the whole research region (43.0%). This is probably caused by the high speed of sub-surface currents which may deepen the effective depth at the Kuroshio region.