Submesoscale Eddy and Frontal Instabilities in the Kuroshio Interacting With a Cape South of Taiwan. Issue 5 (8th May 2020)

• Record Type: Journal Article
• Authors: Cheng, Yu‐Hsin; Chang, Ming‐Huei; Ko, Dong S.; Jan, Sen; Andres, Magdalena; Kirincich, Anthony; Yang, Yiing Jang; Tai, Jen‐Hua
• Is Part Of: Journal of geophysical research. Volume 125:Issue 5(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-05-08
• Subjects: Kuroshio -- submesoscale eddy -- headland -- recirculation -- eddy corotation -- barotropic instability; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2020JC016123
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: The processes underlying the strong Kuroshio encountering a cape at the southernmost tip of Taiwan are examined with satellite‐derived chlorophyll and temperature maps, a drifter trajectory, and realistic model simulations. The interaction spurs the formation of submesoscale cyclonic eddies that trap cold and high‐chlorophyll water and the formation of frontal waves between the free stream and the wake flow. An observed train of eddies, which have relative vorticity about one to four times the planetary vorticity ( f ), is shed from the recirculation that occurs in the immediate lee of the cape as a result of flow separation. These propagate downstream at a speed of 0.5–0.6 m s −1 . Farther downstream, the corotation and merging of two or three adjacent eddies are common owing to the topography‐induced slowdown of eddy propagation farther downstream. It is found that the relative vorticity of a corotating system (1.2 f ) is 70% weaker than that of a single eddy due to the increase of eddy diameter from ~16 to ~33 km, in agreement with Kelvin's circulation theorem. The shedding period of the submesoscale eddies is strongly modulated by either diurnal or semidiurnal tidal flows, which typically reach 0.2–0.5 m s −1, whereas its intrinsic shedding period is insignificant. The frontal waves predominate in the horizontal free shear layer emitted from the cape, as well as a density front. Energetics analysis suggests that the wavy features result primarily from the growth of barotropic instability in the free shear layer, which may play a secondary process in the headland wake. Key Points: Recirculation flow is induced, shedding submesoscale cyclonic eddies Headland eddy generation is influenced by the Kuroshio and tidal flows Eddies corotate and merge further downstream