The mesoscale eddies and Kuroshio transport in the western North Pacific east of Taiwan from 8-year (2003–2010) model reanalysis

Abstract

The relationship between the Kuroshio volume transport east of Taiwan (~24°N) and the impinging mesoscale eddies is investigated using 8-year reanalysis of a primitive equation ocean model that assimilates satellite altimetry and SST data. The mean and fluctuations of the model Kuroshio transport agree well with the available observations. Analysis of model dynamic heights and velocity fields reveals three dominant eddy modes. The first mode describes a large eddy of~500 km in diameter, centered at 22°N. The second mode describes a pair of the north-south counter-rotating eddies of~400 km in diameter each, centered at 23°and 20°N, respectively. The third mode describes a pair of the east-west counter-rotating eddies of~300 km in diameter each, centered at 21°N. The associated velocity fields indicate eddies extending to 600-700 m in depth with vertical shears concentrated in the upper 400 m. All three modes and the model Kuroshio transport have similar dominant timescales of 70-150 days and generally are coherent. The decreased Kuroshio volume transports typically are associated with the impinging cyclonic eddies and the increased transports with the anticyclonic eddies. Selected drifter trajectories are presented to illustrate the three eddy modes and their correspondence with the varying Kuroshio transports.

Modulation of Kuroshio transport by mesoscale eddies at the Luzon Strait entrance

“…For example, between 24 June and 4 July 2012, the Kuroshio transport increased from 7 Sv to 22 Sv. Similar transport variations of greater than 10 Sv on O(10 days) time scales were detected during May and June 2013, which is much faster than the O(100) day variations observed by Zhang et al [2001] and Lee et al [2013].…”

“…Figure 1c shows the map of absolute dynamic topography (MADT) and Aviso surface current. Previous studies report that Kuroshio transport east of Taiwan is modulated strongly by the westward propagating eddies at a time scale O(100 days) [Yang et al, 1999;Johns et al, 2001;Zhang et al, 2001;Lee et al, 2013;Chang and Oey, 2012]. Anticylonic (cyclonic) eddies increase (decrease) Kuroshio transport.…”

Effects of the STCC eddies on the Kuroshio based on the 20-year JCOPE2 reanalysis results

“…Using the cruise XBT/XCTD data from south of Taiwan (21-22°N), Gilson and Roemmich (2002) observed that the Kuroshio geostrophic transport is reduced with the approach of the cyclonic eddies, while the warm eddies correspond to the strengthening of transport. The 8-year modeling simulation of Lee et al (2013) showed that the Kuroshio transport variation east of Taiwan ($24°N) is related to the impinging eddies. Using observed 1-year mooring data, a recent study by Lien et al (2014) suggested that the Kuroshio transport near the Luzon Strait (18.75°N) is modulated by the eddies.…”

Impacts of Tides and Typhoon Fanapi (2010) on Seas Around Taiwan

“…EASNFS analysis has been previously applied in several studies to the western North Pacific. In seas around Taiwan, it has been applied to investigate the impact of typhoons on the upper ocean temperature , upwelling off the southern coast of Taiwan (Ko et al 2009), thermal structures in the South China Sea (Chang et al 2010), and the impact of eddies on the Kuroshio transport along the east coast of Taiwan (Lee et al 2013).…”