The Kuroshio bifurcation associated with islands at the Luzon Strait

Abstract

Based upon a suite of satellite and hydrology data along with numerical model simulations, the Kuroshio is found to be separated into two branches. The two branches are located on the western and eastern sides of the Batanes Islands. The western branch, which is the main branch of the Kuroshio, is estimated to carry roughly 68% of the transport, while the eastern branch, which has not been reported before, carries the remainder. Both branches bring warmer water northward, producing two separate warm tongues east of the Luzon Strait. The western warm tongue has an obvious seasonal variation due to the seasonal variation of the Kuroshio in the northern Luzon Strait, while the eastern warm tongue is associated with Pacific mesoscale eddies. As an anticyclonic (a cyclonic) eddy approaches the Batanes Islands from the east, the eastern branch of the Kuroshio is strongly intensified (weakened), and a more (less) pronounced warm tongue is induced. Consequently, interannual variability of Pacific mesoscale eddies affects the strength of the eastern branch.

Observed cold filaments associated with mesoscale eddies in the South China Sea

“…A simple mixed layer model [ Qu , ] is used to investigate the formation mechanisms of the cold filaments. The model is based on the mixed layer temperature equation [ Wang et al ., ; Sun et al ., ], except that only the geostrophic component of the advection of mixed layer temperature is included. Consequently, the equation for the mixed layer temperature tendency is where T is the SST or the mixed layer temperature, t is time; x and y are the conventional Cartesian coordinates, and are the geostrophic components of ocean velocity in x and y directions, respectively.…”

“…A simple mixed layer model [Qu, 2001] is used to investigate the formation mechanisms of the cold filaments. The model is based on the mixed layer temperature equation [Wang et al, 2012;Sun et al, 2016], except that only the geostrophic component of the advection of mixed layer temperature is included. Consequently, the equation for the mixed layer temperature tendency is @T @t 52 u g @T @x 1v g @T @y…”

The Four Patterns of the East Branch of the Kuroshio Bifurcation in the Luzon Strait

“…Affected by the Kuroshio, monsoon, mesoscale eddies, and topography, the circulation in the LS is very complicated, and has been studied extensively in previous literatures [8,9,12]. These studies have specifically discussed the interaction between the Kuroshio and mesoscale eddies: (1) the Kuroshio can generate mesoscale eddies by its own variation [11,13]; (2) the Kuroshio can affect mesoscale eddies in the NWP into the South China Sea [7,9]; (3) mesoscale eddies can alter the Kuroshio current field [8,10,14]; (4) interaction between the Kuroshio and mesoscale eddies can influence the local marine environment [14,15]. Although there are many related studies, some questions involving small and moderate ocean phenomena in the LS remain unclear.…”

“…The accumulation of high-resolution satellite remote sensing data enables us to better study small and moderate ocean phenomena. Based on high-resolution satellite remote sensing data and hydrological data along with numerical model simulations, the Kuroshio bifurcation phenomena in the LS has been put forward: The Kuroshio in the LS bifurcates into two branches located on the western and eastern sides of the Batanes Islands, and produces two warm tongues east of the LS [14]. The western branch is the main part of the Kuroshio, and its temporal and spatial variability has been widely studied [16][17][18][19].…”

“…The western branch is the main part of the Kuroshio, and its temporal and spatial variability has been widely studied [16][17][18][19]. However, the temporal and spatial variability of the eastern branch has hardly been studied and remains unclear, although its intensity is related to mesoscale eddies in the NWP [14]. The Kuroshio transports warm water from low latitudes to middle latitudes, so it can cause temporal and spatial variability of local sea temperature in most cases [14,16].…”