Observations of Kuroshio flow variations in the East China Sea

Abstract

[1] Kuroshio velocity structure and transport in the East China Sea (ECS) were investigated as part of a 23-month study using inverted echo sounders and acoustic Doppler current profilers (ADCPs) along the regularly sampled PN-line. Flow toward the northeast is concentrated near the continental shelf with the mean surface velocity maximum located 30 km offshore from the shelf break (taken as the 170 m isobath). There are two regions of southwestward flow: a deep countercurrent over the continental slope beneath the Kuroshio axis and a recirculation offshore which extends throughout the whole water column. There is a bimodal distribution to the depth of maximum velocity with occurrence peaks at the surface and 210 dbar. When the maximum velocity is located within the top 80 m of the water column, it ranges between 0.36 m/s and 2.02 m/s; when the maximum velocity is deeper than 80 m, it ranges between 0.31 m/s and 1.11 m/s. The 13-month mean net absolute transport of the Kuroshio in the ECS is 18.5 ± 0.8 Sv (standard deviation, s = 4.0 Sv). The mean positive and negative portions of this net flow are 24.0 ± 0.9 Sv and À5.4 ± 0.3 Sv, respectively.

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

“…The good agreement suggests that the Kuroshio transport is quite stationary in the interannual time scale. The total mean transport of 24.4 Sv also agrees with the Kuroshio transport in the East China Sea at 28°N, 24.0±0.9 Sv, based on 13-month-long (November 2003 to November 2004) combined velocity and sea level observations (Andres et al 2008b). Figure 4 also displays the latitude-time plot of the 8-year model dynamic heights.…”

Manifestation of the Pacific Decadal Oscillation in the Kuroshio

“…Vertically integrated transport of the ECS-Kuroshio near 28°N (KT) is available at 10-day interval through calibration of satellite altimetry data with net absolute transport determined using 13 months of in situ measurements from pressure-sensorequipped inverted echo sounders (PIESs), ADCPs, current meters, and hydrocasts [Andres et al, 2008a[Andres et al, , 2008b. A similar vertically integrated transport time series has been determined for the Ryukyu Current near 26°N, RT [Zhu et al, 2004].…”

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

“…The current velocity in hydrothermal plume water columns in the southern Okinawa Trough is significantly more variable, and of higher magnitude (0.016 to 0.963 m s −1 ), than that in the middle Okinawa Trough (Table 1; Figure 2(a)); this trend is consistent with Kuroshio current velocity patterns (e.g., [58]). When the maximum velocity of the Kuroshio current is located within the top 80 m of the water column, it ranges from 0.36 to 2.02 m s −1 ; when the maximum velocity is below 80 m, it ranges from 0.31 to 1.11 m s −1 [33]. Thus, the velocity of the Kuroshio current reduces from the southern Okinawa Trough to the middle Okinawa Trough (e.g., [58]), suggesting that the current variations of hydrothermal plume water in the Okinawa Trough are controlled by spatial variations in the intensity and position of the Kuroshio current (e.g., [33,58,59]).…”

“…The current flows east of Taiwan and northwards along the Okinawa Trough (e.g., [31]), with a maximum speed of 1 m/s and a width of 100 km [32]. Seawater transported by the Kuroshio current flows from 19 to 47 Sv (Sverdrup, 1 Sv = 10 6 m 3 /s) in the East China Sea [28,[33][34][35] and is an important source of heat for the atmosphere in the global heat balance [36]. Changes in the intensity and volume input of the Kuroshio current can significantly influence seawater character, biogeochemical cycles, and climate in the northwestern Pacific (e.g., [26,27,[37][38][39][40]).…”