Kuroshio Meanders in the East China Sea (original) (raw)
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The PI attended three ONR workshops to discuss and help define the future integrated observational program for "Quantifying, Predicting and Exploiting Uncertainty (QPEU), i.e., to help formulate an experiment to study the Kuroshio intrusion, nonlinear internal waves (NLIWs), internal tides, inertial waves, and turbulence mixing resulting from the Kuroshio-topography interaction. Using historical CTD data collected by the National Center for Ocean Research (NCOR) between 1985 and 2002, the PI computed the fluctuations of sound speed in different regions along the Kuroshio path and across the continental shelf and slope. Preliminary analysis concludes that strong sound speed anomalies are induced by NLIWs, internal tides, and processes associated with the Kuroshio interaction with the continental slope and shelf. Such sound speed anomalies have the temporal and spatial scales and characteristics associated with the corresponding oceanic processes. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT b.
Variations of Kuroshio Intrusion and Internal Waves at Southern East China Sea
The PI attended three ONR workshops to discuss and help define the future integrated observational program for "Quantifying, Predicting and Exploiting Uncertainty (QPEU), i.e., to help formulate an experiment to study the Kuroshio intrusion, nonlinear internal waves (NLIWs), internal tides, inertial waves, and turbulence mixing resulting from the Kuroshio-topography interaction. Using historical CTD data collected by the National Center for Ocean Research (NCOR) between 1985 and 2002, the PI computed the fluctuations of sound speed in different regions along the Kuroshio path and across the continental shelf and slope. Preliminary analysis concludes that strong sound speed anomalies are induced by NLIWs, internal tides, and processes associated with the Kuroshio interaction with the continental slope and shelf. Such sound speed anomalies have the temporal and spatial scales and characteristics associated with the corresponding oceanic processes. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT b.
Interannual Modulation of Kuroshio in the East China Sea Over the Past Three Decades
Frontiers in Marine Science
Previous studies have suggested that westward-migrating mesoscale eddies are a dominant factor that modulate the interannual Kuroshio intensity in the East China Sea (ECS), indicating a close positive correlation between them. According to the extended record of altimetry-based sea level anomalies (SLAs) until 2020, however, the interannual variation of the Kuroshio intensity no longer has a strong positive correlation with eddy activity in the subtropical countercurrent (STCC) region since the early 2000s. Our observational analyses showed that the Kuroshio intensity in the ECS can be modulated by the combined effect of westward-migrating mesoscale eddies and westward-propagating oceanic planetary waves from the east. Until the early 2000s, the interannual variability of Kuroshio was mainly affected by eddy migration from the STCC region, associated with oceanic instability driven by large-scale wind patterns over the western North Pacific. Since then, oceanic planetary waves propa...
Observations of Kuroshio flow variations in the East China Sea
Journal of Geophysical Research, 2008
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.
Kuroshio Variability on the Shelf of the East China Sea
Through the ONR-supported project, an array of eleven IESs (inverted echo sounders) has been in operation since December 2002 in the ECS to measure the Kuroshio for a two-year time period, i.e., until the end of 2004. The IES array was deployed in the Okinawa Trough at depths deeper than 500m. The Kuroshio, however, extends to the outer continental shelf (see ). This NICOP project aims
Variation of the Kuroshio in the Tokara Strait Induced by Meso-Scale Eddies
Journal of Oceanography, 2001
Temporal variations of the Kuroshio volume transport in the Tokara Strait and at the ASUKA line are decomposed by phase-propagating Complex EOF modes of highresolution sea surface dynamic topography (SSDT) field during the first tandem period of TOPEX/POSEIDON and ERS-1 (from October 1992 to December 1993). Both variations are dominated by a mode with nearly semi-annual cycle, which indicates a series of interactions between the Kuroshio and meso-scale eddies. Namely, northern part of a westward-propagating meso-scale eddy at 23°N is captured into the southern side of the Kuroshio at the south of Okinawa, then it moves downstream along the Kuroshio path passing the Tokara Strait, and reaches to the ASUKA line where it merges with another eddy propagating from the east at 30°N. The variation at the ASUKA line is, however, less dominated by this mode; instead, it includes the SSDT variations in the south of Shikoku and the east of Kyushu which would be directly affected by eddies from the east without passing the Tokara Strait. On the other hand, the same analysis for movements of the Kuroshio axis in the Strait indicates that they are governed by short-term variations locally confined to the Kuroshio in the East China Sea without being induced by meso-scale eddies. This results, however, seem to depend strongly on a time scale of interest. It is suggested that the long-term movements of the Kuroshio axis in the Strait would demonstrate coincidence with SSDT variation in the south of Japan. Comparing with numbers of studies on the possible effects of the Tokara Strait to the Kuroshio in the south of Japan, causes of the variations are less well understood. Variations of the Kuroshio in the Tokara Strait are considered to be originated from variations of the Kuroshio in the East China Sea where downstream propagation of signals is often observed (e.g. Qiu et al., 1990; Ichikawa and Beardsley, 1993). Interannual variations of the Kuroshio volume transport in the East China Sea seem to be originated from the upstream region of the Kuroshio (17°-21°N), and to be induced by wind stress changes to the far east (Akitomo et al., 1996). Recently, higher-frequency variations of the Kuroshio volume transport in the east of Taiwan are suggested to be coincident with westward-propagating meso-scale eddies (Zhang et al., 2000). However, detailed understanding of the response of the Kuroshio in the Tokara Strait to meso-scale eddies has not been achieved at this stage. In addition, Feng et al. (2000) found no significant coincidence in the upstream sea surface dynamic topography (SSDT) with longterm meridional shift of the Kuroshio axis in the Tokara
Nonlinear internal wave spirals in the northern East China Sea
Scientific reports, 2018
Oceanic internal waves are known to be important to the understanding of underwater acoustics, marine biogeochemistry, submarine navigation and engineering, and the Earth's climate. In spite of the importance and increased knowledge of their ubiquity, the wave generation is still poorly understood in most parts of the world's oceans. Here, we use satellite synthetic aperture radar images, in-situ observations, and numerical models to (1) show that wave energy (having relatively high amplitude) radiates from a shallow sill in the East China Sea in all directions, but with a significant time lag dependent on background conditions, (2) reveal that wave fronts are locally formed with often favorable conditions for re-initiation, and (3) demonstrate the resulting variety of wave patterns. These findings would be the case for any broad shelf having shallow sills with time-varying conditions, and therefore have significant implications on the redistribution of energy and materials ...
Response of ocean dynamics to multiple equilibria of the Kuroshio path South of Japan
Dynamics of Atmospheres and Oceans, 2019
Variability of the Kuroshio path to the south of Japan plays a central role in the local climate change and exerts tremendous influences on the local atmosphere and ocean. In this study, the response of ocean dynamics, in terms of the eddy kinetic energy (EKE), potential vorticity (PV), relative vorticity, and eddy-mean flow interaction, to the Kuroshio path change is discussed. Kuroshio path south of Japan includes the near-shore non-large meander (nNLM), the offshore non-large meander (oNLM), and the typical large meander (tLM). Analyses reveal that the distribution of EKE, PV, relative vorticity, and energy exchange between the eddy field and the mean flow respectively varies with the Kuroshio path: (1) The tLM has the maximum EKE along the path; (2) The positive and negative PV are located at the onshore and offshore side of Kuroshio axis, respevetively; (3) The distributions of anomalous relative voritcity of nNLM, oNLM, and tLM are consistent with sea surface height anomalies (SSHAs); (4) The tLM has the largest energy exchange between the eddy field and the mean flow in terms of the rate of barotropic energy conversion. On the other hand, the stability analysis of ocean currents suggests that the three Kuroshio paths south of Japan have their own intrinsic properties of the instability.