Dissolved barium as a tracer of Kuroshio incursion in the Kuroshio region east of Taiwan Island and the adjacent East China Sea

From May to June 2014, the geochemical characteristics of dissolved barium(Ba) in sea water and its influx from the Kuroshio into the East China Sea(ECS) were studied by investigation of the Kuroshio mainstream east of Taiwan Island and the adjacent ECS. This allowed for the scope and extent of the Kuroshio incursion to be quantitatively described for the first time by using Ba as a tracer. The concentration of Ba in the Kuroshio mainstream increased gradually downward from the surface in the range 4.91–19.2 μg L.1. In the surface layer of the ECS, the Ba concentration was highest in coastal water and gradually decreased seaward, while it was higher in coastal and offshore water but lowest in middle shelf for bottom layer. The influx of Ba from Kuroshio into the ECS during May to October was calculated to be 2.19×108 kg by a water exchange model, in which the subsurface layer had the largest portion. The distribution of Ba indicated that Kuroshio upwelled in the sea area northeast of Taiwan Island. The north-flowing water in the Taiwan Strait restrained the incursion of Kuroshio surface water onto the ECS shelf, while Kuroshio subsurface water gradually affected the bottom of the ECS from outside. The results of end member calculation, using Ba as a parameter, showed that the Kuroshio surface water had little impact on the ECS, while the Kuroshio subsurface water formed an intrusion current by climbing northwest along the bottom of the middle shelf from the sea area northeast of Taiwan Island into the Qiantang Estuary, of which the volume of Kuroshio water was nearly 65%. Kuroshio water was the predominant part of the water on the outer shelf bottom and its proportion in areas deeper than the 100 m isobath could reach more than 95%. In the DH9 section(north of Taiwan Island), Kuroshio subsurface water intruded westward along the bottom from the shelf edge and then rose upward(in lower proportion). Kuroshio water accounted for 95% of the ocean volume could reach as far as 122°E. Ba was able to provide detailed tracing of the Kuroshio incursion into the ECS owing to its geochemical characteristics and became an effective tracer for revealing quantitative interactions between the Kuroshio and the ECS.     

Oxygen depletion off the Changjiang (Yangtze River) Estuary

In a survey on the Yellow Sea and the East China Sea on August 20-30 of 1999, we found a hypoxic zone (<2 mg/L) of 13700 km² with an average thickness of 20m at the bottom of the Changjiang (Yangtze River) Estuary, with an oxygen minimum value of 1 mg/L. The extension of the dissolved oxygen deficiency extended to the 100m isobath in a southeastward direction along the bottom of the continental shelf of the East China Sea. During the last two decades, the minimum dissolved oxygen values in the low oxygen region of the Changjiang Estuary have decreased from 2.85 mg/L to 1 mg/L. In the hypoxic zone, the apparent oxygen utilization (AOU) was 5.8 mg/L and the total oxygen depletion approximately 1.59 × 10⁶t. The strong halocline above the hypoxic zone, as a result of affluent water from the Changjiang, Taiwan Warm Current (TWC), and the high concentrations of particle organic carbon (POC) and nitrogen (PON) are the major factors causing the formation of the hypoxic zone. The POC: PON ratios and nutrient concentration distributions in the hypoxic zone suggest that the oxygen deficiency in the bottom water during the summer in the East China Sea off the Changjiang is the result of organic carbon production enhanced by nutrients from the Changjiang and fluvial organic matter input, followed by a shift in regeneration of nutrients in the East China Sea.     

An altimetric transport index for Kuroshio inflow northeast of Taiwan Island

The Kuroshio inflow northeast of Taiwan Island plays an important role in the heat and nutrient balances over the East China Sea(ECS). Based on merged satellite altimeter data and the PCM-1 mooring observation at the East Taiwan Channel(ETC), the study employs a correlation iteration scheme to find the optimal transport index for the Kuroshio inflow. The sea level difference with the highest correlation to the ETC transport is across the ECS shelf break rather than along the PCM-1 line. The counter-intuitive result is caused by large signal noise and poor track coverage of altimeters near the Taiwan coast. The optimal altimetric index is highly correlated with the two-year in-situ measurements as well as the ten-year output of the global assimilation model. It serves as a better estimator of Kuroshio inflow than those using tidal gauge data, and helps pinpoint a 5 cm mismatch of mean sea level in the Keelung tidal record. The mean transport of Kuroshio inflow based on the twenty-year altimetric index is 20.55 Sv with a standard deviation of 3.05 Sv. Wavelet spectrum of the index reveals that semi-annual period dominates the Kuroshio variation northeast of Taiwan Island.     

226Ra distribution in the Antarctic Ocean

²²⁶Ra data on eleven vertical profiles taken during the GEOSECS program from the Antarctic Ocean and its vicinity in both the Atlantic and the Pacific are presented. Replicate measurements were made on each sample using the Rn-emanation method. The precision (1 σ) based on triplicate analyses averages about ±2.5%. Waters all around the Antarctic continent below 2 km depth appear to exhibit a uniform²²⁶Ra concentration of 21.5 ± 1dpm/100kg, except perhaps locally such as the Ross Sea and the Drake Passage where small variations may be present. Higher in the water column, the²²⁶Ra contents decrease toward the surface with gradients which vary as a function of the influence exerted by the Antarctic Convergence. Across this oceanic front, a north-to-south increase of²²⁶Ra occurs (the increase being the largest near the surface: from 8 to 18 dpm/100 kg), reflecting the combining effect of deep-water upwelling and meridional water mixing. The core layer of the Antarctic Intermediate Water contains about 14 dpm/100 kg of²²⁶Ra and that of the Circumpolar Intermediate Water (O₂ minimum and local T maximum) about 18 dpm/100 kg. To a first approximation,²²⁶Ra covaries with Si in the circumpolar waters.     

Ra in the Japan Sea and the residence time of the Japan Sea water

The surface water of the Japan Sea contained²²⁶Ra of70 ± 4dpm m⁻³ which was nearly equal to that of the surface water in the North Pacific. The concentration of²²⁶Ra in the Japan Sea deep water below 500 m was151 ± 8dpm m⁻³, showing a vertically and regionally small variation. This concentration of²²⁶Ra in the deep water is unexpectedly high, because the Japan Sea deep water has a higher Δ¹⁴ C value by about 50‰ than the Atlantic deep water containing the same²²⁶Ra. One of the causes to be considered is larger contribution of²²⁶Ra from biogenic particles dissolving in the Japan Sea deep water, but the Japan Sea is not so fertile in comparison to the Bering Sea. The other more plausible cause is the internal ventilation of the Japan Sea water, which means that the residence time of the Japan Sea Proper water is considerably long although the water is vertically mixed fairly well especially in winter. The ventilation may supply some amounts of radiocarbon and oxygen but does not change the inventory of²²⁶Ra. The residence times of the Japan Sea deep water and of water within the Japan Sea are calculated by solving simultaneous equations for²²⁶Ra and¹⁴C with a three-box model to be 300–400 years and 700–1000 years, respectively.     

Increased zooplankton PAH concentrations across hydrographic fronts in the East China Sea

The Changjiang has transported large quantities of polycyclic aromatic hydrocarbons (PAHs) to the East China Sea (ECS), but information of these pollutants in zooplankton is limited. To understand PAHs pollution in zooplankton in the ECS, total concentrations of PAHs in zooplankton from surface waters were measured. Values of PAHs ranged from 2 to 3500 ng m⁻³ in the ECS, with highest PAHs levels located at the salinity front between the Changjiang Diluted Water (CDW) and the mid-shelf waters. In contrast, concentrations of zooplankton PAHs in the mid-shelf and outer-shelf waters were significantly lower (2–23 ng m⁻³) than those in the CDW. These results demonstrate that PAHs are conspicuously accumulated in zooplankton at the salinity front between the CDW and the mid-shelf waters. These higher levels of PAHs in zooplankton at the salinity front may be further biomagnified in marine organisms of higher trophic levels through their feeding activities.     

Distribution of <Superscript>226</Superscript>Ra in the Arctic Ocean and the Bering Sea and its hydrologic implications

Radium-226 (²²⁶Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Expedition. The results showed that ²²⁶Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m³ with an average of 0.76 Bq/m³ in the Arctic Ocean, and from 0.25 to 1.26 Bq/m³ with an average of 0.71 Bq/m³ in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that the study area may be partly influenced by sea ice meltwater. In the Bering Sea, ²²⁶Ra in the surface water decreased northward, probably as a result of the exchange between the ²²⁶Ra-deficient sea ice meltwater and the ²²⁶Ra-rich Pacific water. In the Arctic Ocean, ²²⁶Ra in the surface water increased northward and eastward. This spatial distribution of ²²⁶Ra reflected the variation of the ²²⁶Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of ²²⁶Ra in the Canadian Basin showed a concentration maximum at 200 m, which could be attributed to the inputs of the Pacific water or/and the bottom shelf water with high ²²⁶Ra concentration. This conclusion was consistent with the results from ²H, ¹⁸O tracers.     

226Ra and210Pb in the Weddell Sea

²²⁶Ra and²¹⁰Pb were measured in sections and profiles collected in the Weddell Sea during the International Weddell Sea Oceanographic Expedition in 1973. The results can be correlated with the circulation and mixing schemes deduced from hydrographic observations. Along the surface cyclonic gyre the Ra activities are fairly uniform at about 17 dpm/100 kg, quite similar to those of the Circumpolar surface water south of the Antarctic Convergence. The²¹⁰Pb activities in the northern flank of the gyre, probably influenced by the high²¹⁰Pb-bearing Circumpolar Deep Water in the north, are as high as 12 dpm/100 kg. At the central gyre and its southern flank, the surface water²¹⁰Pb activities are about 7 dpm/100 kg. The warmer surface water at the central gyre has a Ra activity of about 19 dpm/100 kg, slightly higher than the colder surface water at the flanks. Thus lower²¹⁰Pb/²²⁶Ra activity ratios are observed in the central gyre, and higher ratios in its flanks. Similar relationships between Ra and Pb are noted in the Weddell Sea Bottom Water (WSBW): lower Pb associated with higher Ra in the center; higher Pb with slightly lower Ra in the flanks.Vertical profiles along the cyclonic gyre show lower Ra and Pb activities in the southwestern Weddell Basin where lower temperature and lower silicate are observed. Similar to Ba, both Ra and Si are non-conservative in the Weddell Sea, with significant input from the bottom sediments and particulate dissolution during subsurface mixing.Each water mass or type in the Weddell Sea is well characterized by its Ra content, but not well by its Pb content. Ra and Si are crudely correlated with a slope of about 7 × 10^?4 dpm Ra per μmole of Si. The fact that the WSBW values fall on the slope suggests that the net input rate for Ra (corrected for the decay rate) is proportional to that of Si. The linear extrapolation to zero Si gives a Ra value of 13 dpm/100 kg. These relationships are quite similar to those observed in the Circumpolar waters.     

210Pb and226Ra distributions in the Circumpolar waters

²¹⁰Pb and²²⁶Ra profiles have been measured at five GEOSECS stations in the Circumpolar region. These profiles show that²²⁶Ra is quite uniformly distributed throughout the Circumpolar region, with slightly lower activities in surface waters, while²¹⁰Pb varies with depth as well as location or area. There is a subsurface²¹⁰Pb maximum which matches the oxygen minimum in depth and roughly correlates with the temperature and salinity maxima. This²¹⁰Pb maximum has its highest concentrations in the Atlantic sector and appears to originate near the South Sandwich Islands northeast of the Weddell Sea. Concentrations in this maximum decrease toward the Indian Ocean sector and then become fairly constant along the easterly Circumpolar Current.Relative to²²⁶Ra, the activity of²¹⁰Pb is deficient in the entire water column of the Circumpolar waters. The deficiency increases from the depth of the²¹⁰Pb maximum toward the bottom, and the²¹⁰Pb/²²⁶Ra activity ratio is lowest in the Antarctic Bottom Water, indicating a rapid removal of Pb by particulate scavenging in the bottom layer and/or a short mean residence time of the Antarctic Bottom Water in the Circumpolar region.²²⁶Ra is essentially linearly correlated with silica and barium in the Circumpolar waters. However, close examination of the vertical profiles reveals that Ba and Si are more variable than²²⁶Ra in this region.     

An integrated East China Sea–Changjiang Estuary model system with aim at resolving multi-scale regional–shelf–estuarine dynamics

A high-resolution numerical model system is essential to resolve multi-scale coastal ocean dynamics. So a multi-scale unstructured grid-based finite-volume coastal ocean model (FVCOM) system has been established for the East China Sea and Changjiang Estuary (ECS–CE) with the aim at resolving coastal ocean dynamics and understanding different physical processes. The modeling system consists of a three-domain-nested weather research and forecasting model, FVCOM model with the inclusion of FVCOM surface wave model in order to understand the wave–current interactions. The ECS–CE system contains three different scale models: a shelf-scale model for the East China Sea, an estuarine-scale model for the Changjiang Estuary and adjacent region, and a fine-scale model for the deep waterway regions. These three FVCOM-based models guarantee the conservation of mass and momentum transferring from outer domain to inner domain using the one-way common-grid nesting procedure. The model system has been validated using data from various observation data, including surface wind, tides, currents, salinity, and wave to accurately reveal the multi-scale dynamics of the East China Sea and Changjiang Estuary. This modeling system has been demonstrated via application to the seasonal variations of Changjiang diluted water and the bottom saltwater intrusion in the North Passage, and it shows strong potential for estuarine and coastal ocean dynamics and operational forecasting.     

Yangtze- and Taiwan-derived sediments on the inner shelf of East China Sea

X-ray diffraction (XRD) mineralogical and grain-size analyses indicate that inner continental shelf sediments in the East China Sea (ECS) represent a unique mixing of clays derived from the Yangtze River and silts/sands from small western Taiwanese rivers. Taiwanese (e.g., Choshui) clays (<2 μm) display no smectite but the best illite crystallinity and are only distributed along southeastern Taiwan Strait. Both Yangtze and Taiwanese river clays are illite-dominated, but the poor illite crystallinity and the presence of smectite and kaolinite indicate that Taiwan Strait clays are mainly Yangtze-dominated. In contrast, medium silts (20–35 μm) and very fine sands (63–90 μm) in the Taiwan Strait are characterized by low feldspar/quartz, low K-feldspar/plagioclase and high kaolinite/quartz, indicating their provenance from Taiwanese rivers. Taiwanese silts and sands are introduced primarily by the way of typhoon-derived floods and transported northward by the Taiwan Warm Current during summer–fall months. Yangtze clays, in contrast, are widely dispersed southward about 1000 km to the western Taiwan Strait, transported by the China Coastal Current during winter–spring months. Since most Taiwan Strait samples were collected in May 2006, clay results in this paper might only represent the winter–spring pattern of the dispersal of Yangtze sediments.     

Biweekly periodic variation of the Kuroshio axis northeast of Taiwan as revealed by ocean high-frequency radar

An analysis of surface current data obtained from 2002 to 2005 using long-range high-frequency radar provides the first evidence for the presence of biweekly (11–14 day) periodic variations of the Kuroshio axis northeast of Taiwan. This analysis clarifies the spatiotemporal characteristics of these variations and reveals that cyclonic/anticyclonic eddies propagating along the shelf slope from the vicinity of the deep channel east of Taiwan induce these variations northeast of Taiwan. The behavior of the cyclonic/anticyclonic eddies on the shelf slope is well explained by 2nd-mode interior shelf waves advected by the Kuroshio's mean flow. Remote effects from the vicinity of the deep channel east of Taiwan, or from outside the East China Sea, are believed to play an important role in the generation of these biweekly periodic variations of the Kuroshio axis northeast of Taiwan. Moreover, on the shelf slope, these variations cause an onshore current across the shelf slope, suggesting topographically controlled upwelling. Therefore, the biweekly periodic variations of the Kuroshio axis northeast of Taiwan might contribute not only to the onshore transport of Kuroshio surface water but also to transport nutrient-rich Kuroshio subsurface water onto the shelf in the East China Sea.     

The intrinsic nonlinear multiscale interactions among the mean flow,low frequency variability and mesoscale eddies in the Kuroshio region

Using a new functional analysis tool, multiscale window transform(MWT), and the MWT-based localized multiscale energetics analysis and canonical transfer theory, this study reconstructs the Kuroshio system on three scale windows, namely,the mean flow window, the interannual-scale(low-frequency) window, and the transient eddy window, and investigates the climatological characteristics of the intricate nonlinear interactions among these windows. Significant upscale energy transfer is observed east of Taiwan, where the mean Kuroshio current extracts kinetic energy from both the interannual and eddy windows.It is found that the canonical transfer from the interannual variability is an intrinsic source that drives the eddy activities in this region. The multiscale variabilities of the Kuroshio in the East China Sea(ECS) are mainly controlled by the interaction between the mean flow and the eddies.The mean flow undergoes mixed instabilities(i.e., both barotropic and baroclinic instabilities) in the southern ECS, while it is barotropically stable but baroclinically unstable to the north. The multiscale interactions are found to be most intense south of Japan, where strong mixed instabilities occur; both the canonical transfers from the mean flow and the interannual scale are important mechanisms to fuel the eddies. It is also found that the interannual-scale energy mainly comes from the barotropically unstable jet, rather than the upscale energy transfer from the high frequency eddies.     

Pb in the western Indian Ocean: distribution, disequilibrium, and partitioning between dissolved and particulate phases

²²⁶Ra profiles have been measured in the western Indian Ocean as part of the 1977–1978 Indian Ocean GEOSECS program. These profiles show a general increase in deep and bottom water Ra concentration from the Circumpolar region to the Arabian Sea. A deep Ra maximum which originates in the Arabian Sea and in the Somali basin at about 3000 m depth spreads southward into the Mascarene basin and remains discernible in the Madagascar and Crozet basins. In the western Indian Ocean, the cold Antarctic Bottom Water spreads northward under the possibly southward-flowing deep water, forming a clear benthic front along the Crozet basin across the Southwest Indian Ridge into the Madagascar and Mascarene basins. The Antarctic Bottom Water continues to spread farther north to the Somali basin through the Amirante Passage at 10°S as a western boundary current. The benthic front and other characteristic features in the western Indian Ocean are quite similar to those observed in the western Pacific where the benthic front as a distinctive feature was first described by Craig et al. [15]. Across the Mid-Indian Ridge toward the Ceylon abyssal plain near the triple junction, Ra profiles display a layered structure, reflecting the topographic effect of the mid-ocean ridge system on the mixing and circulation of the deep and bottom waters. Both Ra and Si show a deep maximum north of the Madagascar basin. Linear relationships between these two elements are observed in the deep and bottom water with slopes increasing northward. This suggests a preferential input of Ra over Si from the bottom sediments of the Arabian Sea and also from the flank sediments of the Somali basin.     

Effect of the mesoscale hydrographic features on larval fish distribution across the shelf break of East China Sea

Surveys of fish larvae and oceanographic conditions were conducted along transects across the shelf break region in the East China Sea (ECS) in May 2001. The objective of this study was to investigate the distribution and assemblages of fish larvae across the shelf break region and their relationships to mesoscale hydrographic features. There was a warm surface streamer from the Kuroshio which extended toward the shelf region of the ECS; concurrently, we observed the intrusion of the less saline shelf water into the subsurface layer towards the offshore. In all 66 taxa (65 families and 1 order) of larvae were collected by oblique net tows using a bongo net, the larval fish density and number of families sampled were lower in the low-temperature area. Based on cluster analysis and environmental factor, two larval fish assemblages were identified: off-shelf/Kuroshio and shelf break. In shelf break assemblage, Auxis spp. and Diaphus spp. were abundant in the warm surface streamer. In contrast, Maurolicus japonicus, Synagrops spp., Bregmaceros sp. and Champsodon spp. were found in the off-shelf region where the offshore intrusion of less-saline water occurred. This different pattern of the horizontal distribution would reflect vertical distribution of the larvae in the water column. Moreover, copepod nauplii density was higher in the upper layer of the shelf region. Thus, dynamic interactions between the Kuroshio and shelf waters at the frontal boundary are concluded to potentially affect larval fish transport and prey availability.     

The distribution of 226Ra in the Atlantic Ocean

Based on results obtained during the GEOSECS program the primary features of the distribution of²²⁶Ra in the Atlantic Ocean can be defined. Outside the Antarctic no significant variation has been found in the²²⁶Ra content of surface waters. Eighty samples yield an average of 7.4 dpm/100 kg (normalized to a salinity of 35.00‰). Deep waters in the central Atlantic have²²⁶Ra contents several dpm/100 kg higher than expected from the mixing of Antarctic Bottom Water (21.3 dpm/100 kg) and basal North Atlantic Deep Water (10.3 dpm/100 kg). These excesses correlate well with deficiencies in O₂ and excesses in SiO₂. The intermediate water²²⁶Ra maximum in the South Atlantic is associated with the inflow of low-oxygen Circumpolar Intermediate Water beneath the Antarctic Intermediate Water.     

Radium in the near-surface Caribbean Sea

Recent radium measurements from the near-surface Caribbean Sea are presented. The surface horizontal and vertical distributions of²²⁶Ra are essentially the same as reported by Szabo et al. (1967) for the early 1960's. The²²⁶Ra activity at the surface is relatively uniform across the Caribbean, with an average of8.2±0.4dpm/100kg. The subsurface distribution to ～200 m averages7.8±0.4dpm/100kg and increases slowly below 200 m. reaching ～9.5 dpm/100 kg at 560 m. In contrast to²²⁶Ra, the surface concentration of²²⁸Ra was much more variable in both time and space. An average increase of 33% was found between 1968 and 1976 in the western Caribbean and during both years an anomalously high²²⁸Ra activity was found in the eastern Caribbean. These data support previous hypotheses that water entering the eastern Caribbean has been enriched in²²⁸Ra prior to entry and that variable mixing of the Atlantic water masses found to the northeast and southeast of the Lesser Antilles may produce temporal variations in the near-surface²²⁸Ra activity. Scatter plots of²²⁸Ra vs. salinity and sigma-t indicate that the near-surface vertical distribution of²²⁸Ra in the Caribbean Sea is predominantly influenced by advection. Thus²²⁸Ra cannot be used to study near-surface vertical mixing rates in this region.     

Radium isotopes in sub-Arctic waters

Measurements of the²²⁸Ra/²²⁶Ra activity ratio in the waters of the Greenland, Norwegian and Labrador Seas and Baffin Bay reveal strong horizontal gradients in the surface waters. The coastal waters are dominated by²²⁸Ra injection from nearshore sediments. There is an inverse correlation between the²²⁸Ra/²²⁶Ra activity ratio and salinity in the 30–36‰ salinity range. Vertical profiles indicate that the²²⁸Ra/²²⁶Ra activity ratio is also strongly coupled toσ_θ except for some regions where²²⁸Ra is being injected into higher density water as these isopycnals intersect coastal areas. We use these measurements in the area of formation of North Atlantic Deep Water to estimate that this water mass forms with a²²⁸Ra/²²⁶Ra activity ratio of 0.10.     

Temporal variation of228Ra in the near-surface Gulf of Mexico

The Mn-fiber technique for extracting radium from seawater has proved useful for studying the marine geochemistry of²²⁸Ra. In the Gulf of Mexico, this technique was used to measure the surface and near-surface distribution of²²⁶Ra and²²⁸Ra. The observed surface distribution of²²⁸Ra, and particularly the radium activity ratio (228/226) can be explained by known circulation patterns, or, when local surface currents are not well understood, may provide insight into their general characteristics.The radium activity ratio has increased from 0.5 in 1968 to 0.7 in 1973 in the surface Gulf of Mexico. This observed increase cannot be attributed to known anthropogenic or natural source perturbations within the Caribbean Sea-Gulf of Mexico system. Possible causes include a change in the residence time for near-surface water, or variations in the relative dominance of the two sources for water entering the eastern Caribbean; the North Equatorial Current and the Guiana Current.The temporal distribution of²²⁸Ra is unstable and naturally variable over a time period less than or equal to five years in the Gulf of Mexico and by extrapolation, the Caribbean Sea. Therefore, its usefulness in calculations of eddy diffusion coefficients for these regions is greatly diminished.     

Impacts of the Kuroshio intrusion on the two eddies in the northern South China Sea in late spring 2016

During mid-May to early June 2016, a cold eddy and a warm eddy were captured on the continental slope of the northern South China Sea by the in situ measurements. A salty lens-shaped water mass in the subsurface layer existed in these two detected eddies, which indicated they had a Kuroshio water origin. The trajectories of the observed eddies from satellite altimeter data show that the cold eddy was generated in the central part of the Luzon Strait, while the warm eddy was formed southwest of Taiwan. The genesis of the cold eddy is related to a weak Kuroshio loop current, while that of the warm eddy is associated with a strong Kuroshio loop current. The warm eddy east of the Luzon Strait may trigger the Kuroshio from a leaping path to a looping path. During the evolution of these detected eddies, they had interactions with the Kuroshio and Luzon Gyre. Energy analysis from ocean reanalysis data showed that the baroclinic conversion between the cold eddy and the Kuroshio was stronger than that between the cold eddy and Luzon Gyre. During the eddy shedding stage, the warm eddy mainly acquired energy from the Kuroshio loop current through the baroclinic conversion.