scholarly journals Energy Sources Generation and Energy Cascades along the Kuroshio East of Taiwan Island and the East China Sea

2021 ◽  
Vol 9 (7) ◽  
pp. 692
Author(s):  
Ru Wang ◽  
Yijun Hou ◽  
Ze Liu
Keyword(s):  
Energy Source ◽  
State Energy ◽  
Sea Surface ◽  
Energy Sources ◽  
Spectral Energy ◽  
The East China Sea ◽  
Energy Cascades ◽  
Taiwan Island ◽  
The Kuroshio ◽  
Source And Sink

There are multi-spatial-scale ocean dynamic processes in the western boundary current region, so the budget of energy source and sink in the Kuroshio Current area can describe the oceanic energy cycle and transformation more accurately. The slope of the one-dimensional spectral energy density varies between −5/3 and −3 in the wavenumber range of 0.02–0.1 cpkm, indicating an inverse energy cascade in the Kuroshio of Taiwan Island and the East China Sea. According to the steady-state energy evolution, an energy source must be present. The locations of energy sources were identified using the spectral energy transfer calculated by 24 years of Ocean General Circulation Model for the Earth Simulator (OFES) data. At the sea surface, the kinetic energy (KE) sources are mainly within 23.2°–25.6° Nand 28°–29° N at less than 0.02 cpkm and within 23.2°–25° N and 26°–30° N at 0.02–0.1 cpkm. The available potential energy (APE) sources are mainly within 22°–28° N and 28.6°–30° N at less than 0.02 cpkm and within22.6°–24.6° N, 25.4°–28° N and 29.2°–30° N at 0.02–0.1 cpkm. Beneath the sea surface, the energy sources are mainly above 400 m depth. Wind stress and density differences are primarily responsible for the KE and APE sources, respectively. Once an energy source is formed, to maintain a steady state, energy cascades (mainly inverse cascades by calculating spectral energy flux) will be engendered. By calculating the energy flux at 600 m depth, KE changes from inflow (sink) to outflow (source), and the conversion depth of source and sink is 380 m. However, outflow of the APE behaves as the source.

Analysis of Energy Sources along the Kuroshio in the East of Taiwan Island and East China Sea 

2021 ◽  
Author(s):  
Ru Wang ◽  
Yijun Hou ◽  
Ze Liu
Keyword(s):  
Energy Source ◽  
Steady State ◽  
State Energy ◽  
Buoyancy Flux ◽  
Sea Surface ◽  
Energy Sources ◽  
Spectral Energy ◽  
Energy Cascades ◽  
Generation Mechanisms ◽  
The Kuroshio

<p>The locations and generation mechanisms of energy sources in the Kuroshio were analyzed. The slope of the one-dimensional spectral energy density varies between -5/3 and -3 in the wavenumber range of 0.03-0.1 cpkm (wavelengths of approximately 209 to 63 km, respectively), indicating an inverse energy cascade in the Kuroshio; according to the steady-state energy evolution, an energy source which occurs at scale smaller than Rhines scale must be present. By analyzing the wavenumber-frequency spectrum, the period of higher kinetic energy (KE) is about 89-209 days and spatial scale is less than 0.03 cpkm. The locations of energy sources were identified with using the spectral energy transfer calculated by altimetry and model data. At the sea surface, the KE sources are mainly within 23.2°-25.2°N and 28°-30°N at less than 0.03 cpkm and 23.2°-23.6°N and 26°-30°N at 0.03-0.1 cpkm. The available potential energy (APE) sources are mainly within 22.2°-28°N and 28.6°-30°N at less than 0.03 cpkm and 29.2°-30°N at 0.03-0.1 cpkm. Wind stress and density differences (including buoyancy flux, temperature flux and salinity flux) are primarily responsible for the KE and APE sources, respectively. Beneath the sea surface, the energy sources are mainly above 400 m depth, and buoyancy flux plays a major role in the generation of energy sources. The energy cycle process can be summarized as follows: once an energy source is formed, to maintain a steady state, energy cascades (mainly inverse cascades) will be engendered.</p><p> </p>

scholarly journals Rapid warming of sea surface temperature along the Kuroshio and the China coast in the East China Sea during the 20th century

2021 ◽  
pp. 1-43
Author(s):  
Yoshi N. Sasaki ◽  
Chisato Umeda
Keyword(s):  
20Th Century ◽  
East China Sea ◽  
Sea Surface ◽  
East China ◽  
Model Output ◽  
The East China Sea ◽  
China Sea ◽  
Sst Warming ◽  
The Kuroshio ◽  
China Coast

AbstractIt has been reported that the sea surface temperature (SST) trend of the East China Sea during the 20th century was a couple of times larger than the global mean SST trend. However, the detailed spatial structure of the SST trend in the East China Sea and its mechanism have not been understood. The present study examines the SST trend in the East China Sea from 1901 to 2010 using observational data and a Regional Ocean Modeling System (ROMS) with an eddy-resolving horizontal resolution. A comparison among two observational datasets and the model output reveal that enhanced SST warming occurred along the Kuroshio and along the coast of China over the continental shelf. In both regions, the SST trends were the largest in winter. The heat budget analysis using the model output indicates that the upper layer temperature rises in both regions were induced by the trend of ocean advection, which was balanced to the increasing of surface net heat release. In addition, the rapid SST warming along the Kuroshio was induced by the acceleration of the Kuroshio. Sensitivity experiments revealed that this acceleration was likely caused by the negative wind stress curl anomalies over the North Pacific. In contrast, the enhanced SST warming along the China coast resulted from the ocean circulation change over the continental shelf by local atmospheric forcing.

scholarly journals Characteristic Analysis of Sea Surface Currents around Taiwan Island from CODAR Observations

2021 ◽  
Vol 13 (15) ◽  
pp. 3025
Author(s):  
Yu-Hao Tseng ◽  
Ching-Yuan Lu ◽  
Quanan Zheng ◽  
Chung-Ru Ho
Keyword(s):  
Taiwan Strait ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Surface Currents ◽  
Spatiotemporal Resolution ◽  
The North ◽  
Taiwan Island ◽  
The Taiwan Strait ◽  
The Kuroshio ◽  
Kuroshio Region

Sea surface currents observed by high-frequency (HF) radars have been widely used in ocean circulation research. In this study, hourly sea surface currents observed by the Taiwan Coastal Ocean Dynamics Applications Radar (CODAR) system from 2015 to 2019 were analyzed by the empirical orthogonal function (EOF) analysis to reveal the characteristics of the sea surface currents around Taiwan Island. The study area is divided into two regions, the Kuroshio region east of Taiwan Island and the Taiwan Strait west of Taiwan Island. In the Kuroshio region, the first EOF mode shows that the Kuroshio is characterized by higher current speeds with greater variability in summer. The second and third EOF modes present a dipole eddy pair and single eddy impingement on the Kuroshio during different periods. The seasonal variation of the dipole eddy pair indicates that the cyclonic/anticyclonic eddy on the north/south side appears more frequently in summer. Single eddy impingement occurs at multiple periods, including daily, intraseasonal, interseasonal, and annual periods. For the Taiwan Strait, the first EOF mode displays the tide signals. The tides enter the Taiwan Strait from the north and south, forming strong sea surface currents around the northern tip of Taiwan Island and the Penghu Archipelago. The second EOF mode exhibits the seasonal changes of the sea surface currents driven by the monsoon winds. The sea surface currents in the northern Taiwan Strait are relatively strong, possibly due to the narrow and shallow terrain there. The high spatiotemporal resolution of sea surface currents derived from CODAR observations provide more detailed characteristics of sea surface circulation around Taiwan Island.

scholarly journals Radiolarian assemblages in the shelf area of the East China Sea and Yellow Sea and their ecological indication of the Kuroshio Current derivative branches

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9976 ◽  
Author(s):  
Hanxue Qu ◽  
Yong Xu ◽  
Jinbao Wang ◽  
Xin-Zheng Li
Keyword(s):  
East China Sea ◽  
Yellow Sea ◽  
Kuroshio Current ◽  
Sea Surface ◽  
The Yellow Sea ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
The Kuroshio ◽  
Radiolarian Assemblages

We analyzed the radiolarian assemblages of 59 surface sediment samples collected from the Yellow Sea and East China Sea of the northwestern Pacific. In the study region, the Kuroshio Current and its derivative branches exerted a crucial impact on radiolarian composition and distribution. Radiolarians in the Yellow Sea shelf showed a quite low abundance as no tests were found in 15 of 25 Yellow Sea samples. Radiolarians in the East China Sea shelf could be divided into three regional groups: the East China Sea north region group, the East China Sea middle region group, and the East China Sea south region group. The results of the redundancy analysis suggested that the Sea Surface Temperature and Sea Surface Salinity were primary environmental variables explaining species-environment relationship. The gradients of temperature, salinity, and species diversity reflect the powerful influence of the Kuroshio Current in the study area.

scholarly journals Variability of the nutrient stream near Kuroshio's origin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chen-Tung Arthur Chen ◽  
Ting-Hsuan Huang ◽  
Chi-Hsuan Wu ◽  
Haiyan Yang ◽  
Xinyu Guo
Keyword(s):  
Pacific Ocean ◽  
Continental Shelf ◽  
East China Sea ◽  
Kuroshio Extension ◽  
Subsurface Water ◽  
East China ◽  
The East China Sea ◽  
High Productivity ◽  
China Sea ◽  
The Kuroshio

AbstractThe Kuroshio—literally “the Black Stream”—is the most substantial current in the Pacific Ocean. It was called the Black Stream because this oligotrophic current is so nutrient-poor in its euphotic zone that the water appears black without the influence of phytoplankton and the associated, often colored dissolved organic matter. Yet, below the euphotic layer, nutrient concentrations increase with depth while current speed declines. Consequently, a core of maximum nutrient flux, the so-called nutrient stream, develops at a depth of roughly between 200 and 800 m. This poorly studied nutrient stream transports nutrients to and supports high productivity and fisheries on the East China Sea continental shelf; it also transports nutrients to and promotes increased productivity and fisheries in the Kuroshio Extension and the subarctic Pacific Ocean. Three modes of the Kuroshio nutrient stream are detected off SE Taiwan for the first time: one has a single-core; one has two cores that are apparently separated by the ridge at 120.6–122° E, and one has two cores that are separated by a southward flow above the ridge. More importantly, northward nutrient transports seem to have been increasing since 2015 as a result of a 30% increase in subsurface water transport, which began in 2013. Such a nutrient stream supports the Kuroshio's high productivity, such as on the East China Sea continental shelf and in the Kuroshio Extension SE of Japan.

scholarly journals Revisit of a Case Study of Spilled Oil Slicks Caused by the Sanchi Accident (2018) in the East China Sea

2021 ◽  
Vol 9 (3) ◽  
pp. 279
Author(s):  
Zhehao Yang ◽  
Weizeng Shao ◽  
Yuyi Hu ◽  
Qiyan Ji ◽  
Huan Li ◽  
...  
Keyword(s):  
East China Sea ◽  
Oil Spill ◽  
Oil Spills ◽  
Ocean Model ◽  
Sea Surface ◽  
East China ◽  
The East China Sea ◽  
Sar Images ◽  
China Sea ◽  
Spatial Coverage

Marine oil spills occur suddenly and pose a serious threat to ecosystems in coastal waters. Oil spills continuously affect the ocean environment for years. In this study, the oil spill caused by the accident of the Sanchi ship (2018) in the East China Sea was hindcast simulated using the oil particle-tracing method. Sea-surface winds from the European Centre for Medium-Range Weather Forecasts (ECMWF), currents simulated from the Finite-Volume Community Ocean Model (FVCOM), and waves simulated from the Simulating WAves Nearshore (SWAN) were employed as background marine dynamics fields. In particular, the oil spill simulation was compared with the detection from Chinese Gaofen-3 (GF-3) synthetic aperture radar (SAR) images. The validation of the SWAN-simulated significant wave height (SWH) against measurements from the Jason-2 altimeter showed a 0.58 m root mean square error (RMSE) with a 0.93 correlation (COR). Further, the sea-surface current was compared with that from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Version 2 (CFSv2), yielding a 0.08 m/s RMSE and a 0.71 COR. Under these circumstances, we think the model-simulated sea-surface currents and waves are reliable for this work. A hindcast simulation of the tracks of oil slicks spilled from the Sanchi shipwreck was conducted during the period of 14–17 January 2018. It was found that the general track of the simulated oil slicks was consistent with the observations from the collected GF-3 SAR images. However, the details from the GF-3 SAR images were more obvious. The spatial coverage of oil slicks between the SAR-detected and simulated results was about 1 km2. In summary, we conclude that combining numerical simulation and SAR remote sensing is a promising technique for real-time oil spill monitoring and the prediction of oil spreading.

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