Monitoring of the Changjiang River Plume in the East China Sea using a Wave Glider

Moh, Taejun; Cho, Jin Hyung; Jung, Seom‐Kyu; Kim, Sang-Hyun; Son, Young Baek

doi:10.2112/si85-006.1

Cited by 8 publications

(19 citation statements)

References 12 publications

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“…Since detection of low salinity water mass is important, the network was trained and validated with as many relatively low salinity conditions as possible. In the summer of 2016, a large amount of freshwater from the Changjiang River plume was observed [9,13,41]. Therefore, the year 2016 was selected as a study period when relatively low SSS covered wide regions in the ECS.…”

Section: Mpnnmentioning

confidence: 99%

Estimation of Hourly Sea Surface Salinity in the East China Sea Using Geostationary Ocean Color Imager Measurements

et al. 2020

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Sea surface salinity (SSS) is an important tracer for monitoring the Changjiang Diluted Water (CDW) extension into Korean coastal regions; however, observing the SSS distribution in near real time is a difficult task. In this study, SSS detection algorithm was developed based on the ocean color measurements by Geostationary Ocean Color Imager (GOCI) in high spatial and temporal resolution using multilayer perceptron neural network (MPNN). Among the various combinations of input parameters, combinations with three to six bands of GOCI remote sensing reflectance (Rrs), sea surface temperature (SST), longitude, and latitude were most appropriate for estimating the SSS. According to model validations with the Soil Moisture Active Passive (SMAP) and Ieodo Ocean Research Station (I-ORS) SSS measurements, the coefficient of determination (R2) were 0.81 and 0.92 and the root mean square errors (RMSEs) were 1.30 psu and 0.30 psu, respectively. In addition, a sensitivity analysis revealed the importance of SST and the red-wavelength spectral signal for estimating the SSS. Finally, hourly estimated SSS images were used to illustrate the hourly CDW distribution. With the model developed in this study, the near real-time SSS distribution in the East China Sea (ECS) can be monitored using GOCI and SST data.

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Section: Mpnnmentioning

confidence: 99%

Estimation of Hourly Sea Surface Salinity in the East China Sea Using Geostationary Ocean Color Imager Measurements

et al. 2020

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“…We investigated the hourly variations in SSS profiles along line AA' in Figure 4 and found that SSS values decreased over time (Figure 5). The SSS values ranged from 25 to 28 psu along the line and the average values at each GOCI acquisition time in Figure 5 from wave-glider time-series data according to the tidal status have not been found [19]. We investigated the hourly variations in SSS profiles along line AA' in Figure 4 and found that SSS values decreased over time (Figure 5).…”

Section: Temporal Variationsmentioning

confidence: 99%

“…We collected in situ salinity data in the study area when there were strong influences from Changjiang Diluted Water in the East China Sea using a wave glider equipped with a modular low-power conductivity-temperature-depth (CTD) profiler for an autonomous glider (GPCTD; Sea-Bird Scientific, Bellevue, WA, USA). The CTD profiler was installed on the subsurface rudder to measure the surface salinity along with temperature [19] (Figure 1). A total of 501 measurements were obtained in August 2016 from the surface water (depth above ~8 m; ranged from 25.69 to 33.83 psu, with an average of 28.68 psu), with 73 measurements matched to GOCI Rrs products.…”

Section: In Situ Measurementsmentioning

confidence: 99%

“…The Changjiang Diluted Water is like a lens shape or patchlike structure and is response to external forcing such as wind, tidal forcing and river discharge in the East China Sea [1]. However, diurnal variations in salinity from wave-glider time-series data according to the tidal status have not been found [19]. We investigated the hourly variations in SSS profiles along line AA' in Figure 4 and found that SSS values decreased over time (Figure 5).…”

Section: Temporal Variationsmentioning

confidence: 99%

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The Applicability of the Geostationary Ocean Color Imager to the Mapping of Sea Surface Salinity in the East China Sea

et al. 2021

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During the summer season, low-salinity water (LSW) inputs from the Changjiang River are observed as filamentous or lens-like features in the East China Sea. Sea surface salinity (SSS) is an important factor in ocean science, and is used to estimate oceanic carbon fluxes, trace red tides, and calculate other physical processes at the surface. In this study, a proxy was developed using remote sensing reflectance (Rrs) from the Geostationary Ocean Color Imager (GOCI) centered at 490 nm (band 3), 555 nm (band 4), 660 nm (band 5), and 680 nm (band 6), and salinity (data from summer cruises during the period of 2011–2016). It was then validated to map LSW plumes in the East China Sea. The GOCI-derived surface salinity was determined by the empirical relationships between Rrs at the four bands and in situ wave glider SSS data (August 2016), and was validated with synchronous in situ hydrographic SSS data (August 2011, 2012, 2013, and 2016). The GOCI-derived SSS was considered reliable in terms of the validation with the in situ measurement with a high coefficient of determination along with a low RMSE (R2 = 0.803, RMSE = 0.914, N = 21), and in comparisons with two previous models that were used to derive SSS in the East China Sea. The GOCI-derived SSS was successfully used to examine time-series variations on diurnal and daily scales, and the effects of a typhoon in terms of marine physical and biological properties in combination with the chlorophyll-a concentration and sea surface temperature.

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“…In August 1996, the CDW (< 20 psu) passed about 50 km west of Jeju Island, causing widespread death of coastal wildlife (economic damage: US$600 million). In August 2016, abnormally lowsalinity and high sea surface temperature waters were observed along the coast of Jeju Island (Moh et al, 2018;Moon et al, 2019). Anomalous sea surface warming during the summer in the ECS is associated with the dispersion of the CDW, forming a boundary layer that enhances vertical stratification and reduces vertical mixing (Park et al, 2011;Park et al, 2015;Moh et al, 2018;Moon et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Mapping the Changjiang Diluted Water in the East China Sea during summer over a 10-year period using GOCI satellite sensor data

Son

Choi

2022

Front. Mar. Sci.

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The Changjiang River loads freshwater into the East China Sea (ECS) and the Yellow Sea (YS). A low-salinity plume known as Changjiang Diluted Water (CDW) is formed by mixing with saline ambient waters; it disperses toward Jeju Island and the East/Japan Sea due to the dominant southerly wind and tide during summer. To map the offshore surface CDW in the ECS, a proxy was developed using surface water beam attenuation (c) and salinity from 18 annual summer cruises matched with synchronous Geostationary Ocean Color Imager (GOCI) satellite data. We followed a two-step empirical approach. First, a relationship between in situ salinity and c was obtained from hydrographic cruises (1998, 2003–2018, and 2021). Second, in situ c was matched with GOCI remote-sensing reflectance (Rrs) band ratios of all available blue-to-green wavelengths (2011–2018). Finally, satellite-derived surface salinity was determined directly by combining the two empirical relationships, providing a robust estimate over a range of salinities (22–34 psu). Our algorithm was then compared and validated with five previous satellite-derived salinity algorithms based on colored dissolved organic matter and particle concentrations. In the first step, surface salinity was matched and well correlated with c using an 18-year full conductivity–temperature–depth (CTD) dataset (N = 1,345, R2 = 0.93). In the second step, c was synchronously matched and well correlated with GOCI Rrs band ratios using an 8-year summer CTD dataset (N = 391, R2 = 0.93). The satellite-derived surface salinity based on the GOCI was compared with five other approaches and validated using an 8-year summer CTD dataset (2011–2018, N = 707, RMSE = 0.43, bias = 0.053, mean ratio = 1.002). We mapped satellite-derived surface salinity using monthly GOCI images during the summer from 2011 to 2020. The spatial patterns of the CDW were connected to the Changjiang River mouth and extended to the east–northeast during summer. Saline water was confined to the warm current and the upper slope in the eastern part of the study area. Anomalous dispersion of the CDW occurred in August 2016, 2017, and 2020, and limited dispersion occurred in August 2014 and 2019.

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Monitoring of the Changjiang River Plume in the East China Sea using a Wave Glider

Cited by 8 publications

References 12 publications

Estimation of Hourly Sea Surface Salinity in the East China Sea Using Geostationary Ocean Color Imager Measurements

Estimation of Hourly Sea Surface Salinity in the East China Sea Using Geostationary Ocean Color Imager Measurements

The Applicability of the Geostationary Ocean Color Imager to the Mapping of Sea Surface Salinity in the East China Sea

Mapping the Changjiang Diluted Water in the East China Sea during summer over a 10-year period using GOCI satellite sensor data

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