Abstract
Luzon Strait is the main channel connecting the South China Sea (SCS) and the western Pacific, with complex atmospheric and oceanic dynamic processes. Based on 44 days of glider measurements and satellite observations, we investigated the temporal and vertical variations of chlorophyll-a (Chl-a) concentration in the Luzon Strait from July 25 to September 6, 2019. The Chl a was mainly distributed above 200 m and concentrated in the subsurface chlorophyll maximum (SCM) layer. The depth of SCM ranged between 50 m and 110 m, and the magnitude of SCM varied from 0.42 mg/m3 to 1.12 mg/m3. The variation of Chl a was identified with three stages responding to different dynamic processes. Under the influence of Kuroshio intrusion, the SCM depth sharply deepened, and its magnitude decreased in Stage 1. Afterward, a prominent Chl-a bloom was observed in the SCM layer from August 6 to August 16. The Chl-a bloom in Stage 2 was related to the influence of a cyclonic eddy, which uplifted of the thermocline and thus the deep nutrients. During Stage 3, prolonged heavy rainfall in the northeastern SCS resulted in a significant salinity decrease in the upper ocean. The convergence of upper water deepened the thermocline and the mixed layer. Thus, the Chl a decreased in the SCM layer but increased in the surface layer. In particular, a typhoon passed through the Luzon Strait on August 24, which induced the Chl a increase in the upper 50 m. However, there was little change in the depth-integrated Chl a (0–200 m), indicating that the Chl a increase in the surface layer was likely associated with physical entrainment of SCM caused by strong mixing, rather than the phytoplankton bloom in the upper water column. Underwater gliders provide frequent autonomous observations that help us understand the regional ocean’s complex dynamic processes and biological responses.
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Data Availability Statement
All data generated and/or analyzed during this study are available from the authors upon reasonable request, except for the glider data, which require permission from the South China Sea Special Management Office.
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Acknowledgment
The authors are grateful for the reviewers’ careful review and constructive suggestions to improve the manuscript. The glider data were provided by the South China Sea Institute of Oceanology, Chinese Academy of Sciences. The WOA13 data were obtained from the Asia-Pacific Data Research Center (http://apdrc.soest.hawaii.edu/data). The surface chlorophyll data were downloaded from the NASA’s OceanColor Web (https://oceancolor.gsfc.nasa.gov/l3/). The SLA and absolute geostrophic velocity data were provided by CMEMS (http://marine.copernicus.eu). Rainfall data were retrieved from the Tropical Rainfall Measuring Mission. SSS and 10-m wind data were provided by Remote Sensing Systems (http://www.remss.com/). The TC information was obtained from the China Meteorological Administration (CMA) best track dataset (http://www.tcdata.typhoon.org.cn).
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Supported by the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (No. 2019BT02H594), the Chinese Academy of Sciences (Nos. XDB42010305, XDA15020901, 133244KYSB20190031, SCSIO202201, SCSIO202204), the National Natural Science Foundation of China (No. 41976024), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA13010500), and the Independent Research Project Program of State Key Laboratory of Tropical Oceanography (No. LTOZZ2101)
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Wang, X., Du, Y., Zhang, Y. et al. Effects of multiple dynamic processes on chlorophyll variation in the Luzon Strait in summer 2019 based on glider observation. J. Ocean. Limnol. 41, 469–481 (2023). https://doi.org/10.1007/s00343-022-1416-7
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DOI: https://doi.org/10.1007/s00343-022-1416-7