1. Off‐Coast Phytoplankton Bloom in the Taiwan Strait During the Northeasterly Monsoon Wind Relaxation Period.
- Author
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Zhao, Zhonghua, Oey, Lie‐Yauw, Huang, Bangqin, Lu, Wenfang, and Jiang, Yuwu
- Subjects
ALGAL blooms ,MONSOONS ,STRAITS ,BAROCLINICITY ,MIXING height (Atmospheric chemistry) ,SELF-organizing maps - Abstract
This study applied cruise, model, and satellite data to analyze the off‐coast phytoplankton blooming during the late fall to early spring monsoon period in the Taiwan Strait when northeasterly wind prevails. Based on the composite and self‐organizing map analyses, the three data sets consistently show high chlorophyll‐a concentration near the along‐shore front during the down‐front northeasterly wind relaxation period while lower concentration when relatively strong wind is persistent. Meanwhile, the off‐coast blooming always coincides with intense near‐surface stratification when the northeasterly wind relaxes. Diagnoses of balanced Richardson number, Ertel potential vorticity and instability energy budget from high‐resolution cruise observations and model results demonstrate that vigorous submesoscale symmetric and baroclinic instabilities can develop near the along‐shore front under the down‐front NE wind. Diagnoses of modeled buoyancy and chlorophyll‐a budget equations further suggest the submesoscale instabilities lead to rapid near‐surface restratification and offshore stretching of the along‐shore front within the upper 10‐m of the mixed layer when the down‐front NE wind relaxes, favoring the surface 10‐m phytoplankton growth. As comparison, contribution of the larger‐scale advection related with geostrophic adjustment and Ekman transport to the chlorophyll‐a increment reached beyond the middle layer of ∼20‐m depth. Plain Language Summary: Cruise and satellite observations presented three phytoplankton growth scenarios depending on dominant wind characteristics from winter to early spring in the Taiwan Strait. Off‐coast blooms with significantly higher chlorophyll‐a concentration were observed during the northeasterly monsoon relaxation period compared with persistent northeasterly wind or southwesterly wind periods. High‐resolution cruise and model results indicate that submesoscale instability‐induced near‐surface restratification near the coastal front along mainland China's coast triggers the off‐coast bloom. This study has practical significances on harmful algal bloom prediction and fishery development near coastal waters. Key Points: Multi‐source observations confirm the significant growth of phytoplankton during the northeasterly monsoon relaxation in the Taiwan Strait (TWS)High‐resolution cruise and model results show vigorous submesoscale instabilities near the along‐shore front during bloomingInstability‐induced restratification primarily favors off‐coast phytoplankton growth within the upper 10‐m of the mixed layer [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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