Unraveling the Synoptic-Scale Penetration of the Yellow Sea Coastal Water Into the Changjiang River Estuary

As one of the most important coastal currents in the Northeast Pacific marginal seas, the Yellow Sea Coastal Water (YSCW) plays an essential role in modulating regional ocean circulation and the transregional exchange of biogeochemical materials. However, the wintertime transport pattern of the YSCW and its interaction with the Changjiang River Estuary (CJE) are intensely debated. Herein, we used a combination method of Principal Component Analysis-based cluster analysis and Optimum Multiparameter Analysis, together with remote sensing data, to investigate the classification, distributions, pathways and mixture ratios of various water masses off the CJE in winter. Results clearly suggest that in winter the YSCW can repeatedly penetrate to the CJE in response to northerly wind bursts, and flows southward around 10–30 m isobaths off the CJE, with its impact scope reaching as far as at least 29.5°N. Furthermore, we propose a refined circulation pattern that the YSCW flows southward along 20–30 m isobaths on the Changjiang Bank, and thereby feeds the synoptic-scale YSCW penetration into the CJE. Crucially, this work also highlights that the combination methodologies in a mathematic framework is useful for unraveling an implicit synoptic-scale water mass interaction in highly dynamic estuaries and shelf seas, and thus provides better insight to ecological and environmental variability.