Advances on Coastal and Estuarine Circulations Around the Changjiang Estuary in the Recent Decades (2000–2020)

Abstract

Advances on the circulation in the Changjiang Estuary and adjacent East China Sea (ECS) and Yellow Sea (YS) coastal waters in the recent decades (2000–2020) are synthesized in this review. The circulation over the complicated bathymetry in the region is locally driven by winds, tides, as well as riverine discharge, and is remotely influenced by shelf currents between the 50 and 100-m isobaths through the cross-shelf exchanges. The interchange of the momentum and the freshwater pathway inside the Changjiang Estuary are jointly determined by tides and seasonally varying discharge and winds over the shelf. The buoyant waters are trapped inside the bulge that forms and expands over the shelf to the west of the 30-m isobath in the vicinity of Hangzhou Bay and the Changjiang Estuary. These buoyant waters are exported offshore by the shelf current, tidal mixing, and variations of wind patterns, forming the Changjiang River plume, which shows notable seasonality due to the reversal of both winds and shelf currents in the ECS and YS. Extensive spatial irregularities in the form of freshwater patches are present along its pathway to the Tsushima Strait in summer and to the Taiwan Strait in winter, respectively. Tides and the bathymetry irregularity have recently been found to play critical roles in determining the cross-shelf exchanges of water mass and momentum along the pathway of the ECS coastal current, and along this pathway, a year-round upslope intrusion of shelf waters appears in both summer and winter. Tides also play an important role in altering the expansion of the Changjiang River plume, cross-shelf extrusion of waters, and variation in the Yellow Sea Coastal Current over the shallow Subei Shoal.

Role of phosphorus in the seasonal deoxygenation of the East China Sea shelf

“…The resulting P limitation in offshore waters expanded to Jeju Island in the northeast at the seasonal peak of the plume expansion (Figure 5). This large-scale distribution of surface nutrients and their limitation effect on primary production are consistent with the main seasonal circulation (Bai et al, 2014;Liu et al, 2021), with observations off the CE (Li et al, 2009;Wang et al, 2015), as well as with observations of Changjiang-related excess NO3 in the northeastern ECS (Wong et al, 1998) and near Jeju Island (Kodama et al, 2017;Moon et al, 2021). Despite its large-scale distribution, P limitation was most prominent over the southwestern part of the Yangtze Bank (Figure 4) from mid-July to early August (Figure 6), i.e., around the peak of the discharge.…”

“…For instance, in the somewhat similar Mississippi River plume in the northern Gulf of Mexico, seasonal P limitation is observed around mid-shelf at the peak of annual production, between a light limited area in the vicinity of the river and the N-limited downstream/offshore waters (Laurent et al, 2012;Sylvan et al, 2006). Phytoplankton growth limitation in the ECS followed these general patterns along the CE-JI transect, but over a larger spatial scale given the dispersive nature of the Changjiang plume (Liu et al, 2021).…”

Changjiang Delta in the Anthropocene: Multi-scale hydro-morphodynamics and management challenges

“…The shelf currents play a role in modulating the river plume and seaward sediment dispersion (Liu et al, 2021). To the north of the CD, the Subei Currents are perennially southward, which can drive sediment transport from the abandoned Yellow River delta towards the CD, supplying sediment in building up the northern delta plains (Wang et al, 2020;Shang et al, 2021), even to the depocenter zone (Liu et al, 2010b).…”

Interpretation of Subsurface Salinity EOFs on Southern ECS Shelf Using SODA Reanalysis: Large‐Scale Patterns and Seasonal to Interannual Variations

“…The Changjiang runoff is the largest discharge into the ECS shelf ocean and cannot be neglected in the role of the formation of low‐salinity shelf water. Observations frequently showed a patchlike structure of the low‐salinity water detached from the Changjiang Diluted Water (CDW) plume (Gao et al., 1992; Liu et al., 2021b; Moon et al., 2010; Zhu et al., 1998). Isobe et al.…”

“…The Changjiang runoff is the largest discharge into the ECS shelf ocean and cannot be neglected in the role of the formation of low-salinity shelf water. Observations frequently showed a patchlike structure of the low-salinity water detached from the Changjiang Diluted Water (CDW) plume (Gao et al, 1992;Liu et al, 2021b;Moon et al, 2010;Zhu et al, 1998). Isobe et al (2004) suggested that the isopycnal surface of 24.5 𝐴𝐴 𝐴𝐴𝜃𝜃 may be the deepest layer of the Kuroshio isopycnals outcropping to the sea surface onto the ECS shelf in spring.…”