Surface Chlorophyll-A Fronts in the Yellow and Bohai Seas Based on Satellite Data

Abstract

Chlorophyll fronts are important to monitor and map the oceanic front, especially in the season when sea surface temperature (SST) fronts weaken. In this study, surface chlorophyll-a (chl-a) fronts in the Yellow and Bohai seas were characterized for the first time using satellite data. Five distinct chl-a fronts (i.e., the Bohai Strait, Shandong Peninsula, Jiangsu, Liaodong Peninsula, and Korean Peninsula fronts) were observed in summer along the 40 m isobaths and faded in other seasons. Notably, these fronts coincided with SST fronts. Strong chl-a fronts emerged during summer due to chl-a blooms in eutrophic coastal waters paired with surface chl-a fading in strongly stratified offshore waters and coastal physical fronts. Although SST fronts were strong during winter, light limitation and strong vertical mixing in offshore waters led to low chl-a in both coastal and offshore waters, suppressing chl-a front formation. Both chl-a and SST fronts coincided with steep seabed slopes (slope ratio > 1), suggesting that seabed slope may be an indicator of oceanic front location.

The Influence of Ocean Processes on Fine-Scale Changes in the Yellow Sea Cold Water Mass Boundary Area Structure Based on Acoustic Observations

“…A more intuitive manifestation of this is the tidal mixing of cold water from deeper layers to the upper layers, resulting in a decrease in SST and, thus, the surface cold patches (SCPs) observable on satellite remote sensing maps (Figure 10a). This has also been confirmed by historical observations [67]. In essence, the upwelling of the YS is caused by strong tidal mixing over the sloping topography.…”

Spatial and Temporal Characteristics of Winter Diel Vertical Migration of Zooplankton and Nekton in the East China Shelf Seas Based on Multi‐Frequency Echosounder

“…However, in the BHS, the relatively low temperature, high turbidity, and shallow water depth might be responsible for the weak unobserved migration. In particular, the area with chl‐a difference of 0 value generally matches the location of winter current fronts(Xia et al., 2021). In general, the moon phase affects the night aggregation layer depth, regardless of GB or FL species, which seems to be a trade‐off between foraging and predator avoidance.…”