Surface drifters released in the central Red Sea during April 2010 detected a well-defined anticyclonic eddy around 23 N. This eddy was 45-60 km in radius, with a swirl speed up to 0.5 m/s. The eddy feature was also evident in monthly averaged sea surface height fields and in current profiles measured on a cross-isobath, shipboard CTD/ADCP survey around that region. The unstructured-grid, Finite-Volume Community Ocean Model (FVCOM) was configured for the Red Sea and process studies were conducted to establish the conditions necessary for the eddy to form and to establish its robustness. The model was capable of reproducing the observed anticyclonic eddy with the same location and size. Diagnosis of model results suggests that the eddy can be formed in a Red Sea that is subject to seasonally varying buoyancy forcing, with no wind, but that its location and structure are significantly altered by wind forcing, initial distribution of water stratification and southward coastal flow from the upstream area. Momentum analysis indicates that the flow field of the eddy was in geostrophic balance, with the baroclinic pressure gradient forcing about the same order of magnitude as the surface pressure gradient forcing.

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Using observations in an applied cruise of the submersible Jiaolong, water characteristics, geostrophic transport, and turbulent mixing in abyssal and hadal zones of the southern Yap Trench were studied. The spatial structures of deep water show that the abyssal water is cold, saline, and oxygen rich. The hadal water has very small changes in potential temperature and potential density, and a little decrease in salinity and obvious decrease in oxygen. The isotherm, isopycnal, and isohaline are depressed in abyss over the central trench. The turbulent mixing is enhanced in the near-bottom zone and the hadal water on the trench slope, especially at the steep slope, the dissipation rate and diff usivity is strong, which weakens the stratifi cation. The geostrophic fl ows move southward in the western region of the trench and northward in the eastern region, indicating cyclonic circulation. In the central region of the trench, the water transport is ~1.74 Sv southward. In the hadal zone, the northward and southward transports are balanced. Our analysis suggests that the abyssal water in the southern Yap Trench is from Lower Circumpolar Water (LCPW) and the hadal water seems to be of the isolated local water rather than LCPW.

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A three-dimension ecological dynamic model was established to numerically study the relationship of HAB and environmental conditions. The numerical experiments showed that the growth of diatom, the dominant HAB specie, was mainly restricted by phosphate and silicate. If the concentrations of phosphate and silicate reach 17-25 µg/L and 300-375 µg/L respectively, the water is in a state of eutrophication. When phosphate and silicate up to 26-32 µg/L and 350-500 µg/L respectively, HAB could be induced. The major regions of HAB occurrence are Jiaozhou Bay mouth, coastal bays, and coastal area from Maidao to Shilaoren. To avoid HAB occurrence, concentration of phosphate and silicate should not exceed 17-20 µg/L and 300 µg/L as a whole. Reasonable control of pollutant discharge is a key point to prevent water eutrophication and HAB occurrence.

This study aims to figure out satellite imaging mechanisms for submerged sand ridges in the shallow water region in the case of the flow parallel to the topography corrugation. Solving the disturbance governing equations of the shear-flow yields the analytical solutions of the secondary circulation. The solutions indicate that a flow with a parabolic horizontal velocity shear and a sinusoidal vertical velocity shear will induce a pair of vortexes with opposite signs distributed symmetrically on the two sides of central line of a rectangular canal. In the case of the presence of surface Ekman layer with the direction of Ekman current opposite to (coincident with) the mean flow, the two vortexes converge (diverge) at the central line of canal in the upper layer and form a surface current convergent (divergent) zone along the central line of the canal. In the case of the absence of surface Ekman layer, there is no convergent (divergent) zone formed over the sea surface. The theoretical results are applied to interpretations of three convergent cases, one divergent case and statistics of 27 cases of satellite observations in the submerged sand ridge region of the Liaodong Shoal in the Bohai Sea. We found that the long, finger-like, bright patterns on SAR images are corresponding to the locations of the canals (or tidal channels) formed by two adjacent sand ridges rather than the sand ridges themselves.Academician Foundation of China; Shanghai Science and Technology Committee Program - Special for EXPO [10DZ0581600]; Shanghai Institute of Urban Ecology and Sustainability [SHUES2011A07]; US National Science Foundation [0962107, 1061998

The Jiangsu Shoal and its adjacent area in the western Yellow Sea (YS) have become hotspots of ecological disasters in China and have attracted considerable attention. Based on remote sensing and field observations in this region, we investigated the physical fronts and their seasonal variations and clarified the spatiotemporal patterns of physical-biogeochemical factors as well as their interactions and synergies. The results show that pronounced physical fronts were present in the study area. Specifically, arc-and "S"-shaped thermal fronts existed off the shoal in summer and winter, respectively. The saline front largely expanded southeastward in spring, autumn, and winter, while it expanded northeastward in summer. The turbidity over the shoal was high year-round, and a marked turbidity front was formed between the nearshore water and the offshore seawater. The seasonal patterns and variations of the physical fronts significantly influenced material transport. During cold seasons, the frontal system was responsible for the significant turbid water plume expanding in a southeastern direction from the Jiangsu Coast. In summer, the arc-shaped thermal front confined the turbid water within the shoal. The expansion of excess dissolved inorganic nitrogen was consistent with the saline front, and the vertical transport of nutrients by upwelling occurred off the shoal in summer. Due to favorable conditions, the frontal region off the shoal is prone to high chlorophyll a (Chl-a) and may act as oases in either summer or winter. A conceptual diagram is assembled to provide an overview of physical-biogeochemical-ecological interactions off the Jiangsu Shoal in the western YS. Plain Language Summary The frequent occurrence of ecological disasters has posed a substantial threat to the western Yellow Sea (YS) ecosystem in recent years. Studying the environmental characteristics and biogeochemical processes in this area can contribute to an understanding of regional oceanography and lay a foundation for research on relevant ecological processes. Here, specific research on the physical fronts in the western YS and their seasonal variations was conducted, and the spatial-temporal patterns of physical-biogeochemical factors as well as their interactions and synergies in this region were explored. We show that pronounced thermohaline and turbidity fronts exist in the Jiangsu Shoal and its adjacent area. The distribution morphology and seasonal variations of thermohaline fronts potentially influence material transport. The frontal region off the Jiangsu Shoal is prone to high chlorophyll a in either summer or winter. The Jiangsu Shoal front could also play a role in shaping the distributions of ecological disasters (e.g., algae and jellyfish blooms). This work offers an overview of the coupled hydro-biogeochemical processes and ecological effects in the western YS and provides a scientific basis for the depiction of physical-biogeochemical dynamics.