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Shi J.,Key Laboratory of Physical Oceanography | Shi J.,Ocean University of China | Cheng Y.,Ocean University of China | Jiao Y.,Ocean University of China | Hou J.,Ocean University of China
Chinese Journal of Oceanology and Limnology | Year: 2011

Supercooled water with temperatures below freezing point, was identified from hydrographic data obtained by Chinese and Australian expeditions to Prydz Bay, Antarctica, during the austral summer. The study shows that most supercooled waters occurred at depths of 63-271 m in the region north of the Amery Ice Shelf (AIS) front. The maximum supercooling was 0. 16°C below the in-situ freezing point. In temperature and salinity ranges of -2. 14-1. 96°C and 34. 39-34. 46, respectively, the water was colder and fresher than peripheral shelf water. The supercooled water had less variability in the vertical profiles compared to shelf water. Based on analysis of their thermohaline features and spatial distribution, as well as the circulation pattern in Prydz Bay, we conclude that these supercooled waters originated from a cavity beneath the AIS and resulted from upwelling just outside of the AIS front. Water emerging from the ice shelf cools to an extremely low temperature (about -2. 0°C) by additional cooling from the ice shelf, and becomes buoyant with the addition of melt water from the ice shelf base. When this water flows out of the ice shelf front, its upper boundary is removed, and thus it rises abruptly. Once the temperature of this water reaches below the freezing point, supercooling takes place. In summer, the seasonal pycnocline at ~100 m water depth acts as a barrier to upwelling and supercooling. The upwelling of ice shelf outflow water illuminates a unique mid-depth convection of the polar ocean. © 2011 Chinese Society for Oceanology and Limnology, Science Press and Springer Berlin Heidelberg. Source

Yuan Y.,Ocean University of China | Song D.,Key Laboratory of Physical Oceanography | Wu W.,Ocean University of China | Liang S.,Ocean University of China | And 2 more authors.
Regional Studies in Marine Science | Year: 2016

In this study, marine environmental issues that occurred during the socio-economic development of Qingdao City and the exploitation and utilization of Jiaozhou Bay (JB) are reviewed. Its environmental condition has been dominated by intensive anthropogenic activities, i.e. increased wastewater discharge and rapid coastline evolution, which have reduced the ecosystem's ability to sustain itself. Efforts have been taken in scientific research and coastal management to protect and restore the environment in JB since 1990s. But lack of holistic views of JB system generates knowledge gaps in different research disciplines as well as the linkage between science and management. A case study is given to illustrate that different pollutant indicators respond to the coastline evolution differently, which cannot be explained by physics sole. The integrated research by knowledge sharing through community-benefit research projects is therefore called for on the systematic biogeochemical dynamics in JB. The integrated coastal zone management is also needed to cope with the complicated and complex systems of JB by an interdisciplinary problem-solving mechanism. © 2016 Elsevier B.V. Source

Song D.,Key Laboratory of Physical Oceanography | Song D.,University of New South Wales | Wang X.H.,University of New South Wales | Wang X.H.,State Key Laboratory of Satellite Ocean Environment Dynamics
Journal of Geophysical Research: Oceans | Year: 2013

A three-dimensional wave-current-sediment coupled numerical model with wetting and drying process is developed to understand hydrodynamics and sediment transport dynamics in the Deepwater Navigation Channel (DNC), the North Passage of the Yangtze River Estuary (YRE), China. The model results are in good agreement with observed data, and statistics show good model skill scores and correlation coefficients. The model well reproduces the spring-neap variation between a well-mixed estuary and a highly stratified estuary. Model results indicate that the estuarine gravitational circulation plays the most important role in the estuarine turbidity maximum (ETM) formation in the DNC. The upstream nonlocal sediment intrusion through the spillover mechanism is a major source of sediment trapping in the North Passage after the morphological changes. Numerical studies are conducted to show scenarios in the YRE under the effects of different forcings (river discharges, waves, and winds). Between these study cases, surface-wave-breaking relieves the sediment trapping and bottom-wave-current-interaction aggravates the bed erosion and elevates the SSC in the ETM; the former and the latter have the least and largest influence on the suspended sediment transport in the DNC. The wind effects have a greater influence on sediment trapping than the river discharges, and the steady northwesterly wind condition favors the siltation in the DNC most. The significance of density-driven turbidity current is also assessed, which can enhance the saline-water intrusion and suppress the turbulent mixing in the bottom boundary layer. © 2013. American Geophysical Union. All Rights Reserved. Source

Song D.,Key Laboratory of Physical Oceanography | Song D.,University of New South Wales | Wang X.H.,Key Laboratory of Physical Oceanography | Wang X.H.,University of New South Wales | And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2013

The in situ data in the Deepwater Navigation Channel (DNC), Yangtze River Estuary (YRE), China, in the dry season 2009, shows spring tides associated with greater maximum velocities, more mixing, less stratification, and diffused fluid mud; whereas neap tides are associated with smaller maximum velocities, greater stratification, inhibited mixing, and stratified fluid muds. The balance of salt flux indicates the seaward salt transport is dominated by fluvial flows, and the landward salt transport is generated by compensation flows during spring tides, but shear effects during neap tidal cycles. The balance of suspended sediment flux illustrates the offshore sediment transport is dominated by fluvial flows as well, but the onshore transport is induced by tidal-pumping effects on spring tides, and shear effects on neaps. The suspended sediment transport is strongly affected by the salinity distribution and salinity-gradient-induced stratification in the DNC. The spring-neap asymmetry is generated by the estuarine gravitational circulation during low-flow conditions; while the flood-ebb asymmetric stratification within a tidal cycle is due to the semidiurnal tidally movement of the salt front. © 2013. American Geophysical Union. All Rights Reserved. Source

Yang W.,Key Laboratory of Physical Oceanography | Yang W.,Ocean University of China | Zhao L.,Key Laboratory of Physical Oceanography | Zhao L.,Tianjin University of Science and Technology | And 10 more authors.
Journal of Ocean University of China | Year: 2013

During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea (ECS) were measured synchronously by a bottom-mounted fast sampling ADCP (acoustic Doppler current profiler) and a RBR CTD (RBR-620) profiler. While focusing on the tide-induced and stratification's impact on mixing, the Reynolds stress and the turbulent kinetic energy (TKE) production rate were calculated using the 'variance method'. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoyancy frequency of N2 ~ (1-6) × 10-3 s-2. The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear. © 2013 Science Press, Ocean University of China and Springer-Verlag Berlin Heidelberg. Source

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