Upwelling off Yangtze River estuary in summer

Lü, Xingang; Qiao, Fangli; Xia, Changshui; Zhu, Jianrong; Yuan, Yue

doi:10.1029/2005jc003250

Cited by 102 publications

(117 citation statements)

References 27 publications

(40 reference statements)

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“…From the SST distribution, we found a strong cold water tongue appearing off Hangzhou Bay. Another low SST center was situated at 122-124 • E, 33 • N, near Jiangsu coast, which was consistent with the results reported by Lü et al (2006). The low-temperature region in surface layer water was usually an effective index for identifying the upwelling.…”

Section: Model Validationsupporting

confidence: 80%

Modeling the impact of river discharge and wind on the hypoxia off Yangtze Estuary

Zheng

Gao

Liu

et al. 2016

Nat. Hazards Earth Syst. Sci.

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Abstract. The phenomenon of low dissolved oxygen (known as hypoxia) in a coastal ocean system is closely related to a combination of anthropogenic and natural factors. Marine hypoxia occurs in the Yangtze Estuary, China, with high frequency and long persistence. It is related primarily to organic and nutrient enrichment influenced by river discharges and physical factors, such as water mixing. In this paper, a threedimensional hydrodynamic model was coupled to a biological model to simulate and analyze the ecological system of the East China Sea. By comparing with the observation data, the model results can reasonably capture the physical and biochemical dynamics of the Yangtze Estuary. In addition, the sensitive experiments were also used to examine the role of physical forcing (river discharge, wind speed, wind direction) in controlling hypoxia in waters adjacent to the Yangtze Estuary. The results showed that the wind field and river discharge have significant impact on the hypoxia off the Yangtze Estuary. The seasonal cycle of hypoxia was relatively insensitive to synoptic variability in the river discharge, but integrated hypoxic areas were sensitive to the whole magnitude of river discharge. Increasing the river discharge was shown to increase hypoxic areas, while decreasing the river discharge tended to decrease hypoxic areas. The variations of wind speed and direction had a great impact on the integrated hypoxic areas.

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Section: Model Validationsupporting

confidence: 80%

Modeling the impact of river discharge and wind on the hypoxia off Yangtze Estuary

Zheng

Gao

Liu

et al. 2016

Nat. Hazards Earth Syst. Sci.

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“…In fact, a large part of the global deep ocean has vertical mixing in the order of 0.1 cm 2 s −1 . The wave-circulation coupled model has shown satisfactory performances in a series of circulation modeling studies in the Yellow Sea and East China Sea (Qiao et al 2004bLü et al 2006;Xia et al 2006). Preliminary results even indicate that the wave-induced mixing can improve a common problem in climate models known as the "too cold tongue" in the tropical Pacific (Song et al 2007).…”

Section: Introductionmentioning

confidence: 93%

A three-dimensional surface wave–ocean circulation coupled model and its initial testing

et al. 2010

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A theoretical framework to include the influences of nonbreaking surface waves in ocean general circulation models is established based on Reynolds stresses and fluxes terms derived from surface wave-induced fluctuation. An expression for the wave-induced viscosity and diffusivity as a function of the wave number spectrum is derived for infinite and finite water depths; this derivation allows the coupling of ocean circulation models with a wave number spectrum numerical model. In the case of monochromatic surface wave, the wave-induced viscosity and diffusivity are functions of the Stokes drift. The influence of the waveinduced mixing scheme on global ocean circulation models was tested with the Princeton Ocean Model, indicating significant improvement in upper ocean thermal structure and mixed layer depth compared with mixing obtained by the Mellor-Yamada scheme without the wave influence. For example, the model-observation correlation coefficient of the upper 100-m temperature along 35°N increases from 0.68 without wave influence to 0.93 with wave influence. The wave-induced Reynolds stress can reach up to about 5% of the wind stress in high latitudes, and drive 2-3 Sv transport in the global ocean in the form of mesoscale eddies with diameter of 500-1,000 km. The surface waveinduced mixing is more pronounced in middle and high latitudes during the summer in the Northern Hemisphere and in middle latitudes in the Southern Hemisphere.

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“…Fronts normally form natural barriers to the water transport (Wolanski and Hammer 1988) and, thus, decrease the horizontal and in turn vertical transport of the upwelled water masses. It has been shown that frontal zones could also be regions where the deep water is upwelled into the surface layer (Savidge 1976;James 1978;Lü et al 2006). Nevertheless, the generation of the front under the post-storm stage off the northeastern Hainan coast is a temporary phenomenon, which is gradually developing, and thus does not support the prerequisite condition of a frontal induced upwelling.…”

Section: Thermocline Variation At Different Wind Stagesmentioning

confidence: 99%

The influence of meteorological variation on the upwelling system off eastern Hainan during summer 2007–2008

Su¹,

Wang

Pohlmann³

et al. 2011

Ocean Dynamics

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The influence of meteorological variation, i.e., typhoon and precipitation events, on the coastal upwelling off the eastern Hainan Island was studied based on observations taken during two upwelling seasons. The observations were made in August 2007 and July 2008, respectively. We found that, in principle, similar structure of sea surface temperature and bottom temperature prevailed in both observational periods, providing evidence that upwelling events occur frequently during the summer monsoon along the eastern Hainan shelf. Based on a simple momentum balance theory, we studied the balances between momentum fluxes, wind stress, and bottom stress. The results showed that the Burger number is S ≈ 1, indicating that the crossshelf momentum flux divergence was balanced by the wind stress and the onshore return flow occurred in the interior of the water column. Hence, a conceptual model of the upwelling structure was built for further understanding of upwelling events. In addition, it was also observed that variations in the strength of upwelling are controlled by storm events, i.e., strong northerly winds change the structure of the thermocline on the shelf significantly. The strong mixing caused by wind reduces the strength of the thermocline, in particular in coastal seas. Based on our conceptual model, a frontal zone between mixed coastal water and offshore water develops which destabilizing the water column and hence decreases the upwelling strength. Freshwaters from the two main rivers in the Wenchang Bay are confined to the coastal area less than 20-30 m deep, as confirmed by our water mass analysis. Freshwater discharge stabilized the water column, inhibiting the upwelling as shown by the potential energy calculation. Consequently, estuarine water only inhibits the upwelling in the near coastal area. Therefore, it can be concluded that estuarine water does not have a significant impact on upwelling strength on the shelf.

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Upwelling off Yangtze River estuary in summer

Cited by 102 publications

References 27 publications

Modeling the impact of river discharge and wind on the hypoxia off Yangtze Estuary

Modeling the impact of river discharge and wind on the hypoxia off Yangtze Estuary

A three-dimensional surface wave–ocean circulation coupled model and its initial testing

The influence of meteorological variation on the upwelling system off eastern Hainan during summer 2007–2008

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