The impact of wind mixing on the variation of bottom dissolved oxygen off the Changjiang Estuary during summer

Ni, Xiaobo; Huang, Daji; Zeng, Dingyong; Zhang, Tao; Li, Hongliang; Chen, Jianfang

doi:10.1016/j.jmarsys.2014.11.010

Cited by 94 publications

(78 citation statements)

References 19 publications

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“…(c) The deviation in summer (7-9 months) bottom dissolved oxygen concentration of wind direction variation runs from the base model. hypoxia Ni et al, 2014). Our simulated results showed that the variation in wind speed and direction significantly influences the stratification and hence the hypoxic area.…”

Section: Wind Forcingmentioning

confidence: 68%

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: Wind Forcingmentioning

confidence: 68%

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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“…This oxygen‐depletion rate is the fastest measured in this region by in situ observation. At the buoy, post‐storm bottom water DO declined with a daily mean depletion rate of 19.5 μ mol L −1 d −1 (15–20 August) (Ni et al ). These post‐Morakot DO drawdown rates fall near the upper range of planktonic community respiration rates previously reported for this shelf system (0.3–23.7 μ mol L −1 d −1 ; Chen et al ).…”

Section: Discussionmentioning

confidence: 99%

“…Low‐oxygen conditions develop in late spring and early summer, reaching a maximum in spatial extent during mid‐summer or sometimes early autumn before disappearing in late autumn (Wang et al ). Recent studies have related this seasonal hypoxia to particulate organic matter (POM) decomposition (Chen et al ), bottom bathymetry (Wang et al ), bottom water residence time (Rabouille et al ), upwelling of subsurface water (Chen et al ), water‐column stratification (Zhou et al ), and wind intensity (Ni et al ).…”

mentioning

confidence: 99%

Diatom bloom‐derived bottom water hypoxia off the Changjiang estuary, with and without typhoon influence

Wang

Chen

Jin

et al. 2017

Limnology & Oceanography

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117

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During the summers of 2009 and 2013, seawater pH and concentrations of dissolved oxygen, inorganic carbon, and nutrients were measured off the Changjiang estuary in the East China Sea. The 2009 cruise captured the effects of Typhoon Morakot; the 2013 cruise sampled more typical conditions (no typhoon). Data from both years indicate a close correlation between high primary productivity in surface waters and hypoxia in bottom waters. Based on these observations, we developed a conceptual model to guide an exploration of processes contributing to the formation of summertime bottom hypoxia. A mixing-model analysis of the 2009 data identified a surface diatom bloom as the major (70-80%) source of the organic carbon that decomposed and ultimately led to bottom water hypoxia. Within the Changjiang River plume, depth-integrated net biological production in the water column was 1.8 g C m 22 d 21 , indicating strong autotrophic production, which in turn led to a high respiration rate of 1.2 g C m 22 d 21 in the bottom water. During both cruises, strong surface-to-bottom physical and metabolic coupling was evident. In 2009, storm-driven inputs of nutrients from elevated river discharge and strong vertical mixing helped to fuel the rapid development of a surface diatom bloom. Afterwards, stratified conditions re-established, newly formed labile organic matter sank, and bottom water oxygen was quickly consumed to an extent that hypoxia and acidification developed. To our knowledge, the observed rate of hypoxia and acidification development (within 6 d) is the fastest yet reported for the Changjiang River plume.Oxygen-minimum zones in open-ocean waters and hypoxic zones in coastal waters have received increased attention in recent research related to changing biogeochemical and climate conditions. Oceanic oxygen-minimum zones occur naturally and permanently at depths of 200-1000 m in the open ocean (Wyrtki 1962). In contrast, coastal hypoxia (dissolved oxygen [DO] <63 lmol L 21 ) appears seasonally and is believed to be largely associated with anthropogenic eutrophication. Where nutrient inputs to coastal waters result in excess primary production, depletion of oxygen in bottom waters may follow (Diaz and Rosenberg 2008; Bianchi et al.

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“…The typhoon‐induced episodic transports of terrigenous materials often led to primary production alterations, which were found in the Gulf of Mexico (Conner et al, ), Pamlico Sound (Paerl et al, ), Sargasso Sea (Babin et al, ), South China Sea (Lin et al, ), Pearl River Estuary (Zhao et al, ), and Changjiang River Estuary (Wang et al, ). Moreover, dissolved oxygen concentrations in the bottom water are also modulated after the typhoon passage, for instance in the Charlotte Harbor (Tomasko et al, ) and the Changjiang River Estuary (Ni et al, ).…”

Section: Introductionmentioning

confidence: 99%

Dynamical Response of Changjiang River Plume to a Severe Typhoon With the Surface Wave‐Induced Mixing

Zhang

Yin

2018

JGR Oceans

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Typhoons (or hurricanes) are the most energetic atmospheric forcing acting on coastal waters. Here in this study, we investigated the response of the summertime Changjiang River plume to a typical typhoon, Chan‐hom (1509), with a combination of field observation and numerical simulation. Surface wave‐induced mixing was considered in the model configuration. The results showed that the typical offshore‐extending summer Changjiang River plume completely disappeared under the influence of typhoon wind. Instead, it extended southward along the Zhejiang and Fujian (Zhe‐Min) coast as a typical wintertime Changjiang River plume. The along‐shelf plume extension lasted for extra ~10 days after the typhoon passage, until another strong weather event came. The competition between wind‐driven current and buoyancy‐driven current dominated the recovery of the Changjiang River plume. Through calculation, we found that the freshwater transported to the Zhe‐Min Coastal Water reached ~4.7 × 1010 m3 as influenced by typhoon Chan‐hom, which was ~5% of the total Changjiang River discharge in 2015 or ~12% of the total dry season Changjiang River discharge (October‐April) when the majority of Changjiang River plume extended to Zhe‐Min Coastal Water. The remote sensing data of chlorophyll‐α from Geostationary Ocean Color Imager also showed that significant algal bloom occurred when the southward extending Changjiang River plume retreated. Surface wave‐induced mixing caused by typhoon wind was found to be important in destroying the vertical plume stratification and elongating the recovery processes from the typhoon influence.

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The impact of wind mixing on the variation of bottom dissolved oxygen off the Changjiang Estuary during summer

Cited by 94 publications

References 19 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

Diatom bloom‐derived bottom water hypoxia off the Changjiang estuary, with and without typhoon influence

Dynamical Response of Changjiang River Plume to a Severe Typhoon With the Surface Wave‐Induced Mixing

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