Diffusive boundary layer influenced by bottom boundary hydrodynamics in tidal flows

Wang, Jianing; Wei, Hao; Lu, Youyu; Zhao, Liang

doi:10.1002/2013jc008900

Cited by 6 publications

(2 citation statements)

References 23 publications

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“…3). HydroBioSed did not account for the thinning of the viscous layer at the seabed-water interface in response to wave-induced turbulence, which would act to further increase the oxygen gradient during erosional time periods (Gundersen and Jorgensen, 1990;Chatelain and Guizien, 2010;Wang et al, 2013). This implies that our current model estimates of oxygen diffusion into the seabed during resuspension events are conservative.…”

Section: Implications Of Model Development and Future Workmentioning

confidence: 98%

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

et al. 2017

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Abstract. Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed-watercolumn interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sediment-water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2-month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed-water interface. This enhanced supply of oxygen to the seabed, as well as resuspension-induced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water column. Additionally, entrainment of POM into the water column during resuspension events, and the associated increase in remineralization there, also increased oxygen consumption in the region of the water column below the pycnocline. During these resuspension events, modeled rates of oxygen consumption increased by factors of up to ∼ 2 and ∼ 8 in the seabed and below the pycnocline, respectively. When averaged over 2 months, the intermittent cycles of erosion and deposition led to a ∼ 16 % increase of oxygen consumption in the seabed, as well as a larger increase of ∼ 140 % below the pycnocline. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhône Delta. Local resuspension likely has the most pronounced effect on Published by Copernicus Publications on behalf of the European Geosciences Union. The roles of resuspension, diffusion and biogeochemical processes...

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Section: Implications Of Model Development and Future Workmentioning

confidence: 98%

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

et al. 2017

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“…where D is the oxygen diffusion coefficient (m 2 s −1 ), C BBL is the DO concentration in the bottom boundary layer (µmol L −1 ), T denotes the temperature in the bottom boundary layer and T m the mean temperature of the dataset during the continuous measurement. L # Br could be calculated based on the measured current velocity according to Wang et al (2013). The oxygen diffusion coefficient (D) was obtained based on the bottom water temperature and salinity (Ramsing and Gundersen, 1994).…”

Section: Sample Collection and Analysismentioning

confidence: 99%

Summertime Oxygen Depletion and Acidification in Bohai Sea, China

et al. 2020

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Increasing attention has recently been drawn to oxygen depletion and ocean acidification in coastal seas and their impacts on the marine ecosystem. Intensive organic matter degradation combined with weak water exchange is considered to be mainly responsible for bottom water oxygen depletion and acidification. Hypoxia and acidification in the bottom water of Bohai Sea have been frequently observed in summer seasons over the past decade. In this study, monthly surveys were conducted along an inshore-offshore transect in the north Bohai Sea from May to August in 2017 and 2018. The physical structure of the water column in the study area was characterized by a well-mixed surface layer and an essentially homogeneous deep layer that were separated by a strong pycnocline over the period from mid-Jun to late August in both years. Dissolved oxygen (DO), pH, and dissolved inorganic carbon (DIC) in the water column were also split into two layers by the pycnocline and varied little in each layer. No significant interannual variations were observed for the temporal progressions of DO, pH and DIC in the bottom water. Average DO concentration and pH in the bottom water linearly decreased with time from May to August while DIC presented an opposite trend. DO became increasingly unsaturated from mid-June to late August when DO decreased to 96 µmol L −1 and pH to 7.74. The molar ratio of net oxygen consumption to DIC production was 1.42, similar to the Redfield ratio (1.30). Pelagic respiration (>60%) linked to degradation of fresh organic matter prevailed over sediment respiration (<40%) in contributing to the oxygen depletion and acidification observed in this shallow water body. The duration and intensity of oxygen depletion and acidification in the study area were strongly affected by stormy weather events such as typhoons.

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Impact and recovery of pH in marine sediments subject to a temporary carbon dioxide leak

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Lichtschlag

Toberman

et al. 2015

International Journal of Greenhouse Gas Control

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Diffusive boundary layer influenced by bottom boundary hydrodynamics in tidal flows

Cited by 6 publications

References 23 publications

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

Summertime Oxygen Depletion and Acidification in Bohai Sea, China

Impact and recovery of pH in marine sediments subject to a temporary carbon dioxide leak

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