German Bight estuaries: An inter-comparison on the basis of numerical modeling

Stanev, Emil V.; Jacob, Benjamin; Pein, Johannes

doi:10.1016/j.csr.2019.01.001

Cited by 43 publications

(39 citation statements)

References 55 publications

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“…An analysis of satellite data and in situ suspended matter data (Schartau et al, 2019) supports the model results by showing sharper gradients along the southern Wadden Sea than along the northern Wadden Sea. However, further model analyses including a quantification of transport rates based on multidecadal runs performed on higher resolution setups (see e.g., Gräwe et al, 2016;Androsov et al, 2019;Stanev et al, 2019) are needed to better understand the relative contribution of estuarine circulation and direct river inputs on the maintenance of horizontal gradients within the Wadden Sea.…”

Section: Limiting Factors Of Phytoplankton Growth In the Wadden Seamentioning

confidence: 99%

Wadden Sea Eutrophication: Long-Term Trends and Regional Differences

Beusekom¹,

Carstensen

Dolch

et al. 2019

Front. Mar. Sci.

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The Wadden Sea is a shallow intertidal coastal sea, largely protected by barrier islands and fringing the North Sea coasts of Netherlands, Germany, and Denmark. It is subject to influences from both the North Sea and major European rivers. Nutrient enrichment from these rivers since the 1950s has impacted the Wadden Sea ecology including loss of seagrass, increased phytoplankton blooms, and increased green macroalgae blooms. Rivers are the major source of nutrients causing Wadden Sea eutrophication. The nutrient input of the major rivers impacting the Wadden Sea reached a maximum during the 1980s and decreased at an average pace of about 2.5% per year for total Nitrogen (TN) and about 5% per year for total Phosphorus (TP), leading to decreasing nutrient levels but also increasing N/P ratios. During the past decade, the lowest nutrient inputs since 1977 were observed but these declining trends are leveling out for TP. Phytoplankton biomass (measured as chlorophyll a) in the Wadden Sea has decreased since the 1980s and presently reached a comparatively low level. In tidal inlet stations with a long-term monitoring, summer phytoplankton levels correlate with riverine TN and TP loads but stations located closer to the coast behave in a more complex manner. Regional differences are observed, with highest chlorophyll a levels in the southern Wadden Sea and lowest levels in the northern Wadden Sea. Model data support the hypothesis that the higher eutrophication levels in the southern Wadden Sea are linked to a more intense coastward accumulation of organic matter produced in the North Sea.

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Section: Limiting Factors Of Phytoplankton Growth In the Wadden Seamentioning

confidence: 99%

Wadden Sea Eutrophication: Long-Term Trends and Regional Differences

Beusekom¹,

Carstensen

Dolch

et al. 2019

Front. Mar. Sci.

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“…5c-e, Fig. 1; for position of ETM see Stanev et al, 2019;Kappenberg and Fanger, 2007). At Cuxhaven station observations indicate a bi-modal annual signal with peak concentrations of around 10 mmol m -3 ( Fig.…”

Section: Nutrientsmentioning

confidence: 97%

“…The hydrodynamical core of our Elbe-model consists of the SCHISM (Zhang and Baptista, 2008;Zhang et al, 2016) applied to the year 2010 topography (downloaded from www.portal-tideelbe.de). In the recent years, SCHISM has been successfully applied for the estuarine modelling (Pein et al, 2014;Ye et al, 2018;Liu et al, 2018;Stanev et al 2019). For simulation of the Elbe estuary we adopt the necessary techniques, such as vertical and horizontal scale resolving coordinates on an unstructured mesh and sigma coordinates, the drying and wetting algorithm, TVD advection scheme, 2 equation turbulence model, parallel implementation to run on supercomputers.…”

Section: Modelmentioning

confidence: 99%

“…In the vertical the model mesh has 21 s-coordinates. At the open ocean boundary sea level, horizontal currents, salinity and temperature are constrained by hourly outputs from an unstructured model of the German Bight (Stanev et al, 2019) that has been integrated for the period of 1 January 2012 until 31 December 2013. Daily discharge measurements by the German waterways agency (WSV, www.portal-tideelbe.de) stipulate the Elbe river freshwater contribution to the Elbe estuary.…”

Section: Physical Set-upmentioning

confidence: 99%

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Nitrogen cycling in the Elbe estuary from a joint 3D-modelling and observational perspective

Pein

Eisele

Hofmeister

et al. 2019

Preprint

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Abstract. The study addresses the nitrogen cycling in Elbe estuary. Observations of salinity, nutrients and oxygen from moored stations, ship casts and helicopter surveys are presented. Observations are complemented by simulations obtained from a coupled physical-biogeochemical 3D unstructured model, applied for the first time to the estuarine environment. Model simulations reproduce the temporal variability of nutrients and oxygen along the estuarine salinity gradient. Both, observations and model results, demonstrate mostly conservative mixing of nitrate and non-conservative behavior of ammonium. Model hind-casts of the years 2012 and 2013 provide a detailed reconstruction of nitrogen recycling with ammonium appearing as the key species of the remineralisation process. Estuarine turnover processes are fueled by inputs of diatoms and organic nitrogen at the tidal weir with intense primary production manifest in the shallow river section downstream of the weir. The harbor area is the hot spot of heterotrophic decay associated with growth of meso-zooplankton, sedimentation of degradable material, remineralisation, oxygen depletion, denitrification and ammonium production. In the harbor, biochemistry shows strong vertical gradients while hydrodynamics demonstrate connectivity between the main channel and the harbor. At the estuary bed nitrogen is deposited during spring and early summer. Resuspension leads to nearly closed budget by the end of the year. During the Elbe flood in June 2013, estuarine biogeochemistry is significantly disturbed with the harbor being deactivated as hot spot of heterotrophic decay. Plankton and organic matter are flushed towards the outer estuary which in consequence sees high abundance of grazers, oxygen depletion and elevated release of ammonium.

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“…Since the first 3D models of the North Sea (Backhaus, 1985;Dippner, 1993;Schrum, 1997), computational capacity has been significantly improved, which resulted in development of ever finer resolution setups that can resolve meso-scale features 320 such as the coastal freshwater fronts and baroclinic eddies (Holt and James, 2006;Pohlmann, 2006;Staneva et al, 2009;Pätsch et al, 2017) and the smaller-scale dynamics, such as the estuarine mixing Stanev et al, 2019). For large-domain biogeochemical applications that require a costly calculation of transport of dozens of additional state variables, the coarse-resolution models (10-20 km) are being actively used (e.g., Ford et al, 2017;Große et al, 2016;Daewel et al, 2019).…”

mentioning

confidence: 99%

Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system

Kerimoglu¹,

Voynova²,

Chegini³

et al. 2020

Preprint

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Abstract. The German Bight was exposed to record high riverine discharges in June 2013, as a result of flooding of the Elbe and Weser rivers. Several anomalous observations suggested that the hydrodynamical and the biogeochemical state of the system was impacted by this event. In this study, we developed a biogeochemical model and coupled it with a previously introduced high resolution hydrodynamical model of the southern North Sea, in order to better characterize these impacts, and gain insight into the underlying processes. Performance of the model was assessed using an extensive set of in-situ measurements for the period 2011&#8211;2014. We first improved the realism of the hydrodynamic model with regard to the representation of cross-shore gradients, mainly through inclusion of flow-dependent horizontal mixing. Among other characteristic features of the system, the coupled model system can reproduce the low salinities, high nutrient concentrations and low oxygen concentrations in the bottom layers observed within the German Bight following the flood event. Through a scenario analysis, we examined the sensitivity of the patterns observed during July 2013 to the hydrological and meteorological forcing in isolation. Within the region of freshwater influence (ROFI) of the Elbe-Weser rivers, the flood event clearly dominated the changes in salinity and nutrient concentrations, as expected. However, our findings point out to the relevance of the peculiarities in the meteorological conditions in 2013 as well: a combination of low wind speeds, warm air temperatures and cold bottom water temperatures resulted in a strong thermal stratification in the outer regions, and limited vertical nutrient transport to the surface layers. Within the central region, the thermal and haline dynamics interactively resulted in an intense density stratification. This intense stratification, in turn, led to enhanced primary production within the central region enriched by nutrients due to the flood, but reduction within the nutrient-limited outer region, and it caused a wide-spread oxygen depletion in bottom waters. Our results further point to the enhancement of the current velocities at the surface as a result of haline stratification, and intensification of the thermohaline estuarine-like circulation at the Wadden Sea, both driven by the flood event.

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German Bight estuaries: An inter-comparison on the basis of numerical modeling

Cited by 43 publications

References 55 publications

Wadden Sea Eutrophication: Long-Term Trends and Regional Differences

Wadden Sea Eutrophication: Long-Term Trends and Regional Differences

Nitrogen cycling in the Elbe estuary from a joint 3D-modelling and observational perspective

Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system

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