Nitrogen and carbon cycling in the North Sea and exchange with the North Atlantic—A model study. Part I. Nitrogen budget and fluxes

Pätsch, Johannes; Kühn, Wilfried

doi:10.1016/j.csr.2007.12.013

Cited by 88 publications

(94 citation statements)

References 40 publications

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“…In addition, the "microbial loop" (Azam et al, 1983) is represented. ECOHAM simulates the cycles of carbon (C), N, P, silicon (Si) and O 2 (Pätsch and Kühn, 2008;Lorkowski et al, 2012). The present version of ECOHAM is identical to that used by Große et al (2016).…”

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

“…Here, we will only summarize the relevant features of the O 2 cycle. Figure 1 illustrates the O 2 cycle implemented to ECOHAM (Müller, 2008;Pätsch and Kühn, 2008), including the links to the cycles of C, N and P. The arrows indicate the loss or gain of a substance, e.g., NH + 4 is released during benthic remineralization and utilized during pelagic nitrification. The airsea flux of O 2 is parametrized according to Wanninkhof (1992).…”

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

“…The sediment is described by a simple zero-dimensional module (Pätsch and Kühn, 2008). Benthic re-mineralization follows a first-order approach inhibiting year-to-year accumulation of matter (Große et al, 2016).…”

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

“…Linking state variables are: dissolved inorganic C (DIC), NH denitrification is linked to benthic O 2 consumption according to Seitzinger and Giblin (1996), reducing the O 2 concentration in the deepest pelagic layer (Fennel et al, 2006). Explicit benthic nitrification and benthic anammox are not implemented (Pätsch and Kühn, 2008).…”

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

“…We use a three-dimensional (3D) model consisting of the physical model HAMSOM (HAMburg Shelf Ocean Model; Backhaus, 1985;Pohlmann, 1991Pohlmann, , 1996 and the biogeochemical model ECOHAM (ECOsystem model, HAMburg; Pätsch and Kühn, 2008;Kühn et al, 2010;Lorkowski et al, 2012;Große et al, 2016). HAMSOM is a baroclinic, primitive equation model using the hydrostatic and Boussinesq approximations (Pohlmann, 1991).…”

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

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A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

et al. 2017

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Oxygen (O 2 ) deficiency, i.e., dissolved O 2 concentrations below 6 mg O 2 L −1 , is a common feature in the southern North Sea. Its evolution is governed mainly by the presence of seasonal stratification and production of organic matter, which is subsequently degraded under O 2 consumption. The latter is strongly influenced by riverine nutrient loads, i.e., nitrogen (N) and phosphorus (P). As riverine P loads have been reduced significantly over the past decades, this study aims for the quantification of the influence of riverine and non-riverine N inputs on the O 2 dynamics in the southern North Sea. For this purpose, we present an approach to expand a nutrient-tagging technique for physical-biogeochemical models -often referred to as 'trans-boundary nutrient transports' (TBNT) -by introducing a direct link to the O 2 dynamics. We apply the expanded TBNT to the physical-biogeochemical model system HAMSOM-ECOHAM and focus our analysis on N-related O 2 consumption in the southern North Sea during 2000-2014. The analysis reveals that near-bottom O 2 consumption in the southern North Sea is strongly influenced by the N supply from the North Atlantic across the northern shelf edge. However, riverine N sources -especially the Dutch, German and British rivers -as well as the atmosphere also play an important role. In the region with lowest simulated O 2 concentrations (around 56 • N, 6.5 • E), riverine N on average contributes 39% to overall near-bottom O 2 consumption during seasonal stratification. Here, the German and the large Dutch rivers constitute the highest riverine contributions (11% and 10%, respectively). At a site in the Oyster Grounds (around 54.5 • N, 4 • E), the average riverine contribution adds up to 41%, even exceeding that of the North Atlantic. Here, highest riverine contributions can be attributed to the Dutch and British rivers adding up to almost 28% on average. The atmospheric contribution results in 13%. Our results emphasize the importance of anthropogenic N inputs and seasonal stratification for the O 2 conditions in the southern North Sea. They further suggest that reductions in the riverine and atmospheric N inputs may have a relevant positive effect on the O 2 levels in this region.

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Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

Section: The Hamsom-ecoham Modelmentioning

confidence: 99%

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A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

et al. 2017

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Variability of North Sea pH and CO₂ in response to North Atlantic Oscillation forcing

et al. 2013

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[1] High biological activity causes a distinct seasonality of surface water pH in the North Sea, which is a strong sink for atmospheric CO 2 via an effective shelf pump. The intimate connection between the North Sea and the North Atlantic Ocean suggests that the variability of the CO 2 system of the North Atlantic Ocean may, in part, be responsible for the observed variability of pH and CO 2 in the North Sea. In this work, we demonstrate the role of the North Atlantic Oscillation (NAO), the dominant climate mode for the North Atlantic, in governing this variability. Based on three extensive observational records covering the relevant levels of the NAO index, we provide evidence that the North Sea pH and CO 2 system strongly responds to external and internal expressions of the NAO. Under positive NAO, the higher rates of inflow of water from the North Atlantic Ocean and the Baltic outflow lead to a strengthened north-south biogeochemical divide. The limited mixing between the north and south leads to a steeper gradient in pH and partial pressure of CO 2 (pCO 2 ) between the two regions in the productive period. This is exacerbated further when coinciding with higher sea surface temperature, which concentrates the net community production in the north through shallower stratification. These effects can be obscured by changing properties of the constituent North Sea water masses, which are also influenced by NAO. Our results highlight the importance of examining interannual trends in the North Sea CO 2 system with consideration of the NAO state.Citation: Salt, L. A

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Radium isotopes as a tracer of sediment‐water column exchange in the North Sea

Burt

Thomas

Pätsch

et al. 2014

Global Biogeochemical Cycles

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Sediment-water column exchange plays an important role in coastal biogeochemistry. We utilize short-lived radium isotopes ( 224 Ra and 223 Ra) to understand and quantify the dominant processes governing sediment-water column exchange throughout the North Sea. Our comprehensive survey, conducted in September 2011, represents the first of its kind conducted in the North Sea. We find that two main sources regulate surface Ra distributions: minor coastal input from rivers and shallow mudflats and North Sea sediments as the dominant source. Pore waters show 100-fold larger activities than the water column. North Sea sediment characteristics such as porosity and mean grain size, as well as turbulence at the sediment-water interface, are the dominant factors contributing to variability of Ra efflux. Ra inventory and mass balance approaches consistently yield high benthic Ra effluxes in the southern North Sea, driven by strong tidal and wind mixing, which in turn cause high sediment irrigation rates. These results exceed incubation-based Ra flux estimates and the majority of previously reported Ra flux estimates for other regions. Ra-based estimates of benthic alkalinity fluxes compare well to observed values, and the high rates of Ra efflux imply a potentially significant exchange of other products of sedimentary reactions, including carbon and nutrient species. Passive tracer simulations lend strong support to the Ra source attribution and imply seasonal variation in the surface water Ra distribution depending on stratification conditions.

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Nitrogen and carbon cycling in the North Sea and exchange with the North Atlantic—A model study. Part I. Nitrogen budget and fluxes

Cited by 88 publications

References 40 publications

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

Variability of North Sea pH and CO₂ in response to North Atlantic Oscillation forcing

Radium isotopes as a tracer of sediment‐water column exchange in the North Sea

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Nitrogen and carbon cycling in the North Sea and exchange with the North Atlantic—A model study. Part I. Nitrogen budget and fluxes

Cited by 88 publications

References 40 publications

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

Variability of North Sea pH and CO2 in response to North Atlantic Oscillation forcing

Radium isotopes as a tracer of sediment‐water column exchange in the North Sea

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Product

Resources

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Variability of North Sea pH and CO₂ in response to North Atlantic Oscillation forcing