The mud deposits and the high turbidity in the Belgian–Dutch coastal zone, southern bight of the North Sea

Abstract. A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO2 exchanges in the Eastern Channel and Southern Bight of the North Sea, with focus on the eutrophied Belgian coastal waters. For this application, the model was implemented in a simplified three-box representation of the hydrodynamics with the open ocean boundary box ‘Western English Channel’ (WCH) and the ‘French Coastal Zone’ (FCZ) and ‘Belgian Coastal Zone’ (BCZ) boxes receiving carbon and nutrients from the rivers Seine and Scheldt, respectively. Results were obtained by running the model for the 1996–1999 period. The simulated partial pressures of CO2 (pCO2) were successfully compared with data recorded over the same period in the central BCZ at station 330 (51°26.05′ N; 002°48.50′ E). Budget calculations based on model simulations of carbon flow rates indicated for BCZ a low annual sink of atmospheric CO2 (−0.17 mol C m-2 y-1). On the opposite, surface water pCO2 in WCH was estimated to be at annual equilibrium with respect to atmospheric CO2. The relative contribution of biological, chemical and physical processes to the modelled seasonal variability of pCO2 in BCZ was further explored by running model scenarios with separate closures of biological activities and/or river inputs of carbon. The suppression of biological processes reversed direction of the CO2 flux in BCZ that became, on an annual scale, a significant source for atmospheric CO2 (+0.53 mol C m-2 y-1). Overall biological activity had a stronger influence on the modelled seasonal cycle of pCO2 than temperature. Especially Phaeocystis colonies which growth in spring were associated with an important sink of atmospheric CO2 that counteracted the temperature-driven increase of pCO2 at this period of the year. However, river inputs of organic and inorganic carbon were shown to increase the surface water pCO2 and hence the emission of CO2 to the atmosphere. Same calculations conducted in WCH, showed that temperature was the main factor controlling the seasonal pCO2 cycle in these open ocean waters. The effect of interannual variations of fresh water discharge (and related nutrient and carbon inputs), temperature and wind speed was further explored by running scenarios with forcing typical of two contrasted years (1996 and 1999). Based on these simulations, the model predicts significant variations in the intensity and direction of the annual air-sea CO2 flux.

Download Full-text

Carbon dynamics and CO2 air-sea exchanges in the eutrophied coastal waters of the southern bight of the North Sea: a modelling study

Biogeosciences Discussions ◽

10.5194/bgd-1-561-2004 ◽

2004 ◽

Vol 1 (1) ◽

pp. 561-589 ◽

Cited By ~ 9

Author(s):

N. Gypens ◽

C. Lancelot ◽

A. V. Borges

Keyword(s):

Coastal Zone ◽

North Sea ◽

Coastal Waters ◽

Water Discharge ◽

Co2 Flux ◽

Atmospheric Co2 ◽

Biogeochemical Model ◽

Southern Bight ◽

The North ◽

The North Sea

Abstract. A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO2 exchanges in the Eastern Channel and Southern Bight of the North Sea with focus on the eutrophied Belgian coastal waters. For this application the model was implemented in a simplified three-box representation of the hydrodynamics including the open ocean boundary box ‘Western English Channel’ (WCH) and the ‘French Coastal Zone’ (FCZ) and ‘Belgian Coastal Zone’ (BCZ) boxes receiving carbon and nutrients from the rivers Seine and Scheldt, respectively. Results were obtained by running the model for the 1996–1999 period. The predicted partial pressures of CO2 (pCO2) were successfully compared with data recorded over the same period in the central BCZ at station 330 (51°26.05′ N; 002°48.50′ E). Budget calculations based on model simulations of carbon flow rates indicated for BCZ a low annual sink of atmospheric CO2 (−0.17 mol C m−2 y−1). On the opposite surface water pCO2 in WCH was estimated in annual equilibrium with respect to atmospheric CO2. The relative contribution of biological, chemical and physical processes to the modelled pCO2 seasonal variability in BCZ was further explored by running model scenarios with separate closures of biological activities and carbon rivers inputs. The suppression of biological processes reversed direction of the CO2 flux in BCZ that became, on an annual scale, a significant source for atmospheric CO2 (+0.58 mol C m−2 y−1). Overall biological activity had a stronger influence on the modelled seasonal cycle of pCO2 than temperature. Especially Phaeocystis colonies which spring growth was associated with an important sink of atmospheric CO2 that counteracted the temperature-driven increase of pCO2 in spring. On the other hand, river inputs of organic and inorganic carbon were shown to increasing water pCO2 and hence emission of CO2 to the atmosphere. Same calculations conducted in WCH, showed that temperature was the main factor controlling the seasonal pCO2 cycle in these waters. The effect of interannual variations of fresh water discharge (and related nutrient and carbon inputs), temperature and wind speed was further explored by running scenarios with forcings typical of two contrasted years (1996 and 1999). Based on these simulations, the model predicts significant variations in the intensity and direction of the annual air-sea CO2 flux.

Download Full-text

An estimation of the effects of Ensis directus on the transport and burial of silt in the near-shore Dutch coastal zone of the North Sea

Journal of Sea Research ◽

10.1016/j.seares.2016.12.001 ◽

2017 ◽

Vol 127 ◽

pp. 95-104 ◽

Cited By ~ 1

Author(s):

Rob Witbaard ◽

Magda J.N. Bergman ◽

Evaline van Weerlee ◽

Gerard C.A. Duineveld

Keyword(s):

Coastal Zone ◽

North Sea ◽

The North ◽

Near Shore ◽

The North Sea

Download Full-text

The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea

Biogeosciences ◽

10.5194/bg-13-841-2016 ◽

2016 ◽

Vol 13 (3) ◽

pp. 841-863 ◽

Cited By ~ 19

Author(s):

H. Brenner ◽

U. Braeckman ◽

M. Le Guitton ◽

F. J. R. Meysman

Keyword(s):

Coastal Zone ◽

North Sea ◽

Dissolved Inorganic Carbon ◽

Co2 Uptake ◽

Overlying Water ◽

Southern North Sea ◽

The North ◽

Alkalinity Generation ◽

The North Sea ◽

The Impact

Abstract. It has been previously proposed that alkalinity release from sediments can play an important role in the carbonate dynamics on continental shelves, lowering the pCO2 of seawater and hence increasing the CO2 uptake from the atmosphere. To test this hypothesis, sedimentary alkalinity generation was quantified within cohesive and permeable sediments across the North Sea during two cruises in September 2011 (basin-wide) and June 2012 (Dutch coastal zone). Benthic fluxes of oxygen (O2), alkalinity (AT) and dissolved inorganic carbon (DIC) were determined using shipboard closed sediment incubations. Our results show that sediments can form an important source of alkalinity for the overlying water, particularly in the shallow southern North Sea, where high AT and DIC fluxes were recorded in near-shore sediments of the Belgian, Dutch and German coastal zone. In contrast, fluxes of AT and DIC are substantially lower in the deeper, seasonally stratified, northern part of the North Sea. Based on the data collected, we performed a model analysis to constrain the main pathways of alkalinity generation in the sediment, and to quantify how sedimentary alkalinity drives atmospheric CO2 uptake in the southern North Sea. Overall, our results show that sedimentary alkalinity generation should be regarded as a key component in the CO2 dynamics of shallow coastal systems.

Download Full-text