Primary production at 47°N and 20°W in the North Atlantic Ocean: a comparison between the 14C incubation method and the mixed layer carbon budget

Abstract. A carbon budget has been established for the North Sea, a shelf sea on the NW European continental shelf. The carbon exchange fluxes with the North Atlantic Ocean dominate the gross carbon budget. The net carbon budget – more relevant to the issue of the contribution of the coastal ocean to the marine carbon cycle – is dominated by the carbon inputs from rivers, the Baltic Sea and the atmosphere. The North Sea acts as a sink for organic carbon and thus can be characterised as a heterotrophic system. The dominant carbon sink is the final export to the North Atlantic Ocean. More than 90% of the CO2 taken up from the atmosphere is exported to the North Atlantic Ocean making the North Sea a highly efficient continental shelf pump for carbon.

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Importance of dissolved organic nitrogen in the North Atlantic Ocean in sustaining primary production: a 3-D modelling approach

Biogeosciences Discussions ◽

10.5194/bgd-5-1727-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 1727-1764 ◽

Cited By ~ 1

Author(s):

G. Charria ◽

I. Dadou ◽

J. Llido ◽

M. Drévillon ◽

V. Garçon

Keyword(s):

Atlantic Ocean ◽

Primary Production ◽

North Atlantic ◽

Dissolved Organic Nitrogen ◽

Organic Nitrogen ◽

North Atlantic Ocean ◽

Subtropical Gyre ◽

Ekman Transport ◽

The North ◽

The North Atlantic

Abstract. An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical North Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN.m−2.yr−1 over the domain (13°–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN.s-1) confirms the estimation (17.9 kmolN.s-1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN.m−2.yr-1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the North Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

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Eddy-induced enhancement of primary production in a model of the North Atlantic Ocean

Nature ◽

10.1038/28373 ◽

1998 ◽

Vol 394 (6690) ◽

pp. 266-269 ◽

Cited By ~ 306

Author(s):

Andreas Oschlies ◽

Véronique Garçon

Keyword(s):

Atlantic Ocean ◽

Primary Production ◽

North Atlantic ◽

North Atlantic Ocean ◽

The North ◽

The North Atlantic

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The carbon budget of the North Sea

Biogeosciences Discussions ◽

10.5194/bgd-1-367-2004 ◽

2004 ◽

Vol 1 (1) ◽

pp. 367-392 ◽

Cited By ~ 2

Author(s):

H. Thomas ◽

Y. Bozec ◽

H. J. W. de Baar ◽

K. Elkalay ◽

M. Frankignoulle ◽

...

Keyword(s):

Atlantic Ocean ◽

Continental Shelf ◽

North Sea ◽

North Atlantic ◽

Carbon Budget ◽

North Atlantic Ocean ◽

Carbon Sink ◽

The North ◽

The North Sea ◽

The North Atlantic

Abstract. A carbon budget has been established for the North Sea, a shelf sea of the NW European continental shelf. The air-sea exchange of CO2 has been assessed as closing term of the budget. The carbon exchange fluxes with the North Atlantic Ocean dominate the gross carbon budget. The net carbon budget – more relevant to the issue of the contribution of the coastal ocean to the marine carbon cycle – is dominated by the carbon inputs from rivers, the Baltic Sea and the atmosphere. The dominant carbon sink is the final export to the North Atlantic Ocean. The North Sea acts as a sink for organic carbon. More than 90% of the CO2 taken up from the atmosphere is exported to the North Atlantic Ocean making the North Sea a highly efficient continental shelf pump for carbon.

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Estimating mixed layer nitrate in the North Atlantic Ocean

Biogeosciences ◽

10.5194/bg-7-795-2010 ◽

2010 ◽

Vol 7 (3) ◽

pp. 795-807 ◽

Cited By ~ 28

Author(s):

T. Steinhoff ◽

T. Friedrich ◽

S. E. Hartman ◽

A. Oschlies ◽

D. W. R. Wallace ◽

...

Keyword(s):

Neural Network ◽

Atlantic Ocean ◽

Observational Data ◽

Mixed Layer ◽

North Atlantic ◽

North Atlantic Ocean ◽

Mixed Layer Depth ◽

Model Data ◽

The North ◽

The North Atlantic

Abstract. Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic Ocean (40° N to 52° N, 10° W to 60° W). The equation was derived by multiple linear regression (MLR) from nitrate, sea surface temperature (SST) observational data and model mixed layer depth (MLD) data. The observational data were taken from merchant vessels that have crossed the North Atlantic on a regular basis in 2002/2003 and from 2005 to the present. It is important to find a robust and realistic estimate of MLD because the deepening of the mixed layer is crucial for nitrate supply to the surface. We compared model data from two models (FOAM and Mercator) with MLD derived from float data (using various criteria). The Mercator model gives a MLD estimate that is close to the MLD derived from floats. MLR was established using SST, MLD from Mercator, time and latitude as predictors. Additionally a neural network was trained with the same dataset and the results were validated against both model data as a "ground truth" and an independent observational dataset. This validation produced RMS errors of the same order for MLR and the neural network approach. We conclude that it is possible to estimate nitrate concentrations with an uncertainty of ±1.4 μmol L−1 in the North Atlantic.

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Importance of dissolved organic nitrogen in the north Atlantic Ocean in sustaining primary production: a 3-D modelling approach

Biogeosciences ◽

10.5194/bg-5-1437-2008 ◽

2008 ◽

Vol 5 (5) ◽

pp. 1437-1455 ◽

Cited By ~ 13

Author(s):

G. Charria ◽

I. Dadou ◽

J. Llido ◽

M. Drévillon ◽

V. Garçon

Keyword(s):

Atlantic Ocean ◽

Primary Production ◽

North Atlantic ◽

Dissolved Organic Nitrogen ◽

Organic Nitrogen ◽

North Atlantic Ocean ◽

Subtropical Gyre ◽

Ekman Transport ◽

The North ◽

The North Atlantic

Abstract. An eddy-permitting coupled ecosystem-circulation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical north Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molN m−2 yr−1 over the domain (13–35° N and 71–40° W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12° N, our estimate (18 kmolN s−1) confirms the estimation (17.9 kmolN s−1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molN m−2 yr−1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the north Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

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Influence of Rossby waves on primary production from a coupled physical-biogeochemical model in the North Atlantic Ocean

Ocean Science Discussions ◽

10.5194/osd-4-933-2007 ◽

2007 ◽

Vol 4 (6) ◽

pp. 933-967

Author(s):

G. Charria ◽

I. Dadou ◽

P. Cipollini ◽

M. Drévillon ◽

V. Garçon

Keyword(s):

Atlantic Ocean ◽

Primary Production ◽

North Atlantic ◽

Rossby Waves ◽

North Atlantic Ocean ◽

Inorganic Nitrogen ◽

Wave Crest ◽

Biogeochemical Model ◽

The North ◽

The North Atlantic

Abstract. How do Rossby waves influence primary production in the North Atlantic Ocean? Rossby waves have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms (reviewed in Killworth et al., 2004). In this study, we aim to investigate the role of the different physical processes to explain the surface chlorophyll signatures and the consequences on primary production using a 3-D coupled physical/biogeochemical model for the year 1998. The analysis at 20 given latitudes, mainly located in the subtropical gyre, where Rossby waves are strongly correlated with a surface chlorophyll signature, shows that vertical and horizontal processes are involved in the surface chlorophyll anomalies. Furthermore, the ecosystem response is, as expected, stronger when vertical input of dissolved inorganic nitrogen is observed. The surface chlorophyll anomalies, induced by these physical mechanisms, have an impact on primary production. We then estimate that Rossby waves induce, locally in space and time, increases (generally associated with the wave crest) and decreases (generally associated with the wave trough) in primary production (~±20% of the estimated primary production). This symmetrical situation suggests a net weak effect of Rossby waves on primary production.

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Estimating mixed layer nitrate in the North Atlantic Ocean

Biogeosciences Discussions ◽

10.5194/bgd-6-8851-2009 ◽

2009 ◽

Vol 6 (5) ◽

pp. 8851-8881

Author(s):

T. Steinhoff ◽

T. Friedrich ◽

S. E. Hartman ◽

A. Oschlies ◽

D. W. R. Wallace ◽

...

Keyword(s):

Neural Network ◽

Atlantic Ocean ◽

Observational Data ◽

Mixed Layer ◽

North Atlantic ◽

North Atlantic Ocean ◽

Mixed Layer Depth ◽

Model Data ◽

The North ◽

The North Atlantic

Abstract. Here we present an equation for the estimation of nitrate in surface waters of the North Atlantic Ocean (40° N to 52° N, 10° W to 60° W). The equation was derived by multiple linear regression (MLR) from nitrate, sea surface temperature (SST) observational data and model mixed layer depth (MLD) data. The observational data were taken from merchant vessels that have crossed the North Atlantic on a regular basis in 2002/2003 and from 2005 to present. It is important to find a robust and realistic esitmate of MLD because the deepening of the mixed layer is crucial for nitrate supply to the surface. We compared model data from two models (FOAM and Mercator) with MLD derived from float data (using various criteria). The Mercator model gives a MLD estimate that is close to the MLD derived from floats. MLR was established using SST, MLD from Mercator, time and latitude as predictors. Additionally a neural network was trained with the same dataset and the results were validated against both model data as a "ground truth" and an independent observational dataset. This validation produced RMS errors of the same order for MLR and the neural network approach. We conclude that it is possible to estimate nitrate concentrations with an uncertainty of ±1.5 μmol L−1 in the North Atlantic.

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