Modeling the carbon fluxes of the northwest European continental shelf: Validation and budgets

[1] Carbon budgets are simulated for the northwest European continental shelf and adjacent regions of the northeast Atlantic. Both physical and biological processes are evaluated, including exchanges between the water column and the atmosphere and sea bed. We use a multi-year simulation of a coupled 3D hydrodynamics-ecosystem model (POLCOMS-ERSEM) driven by realistic atmospheric data, ocean boundary conditions and freshwater inputs for 1989 to 2004. The northeast Atlantic (20°W to 13°E, 40°N to 65°N), including the European shelf, is found to be a net sink for atmospheric CO2. Biological processes exert a stronger control over pCO2than temperature, and hence have a stronger effect on the air-sea CO2 exchange. For the European shelf, carbon sources of rivers and the uptake of atmospheric CO2 are balanced by horizontal transport off shelf and there is little carbon burial. There is net transport of carbon onto the shelf in the top 180 m of the water column and off the shelf below that depth, with a net carbon loss of ∼6 ± 1 × 1012 mol C yr−1. Up to 50% of the carbon exported from the shelf is transported below the permanent pycnocline and so is isolated from release into the atmosphere on centennial timescales.

[1]  Jason T. Holt,et al.  Oceanic controls on the primary production of the northwest European continental shelf: model experiments under recent past conditions and a potential future scenario , 2012 .

[2]  Anthony J. Richardson,et al.  Error quantification of a high resolution coupled hydrodynamic- ecosystem coastal-ocean model: Part3, validation with Continuous Plankton Recorder data , 2006 .

[3]  L. G. Sillén,et al.  High-speed computers as a supplement to graphical methods--V. HALTAFALL, a general program for calculating the composition of equilibrium mixtures. , 1967, Talanta.

[4]  F. Wulff,et al.  Autotrophy, nitrogen accumulation and nitrogen limitation in the Baltic Sea: A paradox or a buffer for eutrophication? , 2003 .

[5]  Corinne Le Quéré,et al.  Trends in the sources and sinks of carbon dioxide , 2009 .

[6]  A. Borges,et al.  Carbon dynamics and CO2 air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study , 2004 .

[7]  A. Borges,et al.  High temporal coverage of carbon dioxide measurements in the Southern Bight of the North Sea , 2007 .

[8]  A. Watson,et al.  In situ evaluation of air‐sea gas exchange parameterizations using novel conservative and volatile tracers , 2000 .

[9]  Nicolas Gruber,et al.  The Oceanic Sink for Anthropogenic CO2 , 2004, Science.

[10]  E. F. Bradley,et al.  Bulk Parameterization of Air–Sea Fluxes: Updates and Verification for the COARE Algorithm , 2003 .

[11]  Jason Holt,et al.  Prediction and analysis of long‐term variability of temperature and salinity in the Irish Sea , 2007 .

[12]  T. Pohlmann,et al.  Investigation on the trophic state of the North Sea for three years (1994–1996) simulated with the ecosystem model ERSEM – the role of a sharp NAOI decline , 2004 .

[13]  J. Holt,et al.  An s coordinate density evolving model of the northwest European continental shelf: 1. Model description and density structure , 2001 .

[14]  Andrew J. Watson,et al.  Climatological Mean and Decadal Change in Surface Ocean Pco(2), and Net Sea-Air Co2 Flux Over the Global Oceans (Vol 56, Pg 554, 2009) , 2009 .

[15]  E. Fry,et al.  Absorption spectrum (380-700 nm) of pure water. II. Integrating cavity measurements. , 1997, Applied optics.

[16]  C. Culberson,et al.  MEASUREMENT OF THE APPARENT DISSOCIATION CONSTANTS OF CARBONIC ACID IN SEAWATER AT ATMOSPHERIC PRESSURE1 , 1973 .

[17]  K. Fennel,et al.  Quantifying biological carbon export for the northwest North Atlantic continental shelves , 2009 .

[18]  Yann Bozec,et al.  Response to Comment on "Enhanced Open Ocean Storage of CO2 from Shelf Sea Pumping" , 2004, Science.

[19]  Jerry Blackford,et al.  Ecosystem dynamics at six contrasting sites: a generic modelling study , 2004 .

[20]  Alberto Borges,et al.  Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2 , 2009 .

[21]  B. Delille,et al.  Carbon dioxide emission from european estuaries , 1998, Science.

[22]  C. Sweeney,et al.  Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects , 2002 .

[23]  B. Delille,et al.  Carbon dioxide in European coastal waters , 2006 .

[24]  J. Cole,et al.  Increase in the Export of Alkalinity from North America's Largest River , 2003, Science.

[25]  Jason T. Holt,et al.  The influence of initial conditions and open boundary conditions on shelf circulation in a 3D ocean-shelf model of the North East Atlantic , 2009 .

[26]  Jason T. Holt,et al.  The carbonate system in the North Sea: sensitivity and model validation , 2012 .

[27]  S. Gorshkov,et al.  World ocean atlas , 1976 .

[28]  S. Watanabe,et al.  Is there a “continental shelf pump” for the absorption of atmospheric CO2? , 1999 .

[29]  John M. Huthnance,et al.  Circulation, exchange and water masses at the ocean margin: the role of physical processes at the shelf edge , 1995 .

[30]  M. Fasham,et al.  An Examination of the “Continental shelf pump” in an open ocean general circulation model , 2001 .

[31]  Y. Bozec,et al.  The continental shelf pump for CO2 in the North Sea - evidence from summer observation , 2005 .

[32]  A. Olsen,et al.  Response of the Surface Ocean CO2 System in the Nordic Seas and Northern North Atlantic to Climate Change , 2013 .

[33]  Hyun‐cheol Kim,et al.  Significant contribution of dissolved organic matter to seawater alkalinity , 2009 .

[34]  Alejandro J. Souza,et al.  Flow structure and seasonalityin the Hebridean slope current , 2001 .

[35]  Jason T. Holt,et al.  A simulation of the southern North Sea in comparison with measurements from the North Sea Project Part 2 Suspended Particulate Matter , 1999 .

[36]  J. Holt,et al.  A simulation of the Southern North Sea in comparison with Measurements from the North Sea Project , 1999 .

[37]  B. Delille,et al.  Dissolved inorganic carbon dynamics and air‐sea carbon dioxide fluxes during coccolithophore blooms in the northwest European continental margin (northern Bay of Biscay) , 2010 .

[38]  A. Watson,et al.  Trends in North Atlantic sea-surface fCO2 from 1990 to 2006 , 2009 .

[39]  K. Fennel.  The role of continental shelves in nitrogen and carbon cycling: Northwestern North Atlantic case study , 2010 .

[40]  Jason T. Holt,et al.  Error quantification of a high-resolution coupled hydrodynamic-ecosystem coastal-ocean model: Part 2. Chlorophyll-a, nutrients and SPM , 2007 .

[41]  A. Borges,et al.  The Carbon budget of the North Sea , 2004 .

[42]  F. Millero,et al.  A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media , 1987 .

[43]  D. Haidvogel,et al.  A semi-implicit ocean circulation model using a generalized topography-following coordinate system , 1994 .

[44]  J. Holt,et al.  Error quantification of a high-resolution coupled hydrodynamic-ecosystem coastal-ocean model: Part 1 model overview and assessment of the hydrodynamics , 2005 .

[45]  J. Aiken,et al.  Semianalytical model for the derivation of ocean color inherent optical properties: description, implementation, and performance assessment. , 2006, Applied optics.

[46]  A. Borges,et al.  Controls of the surface water partial pressure of CO2 in the North Sea , 2005 .

[47]  K. Fennel,et al.  Denitrification effects on air‐sea CO2 flux in the coastal ocean: Simulations for the northwest North Atlantic , 2008 .

[48]  A. Borges,et al.  Distribution of surface carbon dioxide and air-sea exchange in the English Channel and adjacent areas , 2003 .

[49]  A. Borges,et al.  Enhanced ocean carbon storage from anaerobic alkalinity generation in coastal sediments , 2008 .

[50]  K. Haines,et al.  Evaluation of the S(T) assimilation method with the Argo dataset , 2009 .

[51]  A. Borges,et al.  Time series of the partial pressure of carbon dioxide (2001–2004) and preliminary inorganic carbon budget in the Scheldt plume (Belgian coastal waters) , 2006 .

[52]  A. Borges,et al.  European continental shelf as a significant sink for atmospheric carbon dioxide , 2001 .

[53]  A. Borges,et al.  Distribution of surface carbon dioxide and air‐sea exchange in the upwelling system off the Galician coast , 2002 .

[54]  J. C. Blackford,et al.  pH variability and CO2 induced acidification in the North Sea , 2007 .

[55]  J. Deming,et al.  The role of bacteria in the turnover of organic carbon in deep-sea sediments , 1985 .

[56]  A. Borges,et al.  Nitrogen and carbon cycling in the North Sea and exchange with the North Atlantic—A model study, Part II: Carbon budget and fluxes , 2008 .

[57]  A. Borges,et al.  Effect of eutrophication on air–sea CO2 fluxes in the coastal Southern North Sea: a model study of the past 50 years , 2009 .

[58]  Timothy T. Takahashi,et al.  An Assessment of the Role of the North Atlantic as a CO $_{2}$ Sink [and Discussion] , 1995 .

[59]  Andrew J. Watson,et al.  A variable and decreasing sink for atmospheric CO2 in the North Atlantic , 2007 .

[60]  Jason T. Holt,et al.  Down‐welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump , 2009 .

[61]  J. Marotzke,et al.  Factors influencing anthropogenic carbon dioxide uptake in the North Atlantic in models of the ocean carbon cycle , 2008 .

[62]  A. Borges,et al.  Mechanisms controlling the air–sea CO2 flux in the North Sea , 2009 .

[63]  A. Borges.  Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean? , 2005 .