The carbonate system in the North Sea: sensitivity and model validation

The ocean plays an important role in regulating the climate, acting as a sink for carbon dioxide, perturbing the carbonate system and resulting in a slow decrease of seawater pH. Understanding the dynamics of the carbonate system in shelf sea regions is necessary to evaluate the impact of Ocean Acidification (OA) in these societally important ecosystems. Complex hydrodynamic and ecosystem coupled models provide a method of capturing the significant heterogeneity of these areas. However rigorous validation is essential to properly assess the reliability of such models. The coupled model POLCOMS–ERSEM has been implemented in the North Western European shelf with a new parameterization for alkalinity explicitly accounting for riverine inputs and the influence of biological processes. The model has been validated in a like with like comparison with North Sea data from the CANOBA dataset. The model shows good to reasonable agreement for the principal variables, physical (temperature and salinity), biogeochemical (nutrients) and carbonate system (dissolved inorganic carbon and total alkalinity), but simulation of the derived variables, pH and pCO2, are not yet fully satisfactory. This high uncertainty is attributed mostly to riverine forcing and primary production. This study suggests that the model is a useful tool to provide information on Ocean Acidification scenarios, but uncertainty on pH and pCO2 needs to be reduced, particularly when impacts of OA on ecosystem functions are included in the model systems.

[1]  B. Eyre,et al.  Diel coral reef acidification driven by porewater advection in permeable carbonate sands, Heron Island, Great Barrier Reef , 2011 .

[2]  A. Dickson An exact definition of total alkalinity and a procedure for the estimation of alkalinity and total inorganic carbon from titration data , 1981 .

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

[4]  Andrew J. Watson,et al.  Ocean acidification due to increasing atmospheric carbon dioxide , 2005 .

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

[6]  Richard A. Feely,et al.  Impacts of ocean acidification on marine fauna and ecosystem processes , 2008 .

[7]  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 .

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

[9]  A. Dickson Thermodynamics of the dissociation of boric acid in synthetic seawater from 273.15 to 318.15 K , 1990 .

[10]  N. Oh,et al.  Anthropogenically enhanced fluxes of water and carbon from the Mississippi River , 2008, Nature.

[11]  K. Caldeira,et al.  Oceanography: Anthropogenic carbon and ocean pH , 2003, Nature.

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

[13]  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 .

[14]  L. Uppström The boron/chlorinity ratio of deep-sea water from the Pacific Ocean , 1974 .

[15]  N. Bates Interannual variability of the oceanic CO2 sink in the subtropical gyre of the North Atlantic Ocean over the last 2 decades , 2007 .

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

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

[18]  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 .

[19]  J. Blackford Predicting the impacts of ocean acidification: Challenges from an ecosystem perspective , 2010 .

[20]  F. Joos,et al.  Imminent ocean acidification in the Arctic projected with the NCAR global coupled carbon cycle-climate model , 2009 .

[21]  Andrew G. Dickson,et al.  Guide to best practices for ocean CO2 measurements , 2007 .

[22]  P. Ruardij,et al.  The European regional seas ecosystem model, a complex marine ecosystem model , 1995 .

[23]  A. Borges,et al.  Daily and seasonal variations of the partial pressure of CO2 in surface seawater along Belgian and southern Dutch coastal areas , 1999 .

[24]  R. Feely,et al.  The internal consistency of CO2 measurements in the equatorial Pacific , 1993 .

[25]  Stephan C. Meylan,et al.  CO2calc: A User-Friendly Seawater Carbon Calculator for Windows, Mac OS X, and iOS (iPhone) , 2010 .

[26]  Mike Grant,et al.  Evaluating the ability of a hydrodynamic ecosystem model to capture inter- and intra-annual spatial characteristics of chlorophyll-a in the north east Atlantic , 2011 .

[27]  B. Schneider,et al.  The seasonal cycle of carbon dioxide in Baltic Sea surface waters , 1999 .

[28]  H. Pörtner Ecosystem effects of ocean acidification in times of ocean warming: a physiologist’s view , 2008 .

[29]  A. Borges,et al.  Benthic remineralization in the northeast European continental margin (northern Bay of Biscay) , 2011 .

[30]  Scott C. Doney,et al.  Ocean Acidification: Present Conditions and Future Changes in a High-CO2 World , 2009 .

[31]  P. B. Duffy,et al.  Anthropogenic carbon and ocean pH , 2001 .

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

[33]  P. Andersson,et al.  Long term trends in the seas surrounding Sweden : Part one - Nutrients , 2006 .

[34]  A. Borges,et al.  Seasonal and inter-annual variability of air–sea CO2 fluxes and seawater carbonate chemistry in the Southern North Sea , 2011 .

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

[36]  A. Omstedt,et al.  Distribution, long-term development and mass balance calculation of total alkalinity in the Baltic Sea , 2008 .

[37]  Gerald G Singh,et al.  Meta-analysis reveals negative yet variable effects of ocean acidification on marine organisms. , 2010, Ecology letters.

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

[39]  Roger Proctor,et al.  Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea , 2010 .

[40]  Frank J. Millero,et al.  Distribution of alkalinity in the surface waters of the major oceans , 1998 .

[41]  T. Kana,et al.  Dynamic model of phytoplankton growth and acclimation: responses of the balanced growth rate and the chlorophyll a:carbon ratio to light, nutrient-limitation and temperature , 1997 .

[42]  R. Lukas,et al.  Physical and biogeochemical modulation of ocean acidification in the central North Pacific , 2009, Proceedings of the National Academy of Sciences.

[43]  E. Maier‐Reimer,et al.  Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms , 2005, Nature.

[44]  D. Wolf-Gladrow,et al.  On CO 2 pertubation experiments: over-determination of carbonate chemistry reveals inconsistencies , 2010 .

[45]  T. Blackburn,et al.  Anaerobic mineralization in marine sediments from the Baltic Sea-North Sea transition , 1990 .

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

[47]  Octavio Llinás,et al.  The interannual variability of oceanic CO2 parameters in the northeast Atlantic subtropical gyre at the ESTOC site , 2007 .

[48]  Momme Butenschön,et al.  Modeling the carbon fluxes of the northwest European continental shelf: Validation and budgets , 2012 .

[49]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[50]  R. Feely,et al.  Ocean acidification: the other CO2 problem. , 2009, Annual review of marine science.

[51]  Alberto V. Borgesa,et al.  Carbonate chemistry in the coastal zone responds more strongly to eutrophication than ocean acidification , 2010 .

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

[53]  B. Delille CO2 in Seawater: Equilibrium, Kinetics, Isotopes , 2002 .

[54]  R. Weiss Carbon dioxide in water and seawater: the solubility of a non-ideal gas , 1974 .

[55]  I. James,et al.  A fine-resolution 3D model of the Southern North Sea , 1996 .

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

[57]  F. Muller,et al.  Estimating the organic acid contribution to coastal seawater alkalinity by potentiometric titrations in a closed cell. , 2008, Analytica chimica acta.

[58]  R. Feely,et al.  Dissociation constants for carbonic acid determined from field measurements , 2002 .

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

[60]  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 .

[61]  R. Feely,et al.  Discrete water column measurements of CO2 fugacity and pHT in seawater: A comparison of direct measurements and thermodynamic calculations , 1998 .

[62]  J. Gattuso,et al.  Effect of ocean acidification on microbial diversity and on microbe-driven biogeochemistry and ecosystem functioning , 2010 .

[63]  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.

[64]  F. Millero Thermodynamics of the carbon dioxide system in the oceans , 1995 .

[65]  U. Riebesell,et al.  Marine ecosystem community carbon and nutrient uptake stoichiometry under varying ocean acidification during the PeECE III experiment , 2007 .

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

[67]  A. Dickson The carbon dioxide system in seawater : equilibrium chemistry and measurements 1 , 2011 .