Testing global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration

We present a method for testing the performance of global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration. We combine these measurements to define a tracer, atmospheric potential oxygen (APO ≈ O2 + CO2), which is conservative with respect to terrestrial photosynthesis and respiration. We then compare observations of APO to the simulations of an atmospheric transport model which uses ocean‐model air‐sea fluxes and fossil fuel combustion estimates as lower boundary conditions. We present observations of the annual‐average concentrations of CO2, O2, and APO at 10 stations in a north‐south transect. The observations of APO show a significant interhemispheric gradient decreasing towards the north. We use air‐sea CO2, O2, and N2 fluxes from the Princeton ocean biogeochemistry model, the Hamburg model of the ocean carbon cycle, and the Lawrence Livermore ocean biogeochemistry model to drive the TM2 atmospheric transport model. The latitudinal variations in annual‐average APO predicted by the combined models are distinctly different from the observations. All three models significantly underestimate the interhemispheric difference in APO, suggesting that they underestimate the net southward transport of the sum of O2 and CO2 in the oceans. Uncertainties in the model‐observation comparisons include uncertainties associated with the atmospheric measurements, the atmospheric transport model, and the physical and biological components of the ocean models. Potential deficiencies in the physical components of the ocean models, which have previously been suggested as causes for anomalously large heat fluxes out of the Southern Ocean, may contribute to the discrepancies with the APO observations. These deficiencies include the inadequate parameterization of subgrid‐scale isopycnal eddy mixing, a lack of subgrid‐scale vertical convection, too much Antarctic sea‐ice formation, and an overestimation of vertical diffusivities in the main thermocline.

[1]  N. Gruber.  Anthropogenic CO2 in the Atlantic Ocean , 1998 .

[2]  Scott C. Doney,et al.  Seasonal variations in the atmospheric O2/N2 ratio in relation to the kinetics of air‐sea gas exchange , 1998 .

[3]  A. Manning,et al.  Methods for measuring changes in atmospheric O2 concentration and their application in southern hemisphere air , 1998 .

[4]  Philip B. Duffy,et al.  Effects of Subgrid-Scale Mixing Parameterizations on Simulated Distributions of Natural 14C, Temperature, and Salinity in a Three-Dimensional Ocean General Circulation Model , 1997 .

[5]  Katharina D. Six,et al.  Effects of plankton dynamics on seasonal carbon fluxes in an ocean general circulation model , 1996 .

[6]  T. Stocker,et al.  An improved method for detecting anthropogenic CO2 in the oceans , 1996 .

[7]  Jorge L. Sarmiento,et al.  Oceanic Carbon Dioxide Uptake in a Model of Century-Scale Global Warming , 1996, Science.

[8]  E. Maier‐Reimer,et al.  Future ocean uptake of CO2: interaction between ocean circulation and biology , 1996 .

[9]  M. England,et al.  Implications of a new eddy parameterization for ocean models , 1996 .

[10]  Philip J. Rasch,et al.  The seasonal cycle of atmospheric CO2: A study based on the NCAR Community Climate Model (CCM2) , 1996 .

[11]  Martin Heimann,et al.  Global and hemispheric CO2 sinks deduced from changes in atmospheric O2 concentration , 1996, Nature.

[12]  E. Maier‐Reimer,et al.  On the relations between the oceanic uptake of CO2 and its carbon isotopes , 1996 .

[13]  J. Severinghaus.  Studies of the terrestrial O{sub 2} and carbon cycles in sand dune gases and in biosphere 2 , 1995 .

[14]  L. A. Anderson,et al.  Global ocean phosphate and oxygen simulations , 1995 .

[15]  J. Toggweiler,et al.  Effect of Sea Ice on the Salinity of Antarctic Bottom Waters , 1995 .

[16]  R. Keeling,et al.  TRANSPORT OF HEAT, CO2 AND O2 BY THE ATLANTIC'S THERMOHALINE CIRCULATION , 1995 .

[17]  Corinne Le Quéré,et al.  AIR-SEA CO2 TRANSFER AND THE CARBON BUDGET OF THE NORTH ATLANTIC , 1995 .

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

[19]  Frank O. Bryan,et al.  An Overlooked Problem in Model Simulations of the Thermohaline Circulation and Heat Transport in the Atlantic Ocean , 1995 .

[20]  Ian G. Enting,et al.  A synthesis inversion of the concentration and δ 13 C of atmospheric CO 2 , 1995 .

[21]  Gregg Marland,et al.  The Carbon Cycle: Carbon Dioxide Emissions from Fossil Fuel Consumption and Cement Manufacture, 1751–1991, and an Estimate of Their Isotopic Composition and Latitudinal Distribution , 1994 .

[22]  G. Danabasoglu,et al.  The Role of Mesoscale Tracer Transports in the Global Ocean Circulation , 1994, Science.

[23]  E. Dlugokencky,et al.  Correction to "A dramatic decrease in the growth rate of atmospheric methane in the northern hemisphere during 1992" by E. J. Dlugokencky, K. A. Masarie, P.M. Lang, P. P. Tans, , 1994 .

[24]  David J. Webb,et al.  The Deacon Cell and the other meridional cells of the Southern ocean , 1994 .

[25]  E. Maier‐Reimer,et al.  Geochemical cycles in an Ocean General Circulation Model , 1993 .

[26]  J. Toggweiler,et al.  A seasonal three‐dimensional ecosystem model of nitrogen cycling in the North Atlantic Euphotic Zone , 1993 .

[27]  Klaus Hasselmann,et al.  Mean Circulation of the Hamburg LSG OGCM and Its Sensitivity to the Thermohaline Surface Forcing , 1993 .

[28]  P. Tans,et al.  What atmospheric oxygen measurements can tell us about the global carbon cycle , 1993 .

[29]  Pieter P. Tans,et al.  Mixing ratios of carbon monoxide in the troposphere , 1992 .

[30]  R. Law,et al.  APPLICATION OF AN ATMOSPHERIC TRACER MODEL TO HIGH SOUTHERN LATITUDES , 1992 .

[31]  Ralph F. Keeling,et al.  Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle , 1992, Nature.

[32]  W. Broecker,et al.  Interhemispheric transport of carbon dioxide by ocean circulation , 1992, Nature.

[33]  J. Toggweiler,et al.  Downward transport and fate of organic matter in the ocean: Simulations with a general circulation model , 1992 .

[34]  Syukuro Manabe,et al.  Transient responses of a coupled ocean-atmosphere model to gradual changes of atmospheric CO2 , 1991 .

[35]  E. Maier‐Reimer,et al.  Dissolved organic carbon in modeling oceanic new production , 1991 .

[36]  I. Fung,et al.  Observational Contrains on the Global Atmospheric Co2 Budget , 1990, Science.

[37]  D. Dyrssen,et al.  Carbon Dioxide Transport by Ocean Currents at 25�N Latitude in the Atlantic Ocean , 1989, Science.

[38]  J. Toggweiler,et al.  Simulations of radiocarbon in a coarse-resolution world ocean model: 2. Distributions of bomb-produced carbon 14 , 1989 .

[39]  Keith W. Dixon,et al.  Simulations of radiocarbon in a coarse-resolution world ocean model: 1. Steady state prebomb distributions , 1989 .

[40]  I. Enting,et al.  Seasonal sources and sinks of atmospheric CO2 Direct inversion of filtered data , 1989 .

[41]  J. Toggweiler,et al.  Ocean carbon-cycle dynamics and atmospheric Pco2 , 1988, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[42]  G. Marland,et al.  CO2 from fossil fuel burning: global distribution of emissions , 1985 .

[43]  C. Wunsch,et al.  Mass, Heat, Salt and Nutrient Fluxes in the South Pacific Ocean , 1983 .

[44]  S. Levitus.  Climatological Atlas of the World Ocean , 1982 .

[45]  T. Stocker,et al.  An improved method for detecting anthropogenic CO 2 in the oceans , 1997 .

[46]  Martin Heimann,et al.  The global atmospheric tracer model TM3 , 1995 .

[47]  J. Toggweiler,et al.  New Radiocarbon Constraints on the Upwelling of Abyssal Water to the Ocean’s Surface , 1993 .

[48]  Wallace Broeker,et al.  The Great Ocean Conveyor , 1991 .

[49]  P. Gent,et al.  Isopycnal mixing in ocean circulation models , 1990 .

[50]  R. Keeling.  Development of an interferometric oxygen analyzer for precise measurement of the atmospheric O[2] mole fraction , 1988 .