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  • Adjoint method  (1)
  • Air-sea CO2 exchange  (1)
  • Biogeochemical cycles  (1)
  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): C12020, doi:10.1029/2011JC006998.
    Description: A three dimensional model of Arctic Ocean circulation and mixing, with a horizontal resolution of 18 km, is overlain by a biogeochemical model resolving the physical, chemical and biological transport and transformations of phosphorus, alkalinity, oxygen and carbon, including the air-sea exchange of dissolved gases and the riverine delivery of dissolved organic carbon. The model qualitatively captures the observed regional and seasonal trends in surface ocean PO4, dissolved inorganic carbon, total alkalinity, and pCO2. Integrated annually, over the basin, the model suggests a net annual uptake of 59 Tg C a−1, within the range of published estimates based on the extrapolation of local observations (20–199 Tg C a−1). This flux is attributable to the cooling (increasing solubility) of waters moving into the basin, mainly from the subpolar North Atlantic. The air-sea flux is regulated seasonally and regionally by sea-ice cover, which modulates both air-sea gas transfer and the photosynthetic production of organic matter, and by the delivery of riverine dissolved organic carbon (RDOC), which drive the regional contrasts in pCO2 between Eurasian and North American coastal waters. Integrated over the basin, the delivery and remineralization of RDOC reduces the net oceanic CO2 uptake by ~10%.
    Description: This study has been carried out as part of ECCO2 and SASS (Synthesis of the Arctic System Science) projects funded by NASA and NSF, respectively. MM and MJF are grateful for support from the National Science Foundation (ARC-0531119 and ARC-0806229) for financial support. MM also acknowledges NASA for providing computer time, the use of the computing facilities at NAS center and also the Scripps post-doctoral program for further financial support that helped to complete the manuscript. RMK also acknowledges NOAA for support (NA08OAR4310820 and NA08OAR4320752).
    Description: 2012-06-15
    Keywords: Air-sea gas exchange ; Biogeochemical cycles ; Land-ocean coupling ; Numerical modeling ; Ocean carbon cycle ; Polar oceans
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 21 (2007): , doi:10.1029/2006GB002751.
    Description: We use an inverse method to estimate the global-scale pattern of the air-sea flux of natural CO2, i.e., the component of the CO2 flux due to the natural carbon cycle that already existed in preindustrial times, on the basis of ocean interior observations of dissolved inorganic carbon (DIC) and other tracers, from which we estimate ΔC gasex , i.e., the component of the observed DIC that is due to the gas exchange of natural CO2. We employ a suite of 10 different Ocean General Circulation Models (OGCMs) to quantify the error arising from uncertainties in the modeled transport required to link the interior ocean observations to the surface fluxes. The results from the contributing OGCMs are weighted using a model skill score based on a comparison of each model's simulated natural radiocarbon with observations. We find a pattern of air-sea flux of natural CO2 characterized by outgassing in the Southern Ocean between 44°S and 59°S, vigorous uptake at midlatitudes of both hemispheres, and strong outgassing in the tropics. In the Northern Hemisphere and the tropics, the inverse estimates generally agree closely with the natural CO2 flux results from forward simulations of coupled OGCM-biogeochemistry models undertaken as part of the second phase of the Ocean Carbon Model Intercomparison Project (OCMIP-2). The OCMIP-2 simulations find far less air-sea exchange than the inversion south of 20°S, but more recent forward OGCM studies are in better agreement with the inverse estimates in the Southern Hemisphere. The strong source and sink pattern south of 20°S was not apparent in an earlier inversion study, because the choice of region boundaries led to a partial cancellation of the sources and sinks. We show that the inversely estimated flux pattern is clearly traceable to gradients in the observed ΔC gasex , and that it is relatively insensitive to the choice of OGCM or potential biases in ΔC gasex . Our inverse estimates imply a southward interhemispheric transport of 0.31 ± 0.02 Pg C yr−1, most of which occurs in the Atlantic. This is considerably smaller than the 1 Pg C yr−1 of Northern Hemisphere uptake that has been inferred from atmospheric CO2 observations during the 1980s and 1990s, which supports the hypothesis of a Northern Hemisphere terrestrial sink.
    Description: This research was financially supported by the National Aeronautics and Space Administration under grant NAG5-12528. N. G. also acknowledges support by the National Science Foundation (OCE-0137274). Climate and Environmental Physics, Bern, acknowledges support by the European Union through the Integrated Project CarboOcean and the Swiss National Science Foundation.
    Keywords: Air-sea CO2 exchange ; Natural carbon cycle ; Ocean inversion
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Format: text/plain
    Format: application/postscript
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Heimbach, P., Fukumori, I., Hills, C. N., Ponte, R. M., Stammer, D., Wunsch, C., Campin, J., Cornuelle, B., Fenty, I., Forget, G., Koehl, A., Mazloff, M., Menemenlis, D., Nguyen, A. T., Piecuch, C., Trossman, D., Verdy, A., Wang, O., & Zhang, H. Putting it all together: Adding value to the global ocean and climate observing systems with complete self-consistent ocean state and parameter estimates. Frontiers in Marine Science, 6 (2019):55, doi:10.3389/fmars.2019.00055.
    Description: In 1999, the consortium on Estimating the Circulation and Climate of the Ocean (ECCO) set out to synthesize the hydrographic data collected by the World Ocean Circulation Experiment (WOCE) and the satellite sea surface height measurements into a complete and coherent description of the ocean, afforded by an ocean general circulation model. Twenty years later, the versatility of ECCO's estimation framework enables the production of global and regional ocean and sea-ice state estimates, that incorporate not only the initial suite of data and its successors, but nearly all data streams available today. New observations include measurements from Argo floats, marine mammal-based hydrography, satellite retrievals of ocean bottom pressure and sea surface salinity, as well as ice-tethered profiled data in polar regions. The framework also produces improved estimates of uncertain inputs, including initial conditions, surface atmospheric state variables, and mixing parameters. The freely available state estimates and related efforts are property-conserving, allowing closed budget calculations that are a requisite to detect, quantify, and understand the evolution of climate-relevant signals, as mandated by the Coupled Model Intercomparison Project Phase 6 (CMIP6) protocol. The solutions can be reproduced by users through provision of the underlying modeling and assimilation machinery. Regional efforts have spun off that offer increased spatial resolution to better resolve relevant processes. Emerging foci of ECCO are on a global sea level changes, in particular contributions from polar ice sheets, and the increased use of biogeochemical and ecosystem data to constrain global cycles of carbon, nitrogen and oxygen. Challenges in the coming decade include provision of uncertainties, informing observing system design, globally increased resolution, and moving toward a coupled Earth system estimation with consistent momentum, heat and freshwater fluxes between the ocean, atmosphere, cryosphere and land.
    Description: Major support for ECCO is provided by NASA's Physical Oceanography program via a contract to JPL/Caltech, with additional support through NASA's Modeling, Analysis and Prediction program, the Cryosphere Science program, and the Computational Modeling and Cyberinfrastructure program. Supplemental funding was obtained throughout the years via standard grants to individual team members from NSF, NOAA, and ONR.
    Keywords: ECCO ; Global ocean inverse modeling ; Optimal state and parameter estimation ; Adjoint method ; Ocean observations ; Coupled Earth system data assimilation ; Ocean reanalysis ; Global ocean circulation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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