Sensitivity of the Simulated Distributions of Water Masses, CFCs, and Bomb 14C to Parameterizations of Mesoscale Tracer Transports in a Model of the North Pacific

Yongfu Xu State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

Search for other papers by Yongfu Xu in
Current site
Google Scholar
PubMed
Close
,
Shigeaki Aoki National Institute of Advanced Industrial Sciences and Technology, Tsukuba, Ibaraki, Japan

Search for other papers by Shigeaki Aoki in
Current site
Google Scholar
PubMed
Close
, and
Koh Harada National Institute of Advanced Industrial Sciences and Technology, Tsukuba, Ibaraki, Japan

Search for other papers by Koh Harada in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

A basinwide ocean general circulation model of the North Pacific Ocean is used to study the sensitivity of the simulated distributions of water masses, chlorofluorocarbons (CFCs), and bomb carbon-14 isotope (14C) to parameterizations of mesoscale tracer transports. Five simulations are conducted, including a run with the traditional horizontal mixing scheme and four runs with the isopycnal transport parameterization of Gent and McWilliams (GM). The four GM runs use different values of isopycnal and skew diffusivities. Simulated results show that the GM mixing scheme can help to form North Pacific Intermediate Water (NPIW). Greater isopycnal diffusivity enhances formation of NPIW. Although greater skew diffusivity can also generate NPIW, it makes the subsurface too fresh. Results from simulations of CFC uptake show that greater isopycnal diffusivity generates the best results relative to observations in the western North Pacific. The model generally underestimates the inventories of CFCs in the western North Pacific. The results from simulations of bomb 14C reproduce some observed features. Greater isopycnal diffusivity generates a longitudinal gradient of the inventory of bomb 14C from west to east, whereas greater skew diffusivity makes it reversed. It is considered that the ratio of isopycnal diffusivity to skew diffusivity is important. An increase in isopycnal diffusivity increases storage of passive tracers in the subtropical gyre.

Corresponding author address: Yongfu Xu, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Email: xyf@mail.iap.ac.cn

Abstract

A basinwide ocean general circulation model of the North Pacific Ocean is used to study the sensitivity of the simulated distributions of water masses, chlorofluorocarbons (CFCs), and bomb carbon-14 isotope (14C) to parameterizations of mesoscale tracer transports. Five simulations are conducted, including a run with the traditional horizontal mixing scheme and four runs with the isopycnal transport parameterization of Gent and McWilliams (GM). The four GM runs use different values of isopycnal and skew diffusivities. Simulated results show that the GM mixing scheme can help to form North Pacific Intermediate Water (NPIW). Greater isopycnal diffusivity enhances formation of NPIW. Although greater skew diffusivity can also generate NPIW, it makes the subsurface too fresh. Results from simulations of CFC uptake show that greater isopycnal diffusivity generates the best results relative to observations in the western North Pacific. The model generally underestimates the inventories of CFCs in the western North Pacific. The results from simulations of bomb 14C reproduce some observed features. Greater isopycnal diffusivity generates a longitudinal gradient of the inventory of bomb 14C from west to east, whereas greater skew diffusivity makes it reversed. It is considered that the ratio of isopycnal diffusivity to skew diffusivity is important. An increase in isopycnal diffusivity increases storage of passive tracers in the subtropical gyre.

Corresponding author address: Yongfu Xu, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Email: xyf@mail.iap.ac.cn

Save
  • Broecker, W. S., T-H. Peng, H. G. Ostlund, and M. Stuiver, 1985: The distribution of bomb radiocarbon in the ocean. J. Geophys. Res, 90 , 69256939.

    • Search Google Scholar
    • Export Citation
  • Broecker, W. S., S. Sutherland, W. Smithie, T-H. Peng, and G. Ostlund, 1995: Oceanic radiocarbon: Separation of the bomb and natural components. Global Biogeochem. Cycles, 9 , 263288.

    • Search Google Scholar
    • Export Citation
  • Bryan, K., 1969: A numerical method for the study of the circulation of the World Ocean. J. Comput. Phys, 4 , 347376.

  • Craig, A. P., J. L. Bullister, D. E. Harrison, R. M. Chervin, and A. J. Semtner Jr., 1998: A comparison of temperature, salinity, and chlorofluorocarbon observations with results from a 1° resolution three-dimensional global ocean model. J. Geophys. Res, 103 , 10991119.

    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., and J. C. McWilliams, 1995: Sensitivity of the global ocean circulation to parameterizations of mesoscale tracer transports. J. Climate, 8 , 29672987.

    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., J. C. McWilliams, and P. R. Gent, 1994: The role of mesoscale tracer transport in the global ocean circulation. Science, 264 , 11231126.

    • Search Google Scholar
    • Export Citation
  • Dixon, K. W., J. L. Bullister, R. H. Gammon, and R. J. Stouffer, 1996: Examining a coupled climate model using CFC-11 as an ocean tracer. Geophys. Res. Lett, 23 , 19571960.

    • Search Google Scholar
    • Export Citation
  • Duffy, P. B., D. Eliason, A. J. Bourgeois, and C. Covey, 1995: Simulation of bomb radiocarbon in two ocean general circulation models. J. Geophys. Res, 100 , 2254522565.

    • Search Google Scholar
    • Export Citation
  • Duffy, P. B., K. Caldeira, J. Selvaggi, and M. I. Hoffert, 1997: Effects of subgrid-scale mixing parameterizations on simulated distributions of natural 14C, temperature, salinity in a three-dimensional ocean general circulation model. J. Phys. Oceanogr, 27 , 498524.

    • Search Google Scholar
    • Export Citation
  • England, M. H., 1995: Using chlorofluorocarbons to assess ocean climate models. Geophys. Res. Lett, 22 , 30513054.

  • England, M. H., and A. C. Hirst, 1997: Chlorofluorocarbon uptake in a world ocean model, 2. Sensitivity to surface thermohaline forcing and subsurface mixing parameterisations. J. Geophys. Res, 102 , 1570915731.

    • Search Google Scholar
    • Export Citation
  • England, M. H., and S. Rahmstorf, 1999: Sensitivity of ventilation rates and radiocarbon uptake to subgrid-scale mixing in ocean models. J. Phys. Oceanogr, 29 , 28022827.

    • Search Google Scholar
    • Export Citation
  • Follows, M. J., and J. C. Marshall, 1996: On models of bomb 14C in the North Atlantic. J. Geophys. Res, 101 , 2257722582.

  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr, 20 , 150155.

  • Gent, P. R., J. Willebrand, T. J. McDougall, and J. C. McWilliams, 1995: Parameterizing eddy-induced tracer transports in ocean circulation models. J. Phys. Oceanogr, 25 , 463474.

    • Search Google Scholar
    • Export Citation
  • Griffies, S. M., 2003: Fundamentals of Ocean Climate Models. Princeton University Press, 491 pp.

  • Hellerman, S., and M. Rosenstein, 1983: Normal monthly wind stress over the World Ocean with error estimates. J. Phys. Oceanogr, 13 , 10931104.

    • Search Google Scholar
    • Export Citation
  • Hirst, A. C., and T. J. McDougall, 1996: Deep-water properties and surface buoyancy flux as simulated by a z-coordinate model including eddy-induced advection. J. Phys. Oceanogr, 26 , 13201343.

    • Search Google Scholar
    • Export Citation
  • Jia, Y., and K. J. Richards, 1996: Tritium distributions in an isopycnic model of the North Atlantic. J. Geophys. Res, 101 , 1188311901.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., and T. P. Boyer, 1994: Temperature. Vol. 4, World Ocean Atlas 1994, NOAA Atlas NESDIS 4, 117 pp.

  • Levitus, S., R. Burgett, and T. P. Boyer, 1994: Salinity. Vol. 3, World Ocean Atlas 1994, NOAA Atlas NESDIS 3, 99 pp.

  • McDougall, T. J., A. C. Hirst, M. H. England, and P. C. McIntosh, 1996: Implications of a new eddy parameterization for ocean models. Geophys. Res. Lett, 23 , 20852088.

    • Search Google Scholar
    • Export Citation
  • Poulain, P. M., 1993: Estimates of horizontal divergence and vertical velocity in the equatorial Pacific. J. Phys. Oceanogr, 23 , 601607.

    • Search Google Scholar
    • Export Citation
  • Redi, M. H., 1982: Oceanic isopycnal mixing by coordinate rotation. J. Phys. Oceanogr, 12 , 11541158.

  • Robitaille, D. Y., and A. J. Weaver, 1995: Validation of sub-grid-scale mixing schemes using CFCs in a global ocean model. Geophys. Res. Lett, 22 , 29172920.

    • Search Google Scholar
    • Export Citation
  • Rodgers, K. B., and M. A. Cane, 1997: Seasonal variability of sea surface 14C in the equatorial Pacific in an ocean circulation model. J. Geophys. Res, 102 , 1862718639.

    • Search Google Scholar
    • Export Citation
  • Toggweiler, J. R., K. Dixon, and K. Bryan, 1989: Simulations of radiocarbon in a coarse-resolution world ocean model, 2, Distribution of bomb-produced 14C. J. Geophys. Res, 94 , 82438264.

    • Search Google Scholar
    • Export Citation
  • Walker, S. J., R. F. Weiss, and P. K. Salameh, 2000: Reconstructed histories of the annual mean atmospheric mole fractions for the halocarbons CFC-11, CFC-12, CFC-113, and carbon tetrachloride. J. Geophys. Res, 105 , 1428514296.

    • Search Google Scholar
    • Export Citation
  • Watanabe, Y. W., K. Harada, and K. Ishikawa, 1994: Chlorofluorocarbons in the central North Pacific and southward spreading time of North Pacific Intermediate Water. J. Geophys. Res, 99 , 2519525213.

    • Search Google Scholar
    • Export Citation
  • Watanabe, Y. W., A. Ishida, M. Tamaki, K. Okuda, and M. Fukasawa, 1997: Water column inventories of CFCs and production rate of intermediate water in the North Pacific. Deep-Sea Res, 44 , 10911104.

    • Search Google Scholar
    • Export Citation
  • Willey, D. A., R. A. Fine, R. E. Sonnerup, J. L. Bullister, W. M. Smethie Jr., and M. J. Warner, 2004: Global oceanic chlorofluorocarbon inventory. Geophys. Res. Lett, 31 .L01303, doi:10.1029/2003GL018816.

    • Search Google Scholar
    • Export Citation
  • Xu, Y., K. Nakata, A. Ishida, S. Aoki, and K. Harada, 1999: Simulations of chlorofluorocarbon uptake in a model of the North Pacific. J. Adv. Mar. Sci. Technol. Soc, 5 , 118.

    • Search Google Scholar
    • Export Citation
  • Xu, Y., Y. W. Watanabe, S. Aoki, and K. Harada, 2000: Simulations of storage of anthropogenic carbon dioxide in the North Pacific using an ocean general circulation model. Mar. Chem, 72 , 221238.

    • Search Google Scholar
    • Export Citation
  • Yamanaka, G., Y. Kitamura, and M. Endoh, 1998a: Formation of North Pacific Intermediate Water in MRI ocean general circulation model: 1. Subgrid-scale mixing and marginal sea fresh water. J. Geophys. Res, 103 , 3088530903.

    • Search Google Scholar
    • Export Citation
  • Yamanaka, G., Y. Kitamura, and M. Endoh, 1998b: Formation of North Pacific Intermediate Water in MRI ocean general circulation model, 2, Transient tracer experiments. J. Geophys. Res, 103 , 3090530921.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 198 33 4
PDF Downloads 35 11 0