Impact of Geoid Improvement on Ocean Mass and Heat Transport Estimates

  • P. Le Grand
Part of the Space Sciences Series of ISSI book series (SSSI, volume 17)


One long-standing difficulty in estimating the large-scale ocean circulation is the inability lo observe absolute current velocities. Both conventional hydrographic measurements and altimetric measurements provide observations of currents relative to an unknown velocity at a reference depth in the case of hydrographic data, and relative to mean currents calculated over some averaging period in the case of altimetric data. Space gravity missions together with altimetric observations have the potential to overcome this difficulty by providing absolute estimates of the velocity of surface oceanic currents. The absolute surface velocity estimates will in turn provide the reference level velocities that are necessary to compute absolute velocities at any depth level from hydrographic data.

Several studies have been carried out to quantify the improvements expected from ongoing and future space gravity missions. The resuhs of these studies in terms of volume flux estimates (transport of water masses) and heat flux estimates (transport of heat by the ocean) are reviewed in this paper. The studies are based on ocean inverse modeling techniques that derive impact estimates solely from the geoid error budgets of forthcoming space gravity missions. Despite some differences in ihe assumptions made, the inverse modeling calculations all point lo significant improvements in estimates of oceanic fluxes. These improvements, measured in terms of reductions of uncertainties, arc expected to be as large as a factor of 2.

New developments in autonomous ocean observing systems will complement the developments expected from space gravity missions. The synergies of in situ and satellite observing systems are considered in the conclusion of this paper.


Ocean Circulation Volume Transport Altimetric Data Geoid Height Hydrographic Data 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. Coachman, L.K., and K. Aagaard: 1988, ‘Transports through the Bering Strait: Annual and interannual variability’, J. Geophys. Res. 93. 15,535–15,539.Google Scholar
  2. Fofonoff, N.P.: 1985. ‘Physical properties of seawaler: new salinity scale and equation of stale for seawaier’. J. Geopliys. Res. 9. 3.332–3,342.Google Scholar
  3. IPCC Third Assessment Report: 2001. ‘Climate Change 2001: The Scientific Basis, Contribution of Working Group 1 to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC)’, J. T. Houghton. Y. Ding. D.J. Griggs. M. Noguer. P. J. van der Linden and D. Xiaosu (Eds.). Cambridge University Press. UK. pp 944.Google Scholar
  4. Ganachaud. A., and C. Wunsch: 2000. •Improved estimates of global ocean circulation, heal transport and mixing from hydrographic data’. Nature 408. 453–457.Google Scholar
  5. Ganachaud. A.. C. Wunsch. M.-C. Kim. and B. Tapley: 1997. ‘Combination of TOPEX/Poseidon data with a hydrographic inversion for determination of the oceanic general circulation and its relation togeoid accuracy“. Geophys. J. Int. 128. 708–722.Google Scholar
  6. Hall. M.M., and H.L. Bryden: 1982. “Direct estimates and mechanisms of ocean heal transport”. Deep-Sea Res. 29. 339–359.Google Scholar
  7. LeGrand. P.. H. Mercier. and T. Reynaud: 1998. ‘Combining T/P altimetric data with hydrographic data to estimate the mean dynamic topography of the North Atlantic and improve the geoid“. Ann. Geophys. 16. 638–650.Google Scholar
  8. LeGrand. P.: 2001, ‘Impact of the Gravity Field and Steady-Stale Ocean Circulation Explorer (GOCE) mission on ocean circulation estimates. Volume fluxes in a climatological inverse model of the Atlantic“. J. Geophys. Res. 106, 19,597–19,610.Google Scholar
  9. LeGrand. P.. E.J.O. Schrama. and J. Tournadre: 2002. ‘An inverse modeling estimate of the dynamic-topography of the ocean“, Geophys. Res. Letters, 30(2), 34–1, Cite ID 1062, DOI 10.I029/2002GL0149I7Google Scholar
  10. Lemoine. F.G.. S.C. Kenyon, J.K. Factor. R.G. Trimmer. N.K. Pavlis. D.S. Chinn. C.M. Cox. S.M. Klosko. S.B. Luthcke, M.H. Torrence. Y.M. Wang., R.G. Wiliamson, E.C. Pavlis, R.H. Rapp. and T.R. Olson: 1998. “The development of the joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) geopotenlial model EGM96’,: NASA Technical Publication. NASA Technical Publication NASA, Center for Aerospace Information. Hanover, MD.Google Scholar
  11. MillilT. R.F.. M.H. Freilich. W.T. Liu, R. Atlas, and W.G. Large: 2001, ‘Global ocean surface vector wind observations from space“. Observing the Oceans in the 21st Century, p 102–119. C.J Koblinsky and N.R. Smith (Eds.). GODAE Project Office and Bureau of Meteorology, Melbourne.Google Scholar
  12. Pond. S.. and G.L. Pickard: 1983. “Introductory dynamical oceanography”. 329 pp. Pergamon Press. Oxford.Google Scholar
  13. Schröter. J.. M. Losch, and B. Sloyan: 2002, ‘Impact of the Gravity Field and Steady–State Ocean Circulation Explorer (GOCE) mission on ocean circulation estimates 2. Volume and heat fluxes across hydrographic sections of unequally spaced stations’, J. Geophys. Res. 107. 4–1–4–20.Google Scholar
  14. Sigman. D.M.. and E.A. Boyle: 2000. “Glacial/interglacial variations in atmospheric carbon dioxide”. Nature 407. 171–174.CrossRefGoogle Scholar
  15. Wunsch. C.: 1978, ‘The North Atlantic general circulation west of 50W determined by inverse methods’, Revs. Geophys. and Space Pltys. 16. 583–620CrossRefGoogle Scholar
  16. Wunsch, C: 1984, ‘An eclectic Atlantic Ocean circulation model. Part E The meridional flux ol“ heat’, J. Phys. Oc. 15,1521–1531. Wunsch, C.: 1996, ’ The Ocean Circulation Inverse Problem’. 422 pp., Cambridge Univ. Press. New York.Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2003

Authors and Affiliations

  • P. Le Grand
    • 1
  1. 1.IFREMER, BP 70PlouzaneFrance

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