Oceanic signals in observed motions of the Earth's pole of rotation

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Motion of the Earth's pole of rotation relative to its crust, commonly referred to as polar motion, can be excited by a variety of geophysical mechanisms1. In particular, changes in atmospheric wind and mass fields have been linked to polar motion over a wide range of timescales, but substantial discrepancies remain between the atmospheric and geodetic observations1,2,3,4. Here we present results from a nearly global ocean model which indicate that oceanic circulation and mass-field variability play important roles in the excitation of seasonal to fortnightly polar motion. The joint oceanic and atmospheric excitation provides a better agreement with the observed polar motion than atmospheric excitation alone. Geodetic measurements may therefore be used to provide a global consistency check on the quality of simulated large-scale oceanic fields.

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Figure 1: Five-day averaged values of χ1O and χ2O for the period January 85–April 96.
Figure 2: Power spectral density for oceanic χ1P (solid line), χ1V (dotted), χ2P (dashed) and χ2V (dotted-dashed) calculated by averaging respective periodograms over 20 adjacent frequencies.
Figure 3: Assessment of oceanic effects on the excitation of polar motion.


  1. 1

    Eubanks, T. M. in Contributions of Space Geodesy to Geodynamics: Earth Dynamics 1–54 (eds Smith, D. & Turcotte, D.) (AGU Monogr., Geodynamics Ser., Vol. 24, Am. Geophys. Un., Washington DC, 1993).

  2. 2

    Eubanks, T. M., Steppe, J. A., Dickey, J. O., Rosen, R. D. & Salstein, D. A. Causes of rapid motions of the Earth's pole. Nature 334, 115–119 (1988).

  3. 3

    Gross, R. S. & Lindqwister, U. J. Atmospheric excitation of polar motion during the GIG '91 measurement campaign. Geophys. Res. Lett. 19, 849–852 (1992).

  4. 4

    Chao, B. F. Excitation of Earth's polar motion by atmospheric angular momentum variations, 1980–1990. Geophys. Res. Lett. 20, 253–256 (1993).

  5. 5

    Barnes, R. T. H., Hide, R., White, A. A. & Wilson, C. A. Atmospheric angular momentum fluctuations, length-of-day changes and polar motion. Proc. R. Soc. Lond. A 387, 31–73 (1983).

  6. 6

    Wilson, C. R. & Haubrich, R. A. Meteorological excitation of the Earth's wobble. Geophys. J. R. Astron. Soc. 46, 707–743 (1976).

  7. 7

    Wahr, J. M. The effects of the atmosphere and oceans on the Earth's wobble and on the seasonal variation in the length of day — II. Results. Geophys. J. R. Astron. Soc. 74, 451–487 (1983).

  8. 8

    Salstein, D. A., Ponte, R. M., Rosen, R. D. & Cady-Pereira, K. Angular momentum in a free-surface ocean general circulation model. Eos (Spring Meeting Suppl.) 76, 82 (1995).

  9. 9

    Bryan, F. O. & Smith, R. D. Oceanic excitation of variations in Earth rotation from a high resolution global model. Eos (Fall Meeting Suppl.) 76, 61 (1995).

  10. 10

    Ponte, R. M. Oceanic excitation of daily to seasonal signals in Earth rotation: results from a constant-density numerical model. Geophys. J. Int. 130, 469–474 (1997).

  11. 11

    Marshall, J., Adcroft, A., Hill, C., Perelman, L. & Heisey, C. Afinite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers. J. Geophys. Res. 102, 5753–5766 (1997).

  12. 12

    Marshall, J., Hill, C., Perelman, L. & Adcroft, A. Hydrostatic, quasi-hydrostatic and non-hydrostatic ocean modeling. J. Geophys. Res. 102, 5733–5752 (1997).

  13. 13

    Levitus, S., Burgett, R. & Boyer, T. World Ocean Atlas 1994 Vol. 3, Salinityand Vol. 4,Temperature (NOAA Atlas NESDIS 3 and 4, US Dept of Commerce, Washington DC, 1994).

  14. 14

    Barnier, B., Siefridt, L. & Marchesiello, P. Thermal forcing for a global ocean circulation model using a three-year climatology of ECMWF analyses. J. Mar. Sys. 6, 363–380 (1995).

  15. 15

    Jayne, S. & Marotzke, J. Adestabilizing thermohaline circulation — atmosphere — sea ice feedback. J.Clim. (submitted).

  16. 16

    Stammer, D.et al. The Global Ocean Circulation Estimated from TOPEX/POSEIDON Altimetry and the MIT General Circulation Model (Rep. 49, MIT Center of Global Change Science, Cambridge, 1997).

  17. 17

    Greatbatch, R. J. Anote on the representation of steric sea level in models that conserve volume rather than mass. J. Geophys. Res. 99, 12767–12771 (1994).

  18. 18

    Salstein, D. A., Kann, D. M., Miller, A. J. & Rosen, R. D. The sub-bureau for atmospheric angular momentum of the international earth rotation service: a meteorological data center with geodetic applications. Bull. Am. Meteor. Soc. 74, 67–80 (1993).

  19. 19

    Wilson, C. R. Discrete polar motion equations. Geophys. J. R. Astron. Soc. 80, 551–554 (1985).

  20. 20

    Salstein, D. A. Monitoring atmospheric winds and pressures for Earth orientation studies. Adv. Space Res. 13, 11175–11184 (1993).

  21. 21

    Salstein, D. A. & Rosen, R. D. in Proc. 7th Conf. on Climate Variations 344–348 (Am. Meteorol. Soc., Boston, 1997).

  22. 22

    Rosen, R. D. The axial momentum balance of Earth and its fluid envelope. Surv. Geophys. 14, 1–29 (1993).

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We thank D. Spiegel for help with the computation, and F. Bryan, B. Chao, R. Rosen and D. Salstein for comments. This work was supported by NASA's Mission to Planet Earth.

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Correspondence to Rui M. Ponte.

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