Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Published:https://doi.org/10.1098/rsta.2006.1751

    The Earth's gravity field plays a central role in sea-level change. In the simplest application a precise gravity field will enable oceanographers to capitalize fully on the altimetric datasets collected over the past decade or more by providing a geoid from which absolute sea-level topography can be recovered. However, the concept of a static gravity field is now redundant as we can observe temporal variability in the geoid due to mass redistribution in or on the total Earth system. Temporal variability, associated with interactions between the land, oceans and atmosphere, can be investigated through mass redistributions with, for example, flow of water from the land being balanced by an increase in ocean mass. Furthermore, as ocean transport is an important contributor to the mass redistribution the time varying gravity field can also be used to validate Global Ocean Circulation models.

    This paper will review the recent history of static and temporal gravity field recovery, from the 1980s to the present day. In particular, mention will be made of the role of satellite laser ranging and other space tracking techniques, satellite altimetry and in situ gravity which formed the basis of gravity field determination until the last few years. With the launch of Challenging Microsatellite Payload and Gravity and Circulation Experiment (GRACE) our knowledge of the spatial distribution of the Earth's gravity field is taking a leap forward. Furthermore, GRACE is now providing insight into temporal variability through ‘monthly’ gravity field solutions. Prior to this data we relied on satellite tracking, Global Positioning System and geophysical models to give us insight into the temporal variability. We will consider results from these methodologies and compare them to preliminary results from the GRACE mission.

    References

    • Bettadpur, S. 2004a Level-2 gravity field product user handbook. GRACE 327–734, CSR, University of Texas at Austin. Google Scholar
    • Bettadpur, S. 2004b UTCSR level-2 processing standards document. GRACE 327–742, CSR, University of Texas at Austin. Google Scholar
    • Biancale R, et al. 2000 A new global Earth's gravity field model from satellite orbit perturbations: GRIM5-S1. Geophys. Res. Lett. 27, 3611–3614.doi:10.1029/2000GL011721. . Crossref, ISIGoogle Scholar
    • Blewitt G, Lavallée D, Clarke P.J& Nurutdinov K . 2001 A new global mode of Earth deformation: seasonal cycle detected. Science. 294, 2342–2345.doi:10.1126/science.1065328. . Crossref, PubMed, ISIGoogle Scholar
    • Chao B.F, Au A.Y, Boy J.P& Cox C.M . 2003 Time-variable gravity signal of an anomalous redistribution of water mass in the extratropic Pacific during 1998–2002. Geochem. Geophys. Geosyst. 4, (art. no. 1096) doi:10.1029/2003GC000589. . ISIGoogle Scholar
    • Chen J.L& Wilson C.R . 2003 Low degree gravitational changes from Earth rotation and geophysical models. Geophys. Res. Lett. 30, 2257–2260.doi:10.1029/2003GL018688. . Crossref, ISIGoogle Scholar
    • Chen J.L, Wilson C.R, Eanes R.J& Tapley B.D . 2000 A new assessment of long-wavelength gravitational variations. J. Geophys. Res. 105, 16 271–16 277.doi:10.1029/2000JB900115. . Crossref, ISIGoogle Scholar
    • Cheng M& Tapley B.D . 1999 Seasonal variations in low degree zonal harmonics of the Earth's gravity field from satellite laser ranging observations. J. Geophys. Res. 104, 2667–2681.doi:10.1029/1998JB900036. . Crossref, ISIGoogle Scholar
    • Cheng M, Shum C.K& Tapley B.D . 1997 Determination of long-term changes in the Earth's gravity field from satellite laser ranging observations. J. Geophys. Res. 102, 22 377–22 390.doi:10.1029/97JB01740. . Crossref, ISIGoogle Scholar
    • Cox C& Chao B.F . 2002 Detection of large-scale mass redistribution in the terrestrial system since 1998. Science. 297, 831 doi:10.1126/science.1072188. . Crossref, PubMed, ISIGoogle Scholar
    • Crétaux J.-F, Soudarin L, Davidson F.J.M, Gennero M.C, Bergé-Nguyen M& Cazenave A . 2002 Seasonal and interannual geocenter motion from SLR and DORIS measurements: comparison with surface loading data. J. Geophys. Res. 107, 2374 doi:10.1029/2002JB001820. . Crossref, ISIGoogle Scholar
    • Dickey J.O, Marcus S.L, de Viron O& Fukumori I . 2002 Recent Earth oblateness variations: unraveling climate and postglacial rebound effects. Science. 298, 1975–1977.doi:10.1126/science.1077777. . Crossref, PubMed, ISIGoogle Scholar
    • Dong D, Gross R.S& Dickey J.O . 1996 Seasonal variations of the Earth's gravitational field: an analysis of atmospheric pressure, ocean tidal, and surface water excitation. Geophys. Res. Lett. 23, 725–728.doi:10.1029/96GL00740. . Crossref, ISIGoogle Scholar
    • Farrell W.E . 1972 Deformation of the Earth by surface loading. Rev. Geophys. 10, 761–797. Crossref, ISIGoogle Scholar
    • Flechtner F AOD1B product description document. GRACE 327-750 2003 Potsdam:GeoForschungsZentrum. Google Scholar
    • Gross R.S, Blewitt G, Clarke P.J& Lavallée D . 2004 Degree-2 harmonics of the Earth's mass load estimated from GPS and Earth rotation data. Geophys. Res. Lett. 30, doi:10.1029/2004GL019589. . Google Scholar
    • Han S.C, Jekeli C& Shum C.K . 2004 Time-variable aliasing effects of ocean tides, atmosphere, and continental water mass on monthly mean GRACE gravity field. J. Geophys. Res. 109, doi:2003JB002501/B04403. . Crossref, ISIGoogle Scholar
    • Hendrick J.R, Leben R.R, Born G.H& Koblinsky C.J . 1996 Empirical orthogonal function analysis of global TOPEX/Poseidon altimeter data and implications for detection of global sea level rise. J. Geophys. Res. 101, 14 131–14 145.doi:10.1029/96JC00922. . Crossref, ISIGoogle Scholar
    • Knudsen P . 2003 Oceantides in GRACE monthly averaged gravity fields. Space Sci. Rev. 108, 261–270.doi:10.1023/A:1026215124036. . Crossref, ISIGoogle Scholar
    • Le Grand P . 2003 Impact of geoid improvements on ocean mass and heat transport estimates. Space Sci. Rev. 108, 225–238.doi:10.1023/A:1026263022219. . Crossref, ISIGoogle Scholar
    • Lemoine, F. G. et al. 1998 The development of the NASA GSFC and NIMA joint geopotential model. In Proc. Int. Symp. on Gravity, Geoid and Marine Geodesy GRAGEOMAR, Tokyo, Japan, October 1996. Google Scholar
    • Lerch F.J, Klosko S.M, Patel G.B& Wagner C.A . 1985 A gravity model for crustal dynamics (GEM-L2). J. Geophys. Res. 90, 9301–9311. Crossref, ISIGoogle Scholar
    • Levitus S& Boyer T World Ocean Atlas 1994. vol. 4: Temperature 1994 Washington, DC:US Department of Commerce. Google Scholar
    • Marsh J.G, et al. 1988 A new gravitational model for the Earth from satellite tracking data: GEMT1. J. Geophys. Res. 93, 6169–6215. Crossref, ISIGoogle Scholar
    • Moore P& Wang J . 2003 Geocentre variation from laser tracking of Lageos1/2 and loading data. Adv. Space Res. 31, 1927–1933.doi:10.1016/S0273-1177(03)00170-4. . Crossref, ISIGoogle Scholar
    • Moore, P., Zhang, Q. & Alothman, A. 2004 Temporal gravity field variability from a combination solution using SLR, CHAMP and GPS: comparisons with GRACE. Paper presented at First Joint Meeting of the CHAMP and GRACE science teams, July 2004, GeoForschungsZentrum (GFZ), Potsdam. Google Scholar
    • Moore P, Zhang Q& Alothman A . 2005 Annual and semi-annual variations of the earth's gravitational field from satellite laser ranging and CHAMP. J. Geophys. Res. 110, B06401 doi:10.1029/2004JB003448. . Crossref, ISIGoogle Scholar
    • Nerem R.S, Chao B.F, Au A.Y, Chan J.C, Klosko S.M, Pavlis N.K& Williamson R.G . 1993 Temporal variations of the Earth's gravitational field from satellite laser ranging to Lageos. Geophys. Res. Lett. 20, 595–598. Crossref, ISIGoogle Scholar
    • Nerem R.S, Lerch F.J, Klosko S.M, Patel G.B, Williamson R.G& Koblinsky C.J Ocean dynamic topography from satellite altimetry based on the GEM-T3 gravity model. Manuscr. Geodaet. 19, 1994a 346–366. Google Scholar
    • Nerem R.S, et al. Gravity model development for TOPEX/Poseidon: joint gravity models 1 and 2. J. Geophys. Res. 99, 1994b 24 421–24 447.doi:10.1029/94JC01376. . Crossref, ISIGoogle Scholar
    • Nerem R.S, Eanes R.J, Thompson P.F& Chen J.L . 2000 Observations of annual variations of the Earth's gravitational field using satellite laser ranging and geophysical models. Geophys. Res. Lett. 27, 1783–1786.doi:10.1029/1999GL008440. . Crossref, ISIGoogle Scholar
    • Nerem R.S, Wahr J.M& Leuliette E.W . 2003 Measuring the distribution of ocean mass from GRACE. Space Sci. Rev. 108, 331–344.doi:10.1023/A:1026275310832. . Crossref, ISIGoogle Scholar
    • Penna N.T& Stewart M.P . 2003 Aliased tidal signatures in continuous GPS height time series. Geophys. Res. Lett. 30, doi:10.1029/2003GL018828. . Crossref, ISIGoogle Scholar
    • Reigber Ch, Luehr H& Schwintzer P . 2002 CHAMP mission status. Adv. Space Res. 30, 129–134.doi:10.1016/S0273-1177(02)00276-4. . Crossref, ISIGoogle Scholar
    • Reigber Ch, et al. Earth gravity field and seasonal variability from CHAMP. Earth observation with CHAMP—results from three years in orbit , Reigber Ch, Lühr H, Schwintzer P& Wickert J . 2004pp. 25–30. Eds. Berlin:Springer. Google Scholar
    • Schrama E.J.O . 2003 Error characteristics estimated from CHAMP, GRACE and GOCE derived geoids and from satellite altimetry derived mean dynamic topography. Space Sci. Rev. 108, 179–193.doi:10.1023/A:1026154720402. . Crossref, ISIGoogle Scholar
    • Swenson S& Wahr J . 2003 Monitoring changes in continental water storage with GRACE. Space Sci. Rev. 108, 345–354.doi:10.1023/A:1026135627671. . Crossref, ISIGoogle Scholar
    • Tapley B.D, et al. 1996 The joint gravity model 3. J. Geophys. Res. 101, 28 029–28 049.doi:10.1029/96JB01645. . Crossref, ISIGoogle Scholar
    • Tapley B.D, Chambers D.P, Bettadpur S& Ries J.C . 2003 Large scale ocean circulation from the GRACE GGM01 Geoid. Geophys. Res. Lett. 30, 2163 doi:10.1029/2003GL018622. . Crossref, ISIGoogle Scholar
    • Tapley B.D, Bettadpur S, Watkins M.M& Reigber Ch . 2004 The gravity recovery and climate experiment: mission overview and early results. Geophys. Res. Lett. 31, L09607 doi:10.1029/2004GL019920. . Crossref, ISIGoogle Scholar
    • Trupin A.S, Meier M.F& Wahr J.M . 1992 Effects of polar ice on the Earth's rotation and gravitational potential. Geophys. J. Int. 113, 273–283. Crossref, ISIGoogle Scholar
    • Wahr J, Molenaar M& Bryan F . 1998 Time variability of the Earth's gravity field: hydrological and oceanic effects and their possible detection using GRACE. J. Geophys. Res. 103, 30 205–30 230.doi:10.1029/98JB02844. . Crossref, ISIGoogle Scholar
    • Wahr J, Swenson S, Zlotnicki V& Velicogna I . 2004 Time-variable gravity from GRACE: first results. Geophys. Res. Lett. 31, L11501 doi:10.1029/2004GL019779. . Crossref, ISIGoogle Scholar
    • Woodworth P.L& Gregory J.M . 2003 Benefits of GRACE and GOCE to sea level studies. Space Sci. Rev. 108, 307–317.doi:10.1023/A:1026179409924. . Crossref, ISIGoogle Scholar
    • Wu X, Heflin M.B, Ivins E.R, Argus D.F& Webb F.H . 2003 Large-scale global surface mass variations inferred from GPS measurements of load-induced deformation. Geophys. Res. Lett. 30, 1742 doi:10.1029/2003GL017546. . Crossref, ISIGoogle Scholar
    • Zumberge J, Heflin M, Jefferson D, Watkins M& Webb F . 1997 Precise point positioning for the efficient and robust analysis of GPS data from large networks. J. Geophys. Res. 102, 5005–5017.doi:10.1029/96JB03860. . Crossref, ISIGoogle Scholar