In the 60ies there was a vigorous debate whether sea level was oscillations and reached above the present level in Mid Holocene time (the Fairbridge, 1961, concept) or was smoothly and continuously rising through the Holocene (the Shepard, 1993, concept). This is illustrated in Fig. 7-14-1. In 1971, I called attention to the fact that this was really not the major problem but instead that most "eustatic" curve - despite their large differences in Mid Holocene sea level positions - converged at around 7000-8000 BP (Fig. 7-14-2). This indicated that the ocean water masses were differently distributed in Mid Holocene time and hence that sea levels were not parallel on a global scale. This was the real Holocene sea level problem (Mörner, 1971a, b). It soon became obvious to me that the missing factor was "geoid changes". Both in 1973 and in 1974, I tried, in vain, to raise interest to include this is different IGCP projects. The concept of geoid changes was presented in 1976 (Mörner, 1976).

click on fig to enlarge

Fig. 7-14-1. In the 60ies, there was a vigorous debate on the character of Holocene sea level changes.

Fig. 7-14-2. Instead of diverging back in time, had the reason for the Mid Holocene differences been tectonic, the different curves converge at around 7000-8000 BP (Mörner, 1971a). This indicates that the ocean level was differently distributed between 7000 BP and today. This must primarily be understood in terms of geoid changes (Mörner, 1976).

Newman was one of the first to take up the idea. A number of papers on geoid changes with time came from his group (e.g. Newman et al., 1980). References at also made to Faure et al. (1980), Martin et al. (1985) and Nunn (1986). The INQUA Neotectonics Commission had a special working group on "Geoid deformation with time (paleogeodesy)" and the whole progress of the concept is well documented in it Bulletin (1979-1987). The IGCP-200 project was much devoted just to verify these global irregularities. At the same time, I tried to improve the documentation and interpretations (Mörner, e.g. 1980a, 1981, 1983, 1987, 1994, 1995). In Fig. 7-14-3, the position at 20 ka (blue), 10 ka (yellow) and Holocene maximum (violet) have been plotted against the present geoid position for sites scattered all over the globe. The graph reveals significant differences in total 20 ka depth, in rise 20 to 10 ka, in rise 10 to 0 ka and in Holocene maximum level. These differences canto be understood in terms of differential crustal movements. If the total rise is plotted against the present geoid departure from the rotational ellipsoid (Fig. 7-14-4), the data make sense: indicating a mean glacial eustatic lowering in the order of 120 m and a spread around this value due to geoid deformation in the order of +30-40 m (Mörner, 1983, 1995).

Fig. 7-14-3. Sea level changes from sites scattered all over the globe plotted against the present geoid position (with respect to the rotation ellipsoid) for 20 ka (blue), 10 ka (yellow) and Holocene maximum when above the present (violet). The non-uniformity indicates a strong contribution form geoid deformation (from Mörner, 1983).

Fig. 7-14-4. The 20 ka depth records in Fig. 7-14-3 plotted against the geoid position. This indicates a mean glacial eustatic lowering in the order of 120 m and a geoid deformational spread of +30-40 m.

The geoid deformation in association with ice caps was well known a century ago (Penck, 1982; Hergsell, 1887, von Drygalski, 1888; Woodward, 1889). In present days it has been addressed by several authors (e.g. Clark, 1976; Fjeldskaar & Kaneström, 1980). It seems relevant that the center of glacial isostatic uplift in Fennoscandia started to go at 12,700 radiocarbon years BP (Mörner, e.g. 1980b). As there was no glacial thinning at the center to account for this, the uplift may have been initiated by a geoid deformation. This may be associated with a general trans-polar VGP-shift at ~13,200 BP followed by a significant change in Earth's rotation which lead to a sudden northward displacement of the Gulf Steam so that a new biota invaded the coasts of NW Europe and Atlantic water penetrated all the way into the Barents Sea (Mörner, e.g. 1991). Informant: Mörner 2000

Selected references: Clark, J.A., 1976. Greenland's rapid post glacial emergence: A result of ice-water gravitational attraction. Geology, 4, 310-312. von Drygalski, E., 1888. Dei geoiddeformation des Eiszeit. Zeitschr. Gesell. Erdkunde Berlin, 22, 169-208. Fairbridge, R.W., 1961. Eustatic changes in sera level. Phys. Chem. Earth, 4, 99-185. Faure, H., Fontes, J.C., Hebrard, L., Monteillet, J. & Pirazzoli, P., 1980. Geoidal change and shore-level tilt along Holocene estuaries: Sénégal River area, West Africa. Science, 210, 421-423. Fjeldskaar, W. & Kaneström, R., 1980. Younger Dryas geoid-deformation caused by deglaciation in Fenno-scandia. In: N.-A. Mörner (Ed.), Earth Rheology, Iststasy and Eustasy, p. 569-574. John Wiley & Sons. Hergsell, H., 1887.Über die änderungen der gleichgewichtsflächen der Erde durch die bildung polarer eismassen dadurch erursachten schwankungen des meeresniveaus. Beitr. Geophys., Abh. Geogr. Sem. Univ. Strasbourg, i, 59-114. INQUA Nectectonics Comm., 1979-1987. Bull. INQUA Neotectonics Comm., Nos. 2-10. Martin, L., Flexor, J.-M., Blitzkow, D. & Suguio, K., 1985. Geoid change indications along the Brazilian coast during the last 7,000 years. Proc. 5th Int. Coarl Reef Congr., 3, 85-90. Mörner, N.-A., 1971a. The holocene eustatic sea level problem. Geol. Mijnbouw, 50, 699-702. Mörner, N.-A., 1971b. Relations betweem ocean, glacial and crustal changes. Geol. Soc. Am. Bull. 82, 787.788. Mörner, N.-A., 1976. Euastasy and geoid changes. J. Geology, 84, 123-151. Mörner, N.-A., 1980a. Eustasy and geoid changes as a function of core/mantle changes. In: N.-A. Mörner (Ed.), Earth Rheology, Iststasy and Eustasy, p. 335-554. John Wiley & Sons. Mörner, N.-A., 1980b. The Fennoscandian uplift: Geological data and their geophysical implication. In: N.-A. Mörner (Ed.), Earth Rheology, Iststasy and Eustasy, p. 251-284. John Wiley & Sons. Mörner, N.-A., 1981. Space geodesy, paleogeodesy and paleogeophysics. Ann. Géophys., 37, 69-76. Mörner, N.-A., 1983. Sea levels. In: R. Gardner & H. Scoging (eds) Mega-Geomorphology, p. 73-91. Oxford Univ. Press.' Mörner, N.-A., 1991. Earth's rotation and magnetism. Some new data and aspects. In: S. Flodmark (Ed.) New Approaches in Geomagnetism and the Earth's Rotation, p. 131138. World Sceitific. Mörner, N.-A., 1994. Internal response to orbital forcing and external cyclic sedimentary sequences. Spec. Publ. Int. Ass. Sediment., 19, 25-33. Mörner, N.-A., 1987. Models of global sea-level changes. In: M. Tooley & I. Shennan (eds) Sea-Level Changes, p. 332-355. Blackwell. Mörner, N.-A., 1995. Sea level Changes. Z. Geomorph. N.F., Suppl.Bd 102, 223-232. Shepard, F.P., 1963. Thirty-five thouaand years of sea level. In: T. Clements (Ed.), Essays in Marine Geology in Honor of K.O. Emery, p. 1-10. Univ. S. Calif. Press. Newman,, W., Marcus, L.F., Pardi, R.R., Paccione, J.A. & Tomecek, S.M., 1980. Eustasy and geoid changes: 1000-6000 radiocarbon years BP. In: N.-A. Mörner (Ed.), Earth Rheology, Iststasy and Eustasy, p. 355-567. John Wiley & Sons. Nunn, P.D., 1986. Implications om migrating geoid anomalies for the interpretation of high-level fossil coral reefs. Geol. Soc. Am. Bull., 97, 946-952. Woodward, R.S., 1889. On the form and the position of the sea level. U.S. Geol. Surv. Bull., 48, 1-88.