Space-Geodetic Constraints on Glacial Isostatic Adjustment in Fennoscandia

Author:

Milne G. A.1,Davis J. L.2,Mitrovica Jerry X.3,Scherneck H.-G.4,Johansson J. M.4,Vermeer M.5,Koivula H.5

Affiliation:

1. Department of Geological Sciences, University of Durham, Durham DH1 3LE, UK.

2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138, USA.

3. Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada.

4. Onsala Space Observatory, Chalmers Institute of Technology, SE-439 92, Onsala, Sweden.

5. Finnish Geodetic Institute, FI-02431, Masala, Finland.

Abstract

Analysis of Global Positioning System (GPS) data demonstrates that ongoing three-dimensional crustal deformation in Fennoscandia is dominated by glacial isostatic adjustment. Our comparison of these GPS observations with numerical predictions yields an Earth model that satisfies independent geologic constraints and bounds both the average viscosity in the upper mantle (5 × 10 20 to 1 × 10 21 pascal seconds) and the elastic thickness of the lithosphere (90 to 170 kilometers). We combined GPS-derived radial motions with Fennoscandian tide gauge records to estimate a regional sea surface rise of 2.1 ± 0.3 mm/year. Furthermore, ongoing horizontal tectonic motions greater than ∼1 mm/year are ruled out on the basis of the GPS-derived three-dimensional crustal velocity field.

Publisher

American Association for the Advancement of Science (AAAS)

Subject

Multidisciplinary

Reference52 articles.

1. Ekman M., Terra Nova 8, 158 (1996);

2. . Ekman's map of “apparent land uplift” refers to land uplift relative to the time-varying ocean surface. By “ocean surface ” we mean the equipotential surface of the geopotential that in the spatial and temporal mean coincides with the sea surface commonly called the geoid. In regions of appreciable postglacial rebound uplift rates are about an order of magnitude greater than the GIA-induced geoid uplift.

3. The delayed isostatic response of Earth to the deglaciation of the Fennoscandian ice sheet provided the first evidence of viscous solid Earth deformation. N. A. Haskell [ Physics 6 256 (1935)] and F. A. Vening Meinesz [ K. Akad. Wet. 40 654 (1937)] estimated mantle viscosity using a small set of site-specific relative sea level data from Fennoscandia and they initiated an effort to constrain the radial viscosity profile of Earth that continues unabated [see (7) for a review].

4. Wolf D., J. Geophys. 61, 141 (1987).

5. Mitrovica J. X., Peltier W. R., J. Geophys. Res. 94, 13651 (1989).

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