The Glacial Isostatic Adjustment of Fennoscandia: from Celcius to BIFROST

Glenn Milne, University of Durham

February 2004

• Historical context

• BIFROST Project

• Forward model

• Viscosity inference

• Neotectonics

• Sea-level analysis

Brief Outline

Anders Celsius, 1701-1744

Ekman, Terra Nova, 3, 1991

http://www.ngdc.noaa.gov/paleo/slides/slideset/index11.htm

The Idea of Postglacial Rebound is Born

Jamieson, T.E. (1865), On the History of the Last Geological Changes in Scotland, Q. J. Geol. Soc. London, 21.

“It is worthy of remark that in Scandinavia and North America, as well as in Scotland, we have evidence of a depression of the land following close upon the presence of the great ice covering…It has occurred to me that the enormous weight of ice thrown upon the land may have had something to do with this depression…Then the melting of ice would account for the rising of the land, which seems to have followed upon the decrease of the glaciers.”

Ekman, Terra Nova, 3, 1991 (Fig. 4)

GLACIAL ISOSTATIC ADJUSTMENT

Surface Mass Redistribution

Earth Earth Response

• Relative sea level• Geopotential• Rotation vector• 3D solid surface deformation

ModelSurface load + Rotational potential

Rheological Earth model

Better understanding of GIA process

Constraints on Earth rheology

Constraints on surface mass redistribution

Baseline Inferences for Fennoscandian Rebound Sea Level and Tectonics

• Apply GPS to observe the present-day deformation field in Fennoscandia.

• Employ observations to:

(1) Infer GIA model parameters.

(2) Estimate secular height shift of geoid.

(3) Examine importance of neotectonic processes.

• Collaborating institutions: Finnish Geodetic Survey, Harvard-Smithsonian Center for Astrophysics, Onsala Space Observatory, Swedish National Land Survey, University of Durham, University of Toronto.

The BIFROST Network

Position Time Series: Vilhemina

Present-Day Deformation Field

GIA MODEL

Earth Forcing Earth Rheology

Rotational potential

Euler equations

Surface loading

Ice

Interdisciplinary approachOcean

Sea-level equation

Other?

Ice dammed lakes Sediment redistribution

Impulse response formalism Linear Maxwell rheology 1D structure

Ice history and Earth rheology are the key inputs

Mitrovica et al., Nature, 409, 2001.

( , ) ( , ) ( , )S U G 2.1 0.3mm/yr

• Determine new rates from extended time series.

• Incorporate dynamic glaciological models of Fennoscandian deglaciation.

• Employ new Earth models that include lateral Earth structure.

• Consider the isostatic significance of ice dammed lakes and sediment redistribution.

What’s Next?