On post-glacial sea level – II. Numerical formulation and comparative results on spherically symmetric models

Authors: Kendall, Roblyn A.¹; Mitrovica, Jerry X.¹; Milne, Glenn A.²

Source: Geophysical Journal International, Volume 161, Number 3, June 2005 , pp. 679-706(28)

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Abstract:

SUMMARY

Theoretical approaches to computing gravitationally self-consistent sea-level changes in consequence of ice growth and ablation are comprised of two parts. The first is a mapping between variations in global sea level and changes in ocean height (required to define the surface load), and the second is a method for computing global sea-level change arising from an arbitrary surface loading. In Mitrovica & Milne (2003) (Paper I) we described a new, generalized mapping between sea-level change and ocean height that takes exact account of the evolution of shorelines associated with both transgression and regression cycles and time-dependent marine-based ice margins. The theory is valid for any earth model. In this paper we extend our previous work in three ways. First, we derive an efficient, iterative numerical algorithm for solving the generalized sea-level equation. Secondly, we consider a special case of the new sea-level theory involving spherically symmetric earth models. Specifically, we combine our iterative numerical formulation with viscoelastic Love number theory to derive an extended pseudo-spectral algorithm for solving the new sea-level equation. This algorithm represents an extension of earlier methods developed for the fixed-shoreline case to precisely incorporate shoreline migration processes. Finally, using this special case, we quantitatively assess errors incurred in previous efforts to extend the traditional (fixed shoreline) sea-level equation of Farrell & Clark (1976) to treat time-dependent shorelines. We find that the approximations adopted by Johnston (1993) and Milne (1998) to treat transgression and regression at shorelines introduce negligible ( sim

1 per cent) error into predictions of post-glacial relative sea-level histories. In contrast, the errors associated with the Peltier (1994) sea-level equation are an order of magnitude larger, and comparable to the error incurred using the traditional sea-level theory. Furthermore, our numerical tests verify the high accuracy of the Milne (1998) approximation for treating the influence of grounded, marine-based ice.

Keywords: glacial rebound; sea level

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-246X.2005.02553.x

Affiliations: 1: Department of Physics, University of Toronto, 60 St George Street, Toronto, Ontario, Canada M5S 1A7., Email: rkendall@physics.utoronto.ca 2: Department of Geological Sciences, University of Durham, Science Labs, South Road, Durham DH1 3LE, UK

Publication date: 2005-06-01

On post-glacial sea level – II. Numerical formulation and comparative results on spherically symmetric models

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