Reduction of the influence of pleistocene ice-sheet evolution on a global tide-gauge data set

Jan Hagedoorn, GeoForschungsZentrum, Potsdam, Germany
Prague, Nov 3, 2004

A consistent model for the calculation of the influence of pleistocene ice-sheet evolution on recent sea-level rise is presented, which consists of three components, the glacial isostatic adjustment (GIA), the variation of earth's rotation (ER) and the sea-level equation (SLE). The solution of the SLE describing the redistribution of glacial melt water in the oceans is implemented in conjunction with the spectral-finite element method of modeling GIA in the time domain. The additional contribution to sea-level caused by the ER due to the ice-water mass redistribution is determined by means of the Liouville-equation.
For the calculation of the influence of the pleistocene ice-sheet evolution on sea-level change, three different global models of the pleistocene deglaciation and four different viscosity stratifications are used.
To evaluate the prescribed models a method is developed independent from tide-gauge data using so-called sea-level indicators (SLI). This are geological samples, which gives an indication about relative sea-level change and which can be dated. The comparison of the predicted postglacial sea-level change induced by the pleistocene ice-sheet evolution with a set of globally distributed SLI is the basis to evaluate the acceptability of the underlying earth and ice models.
The PSMSL archived monthly mean values recorded by a globally distributed net of tide-gauge stations. From this data base time series are selected with at least 45 a of data and additional criteria are applied, to choose only time series minimally affected by other processes than the pleistocene ice-sheet evolution (e.g. tectonic or anthropogenic induced vertical displacements or sediment compaction).
The best-fitting models are employed to remove the influence of the pleistocene ice-sheet evolution on recent sea-level change recorded by the set of selected tide-gauge stations. The reduced global mean sea-level rise observed by this set of tide-gauge stations is 1.46 +/- 0.2 mm/a. Still the question remains, what this global mean value means and how it is interpreted in the context of ongoing discussion about recent sea-level rise.

Last edited Nov 18, 2004