Regional and global mean sea level variability over the modern instrumental period

Author: Rui M. Ponte, C. Wunsch and P. Heimbach
December 1, 2008
AGU Fall Meeting, San Francisco

Ponte, R.M., C. Wunsch, and P. Heimbach, 2008. Regional and global mean sea level variability over the modern instrumental period. AGU Fall Meeting, San Francisco, December 2008.

The possibility of sea level rise in the context of global climate change has received much attention in recent years. Determination of sea level rise and its causes, either globally or regionally, must however cope with other signals in the sea level record. A comprehensive look at sea level variability over the modern instrumental period (1992-present) is made possible by the 3-dimensional, time-dependent ocean state estimates produced under ECCO-GODAE. Such estimates involve a least-squares optimization that produces a "best" fit of the MITgcm to most available ocean data, including several altimetric missions and all in-situ hydrography. The estimated regional sea level patterns exhibit interannual and longer period variability that can easily mask expected long-term trends in mean sea level. Both steric and mass changes contribute to sea level change at regional and global levels, and thermal and haline effects are evident over the full water column, stressing the need for surface-to-bottom measurements. Spatial patterns of variability are not simply related to a passive ocean response to heating and cooling but involve changes in its 3-dimensional circulation. Uncertainties in mean sea level estimates remain large given the possibility of systematic errors in all datasets, including the atmospheric surface fluxes. Various ways of improving model formulation and implementation of data constraints relevant for determining global mean quantities are examined.