Variations in sea level are determined by three main sets of processes (changes in the density of the oceans, changes in the mass of the oceans and changes in the shape of the ocean floor and land surface), the sum of which is referred to as the ‘sea level budget’. Determining the sources and sinks of, and ultimately ‘closing’, the sea level budget is essential for understanding the drivers of past variations of sea level and for improving predictions of future behaviour.

Traditionally, individual aspects of the sea level budget have been tackled separately within discrete disciplines – oceanography, solid-Earth geophysics, glaciology, hydrology – using different data, techniques and physical understanding. The consequence has been contradictory and inconsistent results that do not always provide a good match with the observed sea level record and ‘actual’ sea level change.

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