HEIGHT VARIATIONS AND SECULAR CHANGES IN SEA LEVEL

Abstract

The problem of understanding, assessing and quantifying the causes of sea-level changes has received increased attention during the past several years, in particular in connection with predictions regarding a rise in the global mean sea level due to global warming. The impact aspect of sea-level rise is of particular concern for many coastal areas in densely populated regions of the world. The present availability of space geodetic techniques providing high-accuracy measurements of station positions and of their time variations makes it possible to separate vertical crustal movements and absolute sea-level fluctuations. Gravimetric methods play an important role in the assessment of sea-level variations by providing completely independent measurements of vertical crustal movements. Satellite altimetry now enables the measurement of the spatial variability of sea level. Geological observations can infer former sea levels which are important to understand the present trends. This paper addresses the study of height variations and secular changes in sea level by discussing the most interesting questions and issues, by presenting the current understanding of the phenomena involved, and finally by illustrating the measuring and modeling techniques to be adopted for a comprehensive approach to the problem.