HEIGHT VARIATIONS AND SECULAR CHANGES IN SEA-LEVEL

The problem of understanding, assessing and quantifying the causes of sea-level changes has received increased attention during the past sev eral years, in particular in connection with predictions regarding a r ise in the global mean se:a level due to global warming. The impact as pect of sea-level rise is of particular concern for many coastal areas in densely populated regions of the world. The present availability o f space geodetic techniques providing high-accuracy measurements of st ation positions and of their time variations makes it possible to sepa rate vertical crustal movements and absolute sea-level fluctuations. G ravimetric methods play an important role in the assessment of sea-lev el variations by providing completely independent measurements of vert ical crustal movements. Satellite altimetry now enables the measuremen t 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 secul ar changes in sea level by discussing the most interesting questions a nd issues, by presenting the current understanding of the phenomena in volved, and finally by illustrating the measuring and modeling techniq ues to be adopted for a comprehensive approach to the problem. (C) 199 8 Published by Elsevier Science Ltd. All rights reserved.