Sea-Level Changes Since the Early 1920's from the Long Records of Two Tidal Gauges in Shanghai, China

Abstract

This paper reports on sea-level changes at the Changjiang river mouth since the early 1920's, with a special emphasis on recent local tectonic movement, ground subsidence, and river discharge. Historical studies and mathematical correlations are used to examine the establishment and historical changes of tidal gauges and related bench markers as well as to establish the reliability of tidal records. In the past, some Chinese scientists proposed that sea-level has declined since 1950 while other foreign scientists attributed sea-level rise in the East China Sea to crustal and isostatic sinking. This study concludes that sea-level is rising at a rate about 1.0 mm a year, which is comparable to that of global sea-level rise. Meanwhile, it is found that the increase of the annual mean high tide level is remarkably greater, reflecting the estuarine morphological and hydro-dynamic effect on sea-level rise. The evidence suggests that the component of tectonic sinking accounts for only 1/3 or less of the relative sea level (RSL) rise. In contrast to the viewpoint of sea-level declining since 1950, this study shows a rising trend from 1951 to 1987, which is a continuation of sea-level rise since the beginning of this century.