Influence of glacial isostatic adjustment on tide gauge measurements of secular sea level change

Abstract

Modem tide gage records of secular sea level change are strongly contaminated by the ongoing influence of glacial isostatic adjustment. In this paper we employ an accurate high‐resolution model of the glacial isostatic adjustment process to filter this signal from time series consisting of annual mean heights observed on over 500 tide gages from which records of duration longer than 10 years are available. These records are all contained in the archive of the Permanent Service for Mean Sea Level at Bidston in the United Kingdom. Prior to removal of the isostatic adjustment contamination from these records the secular sea level change signal is seen to exhibit both rising and falling levels depending upon geographic location, with regions of falling level corresponding to those that were ice covered during the last glaciation event of the present ice age. After filtering, the geographic heterogeneity in rates is considerably reduced, so much so that a globally coherent component consisting of a rise of sea level at a rate of 2.4±0.9 mm yr−1 is revealed. This could conceivably be driven by the “greenhouse effect,” although no particular mechanism has been unambiguously identified by our analyses. We investigate the impact of a number of different variants of the analysis procedure upon the inferred global signal.