Addressing the Problem of Land Motion at Tide Gauges

Estimation of global mean sea level change has become an area of interest for scientists in recent decades because of its importance as an indicator of climate change. Climate models predict varying degrees of change in global temperature and global sea level over the next 100 years. One way to check the validity of the models is to estimate sea level change over the last century and constrain the models to match these estimates. Traditionally, sea level change estimates have been calculated using long time series from tide gauges. There are some disadvantages to this approach however, since tide gauges have limited spatial coverage and make measurements relative to a land reference point that may be undergoing uplift or subsidence. Satellite altimetry has also been used in recent years to estimate sea level changes, but these measurements are subject to drift errors and must be calibrated. Mitchum (1998, 2000) has developed a method using the global network of tide gauges to calibrate altimeters that enables estimation of sea level change with a precision of 0.4 mm/yr. Errors in the estimates arise from a variety of sources, but the error of primary concern is that due to land motion at the tide gauge stations. In the present study we will investigate ways to improve the land motion estimate and thus reduce the error