Comparisons at Tide-Gauge Locations of Glacial Isostatic Adjustment Predictions with Global Positioning System Measurements

Houston, J.R. and Dean, R.G., 2012. Comparisons at tide-gauge locations of glacial isostatic adjustment predictions with global positioning system measurements. Glacial isostatic adjustment (GIA) is routinely used to adjust sea-level trends determined from tide-gauge data to improve estimates of worldwide sea-level rise. This adjustment may be appropriate for formerly glaciated high-latitude (referred to as FGHL) areas where vertical land motions due to GIA are large compared with motions produced by other phenomena. However, since GIA is only one component of vertical motion, does adjusting for it outside FGHL areas improve sea-level rise estimates or bias them? We compare global positioning system (GPS) gauge measurements with the vertical land-motion component of GIA predictions at 147 worldwide locations that are near tide gauges and outside FGHL areas and find remarkably little correlation. We analyze the data in several ways to determine the source of the lack of correlation. We also find that the average vertical motion for the 147 locations measured by GPS is subsidence, whereas the average GIA prediction is zero.