Christopher Watson (University of Tasmania, Australia)

It has now been more than 20 years since geodetic measurement of vertical land movement at, or near to, tide gauges (TGs) was proposed. A large number of mainly Global Positioning System (GPS) receivers have been deployed since these recommendations were made, either to explicitly monitor TG motion or, more often, as part of larger-scale scientific and/or government-funded networks. As a result, vertical land movement is now being measured at several hundred sites “near” to tide gauges, although “near” could be tens or hundreds of kilometres. Even allowing for this, there are still a large number of TGs that are routinely used for climate studies that are not presently adequately monitored by geodetic techniques. Here, we report on a priority list of TGs where GNSS data are not available for analysis by the international community. We provide this analysis from the perspectives of two applications: (i) Long-running tide gauges contributing data for studies of long-term sea-level change; and (ii) Tide gauges used in calibration/validation of satellite altimeters.