An investigation of Terrestrial Reference Frames for Sea-Level Studies: Experiences from the British Isles
Abstract
The use of Global Positioning System (GPS) measurements for geodetic fixing of tide gauges and the monitoring of their apparent vertical land motions was first recommended over two decades ago. Then, the idea was to bring tide gauge benchmarks into a common and global reference, i.e. a terrestrial reference frame (TRF), that would, with an adequate long-term stability, allow the computation of accurate geocentric sea level changes, decoupled from any vertical land motions affecting the individual sea level records. This principle seemed simple, but it was soon discovered that both the accuracies achieved with GPS and the then available TRFs were not sufficient for this purpose. Today, we know that accurate vertical land motion estimates may only be obtained from GPS vertical rates from global GPS networks which have been homogeneously processed over the complete data span and properly linked into to a TRF. Furthermore, it has for the first time been demonstrated that following these rules GPS vertical rates can be used to obtain estimates of geocentric sea level changes which are superior to those using vertical rates from global glacio-isostatic adjustment models. However, it has also been recognised that some remaining uncertainty in these GPS-based estimates stem from inaccuracies in today's TRFs, which can cause the obtained GPS vertical rates to be systematically offset to those from other techniques, such as absolute gravity, or other evidence for vertical land motion from geological information (in regions where these data are available) and/or regions of coherent sea level changes. In this presentation we will describe our experiences obtained from over a decade of monitoring the vertical land motions at tide gauges in the British Isles using GPS and absolute gravity measurements. We will present our latest homogeneously reprocessed GPS and absolute gravity vertical rates and discuss the impact on regional sea level when using various reference frame implementations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.G23B0822H
- Keywords:
-
- 1222 GEODESY AND GRAVITY / Ocean monitoring with geodetic techniques;
- 1229 GEODESY AND GRAVITY / Reference systems;
- 1295 GEODESY AND GRAVITY / Integrations of techniques