The Creation of a Map of Current Vertical Land Movements in the UK based on an Optimal Combination of Absolute Gravity and Continuous GPS

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The proposed research aims to create a map of current vertical land movements in the UK based on an optimal combination of estimates from two geodetic surveying and monitoring techniques; the measurement of absolute gravity (AG) and the use of high precision, continuous GPS (CGPS) observations. From long term geological and geophysical studies, vertical land movements in the UK are thought to be of the order of 1 to 2 millimetres per year, with Scotland rising and the South of England subsiding, so that Great Britain is effectively 'tilting'. IESSG and NERC-POL have been working collaboratively on research related to the use of AG and CGPS for monitoring vertical land movements of this order since 1997. This past research has primarily focused on the use of AG and CGPS at tide gauges, with the aim of measuring current changes in sea level (decoupled from changes in land level) around the coast of Great Britain. For the proposed research, we will be extending our analysis from our traditional focus on tide gauges around the coast of Great Britain to consider all available CGPS stations in the UK. There are 140 such CGPS stations, which provide a density of network with station separations of about 50km, located in various geological settings throughout the UK. We will also be refining our analysis to produce new and improved estimates of vertical land movements, using the latest information, ideas and softwares available for geodetic surveying and monitoring. The proposed research is a small discrete project and will be the first attempt to create a map of current vertical land movements in the UK based on an optimal combination of AG and so many CGPS stations. With such a map it will be possible to then use model predictions of future changes in sea level in order to better assess future changes in sea level with respect to the land for all coastal regions of the UK. The proposed research could also be considered as a proof-of-concept study, as some of the 140 stations will not be suitable, due to their relatively short time series, but future refinement of the map will clearly be possible as more stations are installed and/or time series are extended in the future.