A new approach for inferring spatially continuous multi-technique vertical land motion (VLM) models for coastal areas and sea level research

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The determination of vertical land motion (VLM) along the coast contributes to a better understanding of the processes causing coastal subsidence, and the interpretation of relative sea level (RSL) rise; the latter is important for coasts sinking faster than previously predicted. We propose to create a new VLM model by integrating three datasets: VLM time series observed by Global Navigation Satellite System (GNSS) stations, VLM time series estimated from differences between radar altimetry (ALT) and tide gauge records (TG) (ALT-TG) and VLM time series derived from Interferometric Synthetic Aperture Radar (InSAR). Our model solves a problem for estimating VLM time series along the coasts that lack GNSS station coverage. We mention here that we do not intend to interpolate only the VLM rate over time, but will interpolate individual monthly VLM values along the pre-defined coastal areas of Europe and Southeast Asia. For this purpose, we will use three interpolation methods: often employed kriging approach, lately derived spatial imaging based on Delaunay triangulation, and a newly proposed triangulation approach, which can be considered as the extension of spatial imaging algorithm. Interpolation procedures will be applied to all three datasets at one time, in a one, joint interpolation procedure. The reliability of the methods will be tested for a synthetic dataset. Having created a gridded VLM time series model, we will estimate a gridded model of relative sea level (RSL) along the coasts, by computing differences between ALT and VLM (ALT-VLM). This gridded dataset will then be compared with TGs. Our project will conclude with simulation experiments that will consider whether the future addition of ultra-precise optical clocks to the geodetic infrastructure at the TG site would improve both RSL and VLM models. Against this background, this project will, through an improved integrated VLM time series model that is consistent with ALT, TG, GNSS, and InSAR datasets, better allow to constrain RSL change at monthly to decadal time scales, improve regional sea level budgets along the coasts of Europe and Southeast Asia, and thus constrain reconstructions and predictions of RSL rise.