Refined European sea level estimations by combining altimetry, tide gauges, hydrographic and other data sets with improved regional GIA modeling and tailored regional GRACE gravity field models (RESEL-GRACE)
Final Report Abstract
The aim of the collaborative research proposal (CRP) within the EUROCORES Programme "4D Topography Evolution in Europe: Uplift, Subsidence and Sea Level Change (TOPO-EUROPE)" was to refine European sea level estimations by combining altimetry, tide gauges, ARGO float data, hydrographic and other data sets with improved regional GIA modeling and tailored regional GRACE (Gravity Recovery and Climate Experiment) gravity field models (RESEL-GRACE). GFZ had the task within the Individual Project (IP) 1 to derive regional mean and time variable gravity models directly from GRACE instrument data for dedicated European regions of interest, in particular for the Mediterranean Sea and the North Sea / Fennoscandia region. For this, alternative and furthermore regional representations of the gravity field have been developed which are able to map high resolution and geographical restricted features in comparison to the current global gravity fields of the Earth normally based on a series expansion of the harmonic potential in terms of spherical harmonics. During the project several alternative representations have been developed and tested such as the energy conservation approach or an enhanced approach based on calibrated GRACE K-band observations. Due to their localization characteristics and their feature of fast pyramidal algorithm spherical wavelets of Blackman type have been chosen for decomposing and reconstructing gravity data in various detail levels - in their entirety called multi-resolution representation (MRR). The different validation approaches applied show that the regional multi-resolution representation (MRR) of the GRACE gravity field variation which was developed within this project provides similar results when compared to the standard global spherical harmonic solutions provided by the GRACE Science Data Center at GFZ. For some test scenarios the correlations with In-situ data are even higher (e.g. when using GNSS-derived vertical deformations), but sometimes slightly smaller (comparisons with ocean bottom pressure data). The basin averaged mass change signal from GRACE compared to altimetry corrected from steric effects in the Mediterranean Sea (a key result of the overall project) shows slightly higher correlations. Further investigations on this topic are needed in the future. A corresponding project EGSIEM (European Gravity Service Initiative for Improved Emergency Management) has recently been funded for 2015-2017 by the Horizon2020 program.
Publications
- (2009): Changes in total ocean mass derived from GRACE, GPS, and ocean modeling with weekly resolution. Journal of Geophysical Research, 114, C11004
Rietbroek R, Brunnabend SE, Dahle C, Flechtner F, Kusche J, Schröter J, Timmermann R
(See online at https://doi.org/10.1029/2009JC005449) - (2011): Global surface mass from a new combination of GRACE, modelled OBP and reprocessed GPS data; Journal of Geodynamics
Rietbroek R, Fritsche M, Brunnabend SE, Daras I, Kusche J, Schröter J, Flechtner F, Dietrich R
(See online at https://dx.doi.org/10.1016/j.jog.2011.02.003) - (2011): Modeling the water resources of the Black and Mediterranean Sea river basins and their impact on regional mass changes; Journal of Geodynamics
aus der Beek T, Menzel L, Rietbroek R, Fegnolio-Marc L, Grayek S, Becker M, Kusche J, Stanev EV
(See online at https://dx.doi.org/10.1016/j.jog.2011.11.011) - (2011): Resolving sea level contributions by identifying fingerprints in time-variable gravity and altimetry; Journal of Geodynamic
Rietbroek R, Brunnabend SE, Schröter J, Kusche J
(See online at https://dx.doi.org/10.1016/j.jog.2011.06.007) - (2012): Separation of mass signals within GRACE monthly gravity field models by means of empirical orthogonal functions. - Journal of Geodynamics, 59-60, p. 124-132
Schmeer M, Schmidt M, Bosch W, Seitz F
(See online at https://doi.org/10.1016/j.jog.2012.03.001) - 2012. Water mass variation in the Mediterranean and Black Seas. Journal of Geodynamics, 59:168-182
Fenoglio-Marc, L., Rietbroek, R., Grayek, S., Becker, M., Kusche, J., and Stanev, E.
(See online at https://doi.org/10.1016/j.jog.2012.04.001)
