Global Vertical Crustal Motion Estimates Combining Long-term Tide Gauge and Altimetry Sea-Level Records
Wan, Junkun1; Kuo, Chungyen2; Shum, C. K.1; Braun, Alexander3; Huang, Zhenwei1; Lee, Hyongki4; Tseng, Kuo-Hsin1; Yi, Yuchan1
1Ohio State University, UNITED STATES; 2National Cheng Kung University, TAIWAN; 3Univ. Texas at Dallas, UNITED STATES; 4University of Houston, UNITED STATES

To separate vertical land motion and observed sea-level rise at coastal and inland tide gauges remains to be the critical problem for the quantification rate of global sea-level rise. The techniques for the estimation of global vertical ground motion include three components: (1) glacial isostatic adjustment (GIA) forward modeling for vertical land motion prediction with the assumption that the only contributing mechanism considered is the GIA process primarily due the Last Pleistocene deglaciation; (2) direct observations from space geodetic measurements such as GPS or DORIS stations have robust survey ties to stable benchmarks of tide gauges, e.g., the approach by the GPS@Tide Gauge (TIGA) project; and (3) the method to combine altimetry and tide gauge sea level records to estimate vertical motion pioneered by Kuo et al. [2004]. Previous studies [Douglas 2001, Nerem and Mitchum. 2002, Kuo et al. 2004, 2008; Snay et al. 2007, Woppelmann et al. 2007, 2011; Ray et al. 2010; Ostanciaux et al. 2012] have used different methods and arrived at substantially different results for global vertical ground motion. An innovative approach to combine decadal radar altimeter and long-term tide gauge records based on Gauss-Markov adjustment model with stochastic constraint [Kuo et al. 2004, 2008] has demonstrated uncertainties <0.5 mm/yr for semi-enclosed or enclosed basins (Baltic Sea and Great Lakes). Here we will extend the method to open ocean regions with the objective to estimate vertical motion at global tide gauge sites. We will use long-term sea-level records from tide gauges and over 2 decades of multi-mission satellite radar altimeter data including TOPEX/POSEIDON, ERS-1/2, JASON-1/2, Envisat, GFO, Cryosat-2, and if needed with improved retracked data over coastal regions or ice-covered coastal regions. Model data or reconstructed sea-level data records will also be used. The algorithm will be applied to various coastal regions in the world, including the Bangladesh and Yangtze River Deltas, as well as regions with rapid ice loss. Our algorithm is also intended to accommodate the potentially non-linear behavior of vertical land motion caused by the elastic response to accelerated ice loss or co- or post-seismic deformation. Finally, we will assess the effect of the vertical motion estimates on the determination of the rate of global sea-level rise.