IP1: Improved Tidal Dynamics and Uncertainty Estimation for Satellite Gravimetry (TIDUS)

PIs: Maik Thomas (FUB), Denise Dettmering (DGFI-TUM)

Research Objectives

  1. Quantify current ocean tide (OT) model uncertainties & impact on satellite gravimetry products
  2. Assess realistic errors for relevant OT constituents in different geographical regions
  3. Determine secondary ocean tide effects due to (i) minor tides, (ii) atmospheric tides, (iii) tidal loading
  4. Develop methods for achieving regional improvements of OT in critical regions

 

Innovations

  • Statistical, region-dependent error assessment of OT
  • Detailed investigation of secondary tide effects and tidal loading

Selected Results

In the first phase of the project, we focused on improving ocean tide modelling and deriving realistic error information for ocean tide models. IP1 provided uncertainty estimates, i.e., error covariance matrices, of present-day ocean tide models to the RU, in particular as input for IP2, IP4 and IP5. 

Moreover, the project focused on numerical developments of the Tidal Model forced by Ephemerides (TiME) shallow water code by introducing (i) rotated grids that avoid a singularity in the Arctic Ocean, (ii) an explicit incorporation of the dynamic feedback from self-attraction and loading, (iii) the implementation of topographic wave drag as a new energy dissipation mechanism, and (iv) the objective derivation of global model bathymetries from high-resolution ocean depth charts. The sum of all those improvements reduced the open-ocean rms of the simulated M2 tide from more than 12 cm to 3.4 cm relative to the data constrained tidal atlas FES14. Figure 1 shows the model improvement as quantified by M2 rms patterns before (a) and after (b) the model upgrades implemented in phase 1. Entailed by the substantial rms reduction and the now truly-global TiME model domain (including the entire Arctic Ocean and Antarctic ice-shelf cavities) the obtained tidal atlas serves as a valuable constraint for satellite gravimetry.

Furthermore, IP1 compiled a validation dataset of tidal constants (TICON) derived from global distributed tide gauge stations. Recently, TICON has been extended to additionally allow for the assessment of ocean tides induced by the 3rd degree of the spherical harmonics expansion of the tidal potential. The newly derived tidal constants were used to tune numerical simulations with TiME for those rarely simulated constituents. Ocean tide signatures predicted with TiME were subsequently compared with time series from super-conducting gravimeters. Another emphasis was put on the investigation of opportunities to estimate minor tides in selected coastal regions instead of inferring them by admittance theory.