Novel ocean tide solutions for application in satellite gravimetry including minor tides

The accuracy of ocean tide models has increased drastically since the launch of Topex/Poseidon and its successors. However, in regions of imperfect altimetry coverage (e.g., polar seas and coastal areas) and for minor tides with small signal-to-noise ratios, unconstrained tidal models provide crucial estimates of tidal variability in both sea-level and ocean bottom pressure that are truly global in spatial coverage.

We will present improved results from the unconstrained hydrodynamic barotropic tidal model TiME (Weis et al., 2008) that was enhanced recently with various newly developed features including (i) a rotated grid avoiding the open sea coordinate singularity allowing for global simulations without the need of introducing open ocean boundaries or spherical caps; (ii) a revised scheme for feedbacks of self-attraction and loading on ocean dynamics; (iii) updated bathymetries that also include water column height information in cavities underneath the Antarctic ice-shelves; (iv) the ability to either simulate individual partial tides or transient tidal dynamics by means of full forcing by ephemerides including contributions of the third-order lunisolar potential (Hartmann and Wenzel, 1995). Most recently, (v) a topographic wave drag parametrization following the tensor scheme of Nycander (2005) was incorporated in order to properly represent also this energy dissipation channel in TiME.

We will concentrate on results for the principal lunar tide (M2) as well as on estimates of some minor tides that are not routinely included in modern tidal atlases. In a medium term perspective, tidal results from TiME will be considered as background information for the processing of GRACE and GRACE-FO gravity fields as currently explored within the research group NEROGRAV funded by the German Research Foundation.