Fluid dynamics, Ocean waves, Internal waves
As the SWOT wide-swath satellite altimeter mission transitions from the Science Definition Team to the Science Team, it is an opportune time to review the progress that has been made with respect to tides, and the work remaining to be done. As with previous altimeter missions, tides present both an opportunity and a challenge for the SWOT mission. The TOPEX/Jason class of altimeters have allowed high-accuracy mapping of open-ocean barotropic tides over their coverage latitudes (66°S to 66°N), but the inter-track spacing of these missions (~150 km) has limited their ability to map smaller-scale features such as shelf tides, coastal tides, and open-ocean internal tides. Because SWOT will measure sea surface height at unprecedented horizontal resolution, SWOT offers the chance to map shelf tides, coastal tides and open-ocean internal tides in unprecedented detail. In addition, the inclination of SWOT offers the chance to improve tide estimates poleward of 66°, up to the SWOT orbit inclination of 78°. At the same time, shelf tides, coastal tides, open-ocean internal tides, and high-latitude tides must be accurately removed from SWOT data before SWOT can be used to examine non-tidal signals such as mesoscale and submesoscale eddies, the main target of the SWOT oceanography mission. Shelf tides, coastal tides, and open-ocean internal tides will be difficult to remove not only because of their small horizontal scales but also because of their inherently more challenging predictability compared with open-ocean barotropic tides. For shelf and coastal tides one aspect of this is the greater number of constituents that must be considered because of possible compound tides and overtides generated by nonlinear interactions in shallow regions. An especially great challenge will be in estuaries, where the hydrology and oceanography mission interests intersect, and where the tides can be quite nonlinear and nearly unpredictable, with nonlinearity sometimes manifested by impressive tidal bores (Dronkers, 1964; LeBlond, 1978; Godin, 1999; Jay et al., 2011; among other works on river tides and their changes).
Below, after reviewing the successes with open-ocean barotropic tides enabled by previous altimeter missions, we briefly review the progress-to-date, and work remaining, on shelf tides, coastal tides, open-ocean internal tides, and high-latitude tides as they pertain to the SWOT mission. In addition, we also discuss plans for tidal correction algorithms, the need for better bathymetry, especially in coastal regions, and the need for a coordinated effort to evaluate tidal models. Finally, the document concludes with some recommendations for SWOT-related tide model development efforts.
Arbic, Brian K.; Lyard, Florent; Ponte, Aurelien; Ray, Richard D.; Richman, James G.; Shriver, Jay F.; Zaron, Edward; and Zhao, Zhongxiang, "Tides and the SWOT mission: Transition from Science Definition Team to Science Team" (2015). Civil and Environmental Engineering Faculty Publications and Presentations. 336.