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The mechanisms and geographic distribution of global tidal dissipation in barotropic tidal models are examined using a high resolution unstructured mesh finite element model. Mesh resolution varies between 2 and 25 km and is especially focused on inner shelves and steep bathymetric gradients. Tidal response sensitivities to bathymetric changes are examined to put into context response sensitivities to frictional processes. We confirm that the Ronne Ice Shelf dramatically affects Atlantic tides but also find that bathymetry in the Hudson Bay system is a critical control. We follow a sequential frictional parameter optimization process and use TPXO9 data‐assimilated tidal elevations as a reference solution. From simulated velocities and depths, dissipation within the global model is estimated and allows us to pinpoint dissipation at high resolution. Boundary layer dissipation is extremely focused with 1.4% of the ocean accounting for 90% of the total. Internal tide friction is much more distributed with 16.7% of the ocean accounting for 90% of the total. Often highly regional dissipation can impact basin‐scale and even ocean wide tides. Optimized boundary layer friction parameters correlate very well with the physical characteristics of the locality with high friction factors associated with energetic tidal regions, deep ocean island chains, and ice covered areas. Global complex M2 tide errors are 1.94 cm in deep waters. Total global boundary layer and internal tide dissipation are estimated, respectively, at 1.83 and 1.49 TW. This continues the trend in the literature toward attributing more dissipation to internal tides. Plain Language Summary: This study studies how and where tides dissipate energy in the ocean. Using current speeds and water levels, it is possible to estimate how much energy the ocean dissipates and find areas that are particularly energetic. An important aspect of tidal modeling is accurately setting the depth of the ocean. We identify areas of the ocean where it is very important to have accurate water depths for accurate results by using different bathymetric databases. Additionally, we find what areas of the ocean are sensitive to changes in energy dissipation. This is done via altering frictional coefficients in our model for both friction between the ocean floor and the bottom of the water column, and for internal waves that are generated near steep topography with strong vertical density gradients. With this information, we determine optimal friction coefficients, improving the tides in our model. We find that the friction coefficients obtained through the optimization process correlate well to the physical characteristics of the assigned regions. We also determine where and how energy is dissipated enabling us to pinpoint the most significant dissipation regions. Key Points: Boundary layer dissipation is concentrated in a small portion of the ocean while baroclinic conversion is more distributedBoundary layer dissipation on certain shelves controls basin‐scale tidesFrictional coefficients derived via optimization methods are consistent with regional physical and hydrodynamic characteristics [ABSTRACT FROM AUTHOR]

This paper details and tests numerical improvements to the ADvanced CIRCulation (ADCIRC) model, a widely used finite-element method shallow-water equation solver, to more accurately and efficiently model global storm tides with seamless local mesh refinement in storm landfall locations. The sensitivity to global unstructured mesh design was investigated using automatically generated triangular meshes with a global minimum element size (MinEle) that ranged from 1.5 to 6 km. We demonstrate that refining resolution based on topographic seabed gradients and employing a MinEle less than 3 km are important for the global accuracy of the simulated astronomical tide. Our recommended global mesh design (MinEle = 1.5 km) based on these results was locally refined down to two separate MinEle values (500 and 150 m) at the coastal landfall locations of two intense storms (Hurricane Katrina and Super Typhoon Haiyan) to demonstrate the model's capability for coastal storm tide simulations and to test the sensitivity to local mesh refinement. Simulated maximum storm tide elevations closely follow the lower envelope of observed high-water marks (HWMs) measured near the coast. In general, peak storm tide elevations along the open coast are decreased, and the timing of the peak occurs later with local coastal mesh refinement. However, this mesh refinement only has a significant positive impact on HWM errors in straits and inlets narrower than the MinEle and in bays and lakes separated from the ocean by these passages. Lastly, we demonstrate that the computational performance of the new numerical treatment is 1 to 2 orders of magnitude faster than studies using previous ADCIRC versions because gravity-wave-based stability constraints are removed, allowing for larger computational time steps. [ABSTRACT FROM AUTHOR]

This paper details and tests numerical improvements to ADCIRC, a widely used finite element method shallow water equation solver, to more accurately and efficiently model global storm tides with seamless local mesh refinement in storm landfall locations. The sensitivity to global unstructured mesh design was investigated using automatically generated triangular meshes with a global minimum element size (MinEle) that ranged from 1.5 km to 6 km. We demonstrate that refining resolution based on topographic seabed gradients and employing a MinEle less than 3 km is important for the global accuracy of the simulated astronomical tide. Our recommended global mesh design (MinEle = 1.5 km) based on these results was locally refined down to two separate MinEle (500 m and 150 m) at the coastal landfall locations of two intense storms (Hurricane Katrina and Super Typhon Haiyan) to demonstrate the model's capability for coastal storm tide simulations and to test the sensitivity to local mesh refinement. Simulated maximum storm tide elevations closely follow the lower envelope of observed high water marks (HWMs) measured near the coast. In general, peak storm tide elevations along the open coast are decreased and the timing of the peak occurs later with local coastal mesh refinement. However, this mesh refinement only has a significant positive impact on HWM errors in straits and inlets narrower than the MinEle, and in bays and lakes separated from the ocean by these passages. Lastly, we demonstrate that the computational performance of the new numerical treatment is one-to-two orders of magnitude faster than studies using previous ADCIRC versions because gravity-wave based stability constraints are removed allowing for larger computational time steps. [ABSTRACT FROM AUTHOR]