Toward a digital twin of the Great Barrier Reef: impact of extreme model resolution on tidal simulations

Coral reefs are topologically complex environments with a large variation over small spatial-scales. The availability of high resolution data (metre-scale) to study these environments has increased rapidly such that many researchers are actively engaged in creating a `digital twin' of these environments to aid protection and management. However, as with any model, a digital twin will only be as useful as the data used to create it. Previous numerical modelling work on coral reefs has been carried out at a range of resolutions from 10s to 1000s of metres, but to date there has been no comprehensive study on the impact of extreme model resolution at metre-scale. Here, we simulate the Capricorn Bunker region of the GBR in a high resolution, multi-scale model using grid scales of 20,000 m to 5 m and compare that to the models with minimum grid scales of 250 m and 50 m. It is shown that the observable physical processes are best simulated at extremely high resolutions, though the intermediate resolution model performs well also. The low resolution model, whilst using a resolution comparable to a number of previous studies, does not sufficiently capture local-scale processes. Numerical models play a vital role in creating a digital twin of coastal seas as they contain the mathematical representation of the biophysical and chemical processes present but are currently at a coarser resolution than satellite and bathymetric data on which digital twins could be based. Bridging this resolution gap remains a challenge.