The high-resolution simulation of the depth-integrated flow in the Great Barrier Reef, Australia
On the continental shelf of the Australian northeastern coastline, the Great Barrier Reef comprises over 2500 coral reefs in a strip that is about 2600 km in length and 200 km in width. Due to recent human activities, these ecosystems deteriorate at an alarming rate. Therefore, there is a strong need for accurate hydrodynamical simulations allowing to better understand and analyse the interactions between ecological processes and human impacts. Today, developing a high resolution, efficient and realistic model of the hydrodynamics of the whole Great Barrier Reef is still a difficult task in view of the complex bathymetry and topography. SLIM is used to achieve this objective in collaboration with the James Cook University.
The wind, the exchanges with the coral sea and the topography generate processes over a wide range of space and time scales, from a few metres to hundreds of kilometres and from a few seconds to several years. It is essential to simultaneously simulate all scales of motion, because small- and large-scale processes experience significant interactions.
Unstructured meshes are particularly useful for such domains. On the one hand, they are able to resolve reefs and coastlines much better than a structured mesh. On the other hand, they allow an increase of the resolution around the reefs and a decrease of it in more regular areas in order to represent eddies where they occur while keeping an affordable computational cost. For a uniform grid model to reproduce small-scale processes such as eddies and tidal jets, the computational cost is likely to be crippling.
With a depth rarely exceeding 50 metres, the Great Barrier Reef is rather shallow. Therefore, a two-dimensional, depth-integrated model is likely to provide realistic simulations of the circulation in this domain. However, the number of meshes is too high for the code to run properly on one single processor. We have thus implemented a parallel code in order to take advantage of UCL's high performance computing facilities.
Flood in the cleveland bay
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Turtle hatchlings dispersion around Wild Duck island (southern GBR)
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