Coral Reef Exposure to Damaging Tropical Cyclone Waves in a Warming Climate

Tropical cyclones generate large waves that physically damage coral communities and are commonly cited as a worsening threat to coral reefs under climate change. However, beyond projections of ocean basin-scale changes in cyclone intensity, the other determinants of future coral reef damage such as cyclone size and duration remain uncertain. Here, we determine the extent to which downscaled cyclones represent observed cyclone characteristics that influence wave damage to Australian coral reef regions. We then investigate mid-century (2040-2060) and end of century (2080-2100) downscaled tracks to assess whether cyclone characteristics will change with future warming under a high-emissions scenario. We find that spatial uncertainties in downscaled cyclogenesis and track positions limit estimates of reef damage for individual coral reefs and regions. Further, the models are unable to reproduce the most reef damaging cyclones for any of the regions. The downscaled tracks capture observed cyclone characteristics, such as size, impacting the Great Barrier Reef well, but perform poorly for the Northern Territory, with mixed performance for the Coral Sea and Western Australia. We find no clear evidence that cyclones will cause more damage to Australian coral reef regions in the future, at least based on the climate models and downscaling approach examined here. There is increasing interest in using tropical cyclone projections to assess future coral reef exposure to damaging waves. We recommend caution when interpreting such projections due to large uncertainty in the mechanisms that influence reef damaging tropical cyclone characteristics and how these will change with future warming.

Automated summary

This study examines the ability of downscaled cyclones to represent observed cyclone characteristics that affect wave damage to Australian coral reef regions. The research finds spatial uncertainties in downscaled cyclogenesis and track positions limit estimates of reef damage, and the downscaled tracks perform differently for different regions. The study also suggests that there is no clear evidence that cyclones will cause more damage to Australian coral reef regions in the future.