Sea level rise and the Great Barrier Reef the future implications on reef tidal dynamics

Abstract Predicted sea-level rise (SLR) is anticipated to alter tidal dynamics in the future and this will in turn alter coastal ecosystems, flood risk, and geomorphology. Coral reefs are bathymetrically complex environments where tides play a crucial role in larval and nutrient dispersal. This complexity makes coral reef environments challenging to simulate numerically as a large area needs to be simulated but also with high resolution to capture the complexity. To investigate the influence of SLR on tidal dynamics in coral reef systems we use an unstructured mesh numerical model, with spatially varying resolution, of the Great Barrier Reef (GBR). The present-day conditions and a total of three future SLR scenarios are considered based on the RCP scenarios. The results focus on the major tidal constituents and tidal range. The M2 constituent generally decreases across gauge locations as sea-level rises but S2 generally increases. O1 and K1 display small variations or no change. The tidal range experiences ± 10% variation depending on the gauge location, meaning it is spatially varying and alters SLR by up to 10%. Overall, SLR will influence tidal dynamics across the GBR altering coastal flooding risk with a spatially varying impact. Management schemes should consider tidal range changes in addition to increases in extreme weather conditions to provide adequate preservation of the coastline, coastal cities and infrastructure in the future. Moreover, changes in tidal patterns and dynamics may alter the distributions of reef spores and larvae and should be included in future plans of reef management.