Abstract
Understanding the effects of climatic variability on sediment dynamics is hindered by limited ability of current models to simulate long-term evolution of sediment transfer from source to sink and associated morphological changes. We present a new approach based on a reduced-complexity model which computes over geological time: sediment transport from landmasses to coasts, reworking of marine sediments by longshore currents, and development of coral reef systems. Our framework links together the main sedimentary processes driving mixed siliciclastic-carbonate system dynamics. It offers a methodology for objective and quantitative sediment fate estimations over regional and millennial time-scales. A simulation of the Holocene evolution of the Great Barrier Reef shows: (1) how high sediment loads from catchments erosion prevented coral growth during the early transgression phase and favoured sediment gravity-flows in the deepest parts of the northern region basin floor (prior to 8 ka before present (BP)); (2) how the fine balance between climate, sea-level, and margin physiography enabled coral reefs to thrive under limited shelf sedimentation rates after ~6 ka BP; and, (3) how since 3 ka BP, with the decrease of accommodation space, reduced of vertical growth led to the lateral extension of reefs consistent with available observational data.
Highlights
Most climate projections suggest that by 2100 sea level will have risen by 0.5–1.0 m1
Our model is based on a hybrid of simplified governing equations for fluid motion and sediment transport which combines sediment dynamics induced by rivers and waves with a fuzzy logic method to simulate reef evolution
There are 35 river catchments draining into the Great Barrier Reef (GBR), two thirds of the terrigenous sediment (19.6 Mt/a) is contributed by the Burdekin and Fitzroy River catchments alone[56]
Summary
Most climate projections suggest that by 2100 sea level will have risen by 0.5–1.0 m1. Even though the actual rate of global warming far exceeds that of any previous episodes in the past 10,000 years, large changes in global climate have occurred periodically throughout Earth’s history[3] Knowing how these past changes altered sediment transport from landmasses to coasts and how sediment accumulation influenced reef development may help us identify specific patterns and improve future predictions. In the past, modelling efforts have focused mainly on the changes in regional and global wave climate, ocean biogeochemical cycles and sediment transport rates in response to projected climate-driven variations[4,5] These complex models provide important insights on time scales of the order of 10 to 100 years, but cannot capture the cumulative effect of long-term, simulated processes (>1000 years). Second, we model the 14,000 years of post-glacial evolution of sediment accumulation along the GBR and explore landscape erosion, sedimentation patterns and reef growth to assess the effectiveness of our approach
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