UoNGBR: A Regional Assimilation Barotropic Tidal Model for the Great Barrier Reef and Coral Sea Based on Satellite, Coastal and Marine Data

Abstract

All available satellite altimetry, coastal and marine data have been used to develop a new assimilative barotropic tidal model over the Great Barrier Reef (GBR) and Coral Sea using the Oregon State University Tidal Inverse Software (OTIS) with the specific consideration of bathymetry and drag coefficients. The model, named the University of Newcastle Great Barrier Reef (UoNGBR), has a 2′ × 2′ spatial resolution and includes 37 major and shallow water tidal constituents. The key to the development of UoNGBR is the use of a high-resolution bathymetry model gbr100 (3.6″ × 3.6″, corresponding to 100 meters resolution) and a recent baroclinic GBR1 hydrodynamic model. The gbr100 provides more detailed and accurate bottom topography, while the GBR1 hydrodynamic model provides spatially variable drag coefficients. These are particularly important in our study area due to the existence of numerous islands, coral reefs and complex bottom topography. The UoNGBR and seven existing tidal models have been used to detide independent datasets from the coastal tide gauges and Sentinel-3A altimeter mission. The detided datasets are then compared to the UoNGBR-detided data. The results show that UoNGBR has the minimum root sum square value (25.1 cm) when compared to those (between 26.1 and 66.7 cm) from seven other models, indicating that UoNGBR is among the best models in predicting tidal heights in the GBR and Coral Sea. Over coastline and coastal zones, the UoNGBR’s mean RMS errors are ~18 and 5 cm, respectively, smaller than TPXO models, as well as about 1–5 cm smaller than FES2012 and FES2014. These suggest that the UoNGBR model is a major improvement over other models in coastline and coastal zones.

Sea Level Rise and the Great Barrier Reef: The Future Implications on Reef Tidal Dynamics

“…The use of a constant drag coefficient across the GBR will alter the estimations of tides across the GBR. A previous study found that high‐resolution models coupled with spatially varying drag largely contribute to accurate estimates of tidal constituents across this region (Seifi et al., 2019). However, here, we found a better match to present‐day gauge data with a constant drag coefficient.…”

“…To simulate tides in coral reef environments, unstructured mesh models are the best solution as they can fulfill the need for high resolution where needed (Lambrechts, Hanert, et al., 2008; Seifi et al., 2019; Storlazzi et al., 2011). The use of empirical models, using information regarding the sea‐level change from different techniques including satellite altimetry and tidal gauges, is not sufficient to capture the complexity of tides across the GBR system (Seifi et al., 2019). Previous studies of shifts in tidal dynamics due to SLR predict moderate to large variations in the tidal cycle, due to the sensitive nature of resonant or near‐resonant tidal basins regarding changes in bathymetry (Harker et al., 2019).…”

“…This heterogeneous flow on coral reefs is due to reefs developing a complex bathymetry and topography making tidal modeling difficult (Harker et al., 2019; Seifi et al., 2019) as both high resolution and a large area need to be simulated (Burgess et al., 2007; Delandmeter et al., 2017; Storlazzi et al., 2011). To simulate tides in coral reef environments, unstructured mesh models are the best solution as they can fulfill the need for high resolution where needed (Lambrechts, Hanert, et al., 2008; Seifi et al., 2019; Storlazzi et al., 2011). The use of empirical models, using information regarding the sea‐level change from different techniques including satellite altimetry and tidal gauges, is not sufficient to capture the complexity of tides across the GBR system (Seifi et al., 2019).…”

“…Sea-level rise enhances these currents and larvae, and marine life can become immersed in the eddies and cannot escape them, this reduces their dispersal and connectivity with other populations further afield (Burgess et al, 2007;Wolanski & Spagnol, 2000). This heterogeneous flow on coral reefs is due to reefs developing a complex bathymetry and topography making tidal modeling difficult (Harker et al, 2019;Seifi et al, 2019) as both high resolution and a large area need to be simulated (Burgess et al, 2007;Delandmeter et al, 2017;Storlazzi et al, 2011). To simulate tides in coral reef environments, unstructured mesh models are the best solution as they can fulfill the need for high resolution where needed (Lambrechts, Hanert, et al, 2008;Seifi et al, 2019;Storlazzi et al, 2011).…”