A new scientific paper has detailed the development and validation of a high-resolution ocean model designed to better represent the complex movement of water across the central Great Barrier Reef.

Tides, winds, ocean currents and freshwater flowing from coastal catchments continually interact across the Great Barrier Reef, influencing how heat, nutrients, sediments and biological material move through the system. Understanding these processes is fundamental to effective Reef management. However, modelling them accurately and cost-effectively across such a complex environment is challenging.

New research published in Ocean Modelling describes a high-resolution Regional Ocean Modelling System (GBR ROMS) developed for the central Great Barrier Reef (GBR) with support from the Reef and Rainforest Research Centre (RRRC) and GFD Ltd.

Operating at approximately one-kilometre horizontal resolution with 25 vertical layers, the model simulates temperature, salinity, currents and water-column structure. It also incorporates scaled real-time discharge observations from 18 rivers distributed across 104 coastal grid cells, providing a detailed representation of freshwater entering the Reef lagoon in this region.

Preserving the Reef’s complex underwater landscape

One of the study’s key advances addresses a fundamental challenge in ocean modelling: representing complex underwater topography accurately, verifiably, and cost-effectively, while maintaining a stable model.

The Great Barrier Reef contains narrow reef passages, nearshore channels and steep changes in depth that can strongly influence how water moves. The researchers developed an improved linear programming approach that selectively smooths the model’s bathymetry while preserving more of these important features.

Compared with a conventional smoothing method under an equivalent constraint, the new approach required 25% less modification of the original bathymetry and altered 30% fewer grid cells. This enables the model to better retain features important to circulation and cross-shelf exchange.

Testing predictions against the real Reef

The model has now been tested against several independent sources of observations.

Tidal predictions were compared with measurements from five tide gauges between Port Douglas and Townsville, while temperature and salinity were tested against four missions by Integrated Marine Observing System’s ocean gliders near Mission Beach spanning wet and dry seasons.

The model successfully reproduced observed temperature and salinity patterns, including strong wet-season freshwater plumes and the vertical stratification they create. Comparison with 355 days of Himawari satellite observations also produced a sea-surface temperature error of just 0.38°C and a correlation of 0.98.

These results complement RRRC’s field-based testing of GBR ROMS. In early 2026, an ocean glider mission was positioned in response to the model’s prediction of a strong low-salinity front between Cardwell and Cairns. The glider subsequently detected freshwater influence tens of kilometres offshore and strong stratification through the upper water column. RRRC has also coordinated satellite-tracked ocean drifter experiments to collect observations of surface-water movement for comparison with model predictions (another paper just published in the journal Oceanography).

From ocean dynamics to Reef management

Accurately representing water movement has applications well beyond predicting currents. Ocean circulation influences where river plumes travel, how heat accumulates around reefs, and how sediments, nutrients and biological material move through the Great Barrier Reef.

GBR ROMS provides a validated foundation for investigating these processes and can already operate in near-real time, producing six-day forecasts updated daily. Future development could extend the model’s geographic coverage and incorporate wave dynamics, data assimilation and higher-resolution modelling of individual reef systems.

The publication represents an important milestone in developing GBR ROMS from an experimental modelling capability into a scientifically validated, cost-effective and open-source tool with the potential to support more responsive, targeted and evidence-based Reef management. The tool and results are already being incorporated into a National Environmental Science Program Marine and Coastal Hub project looking into connectivity and reef resilience on the GBR.

Development and validation of a high-resolution ROMS model for the Central Great Barrier Reef using LP-optimised bathymetry and realistic river forcing, by Prof Ivica Janekovic and Dennis Stanley, is published in Ocean Modelling. The research was supported by RRRC and GFD Ltd, with scientific guidance from RRRC’s Dr Suzanne Long and Dr Sheriden Morris.