the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Jul 2026
A high-resolution coupled atmosphere-ocean model of the Great Barrier Reef: ACCESS-EMS-GBR v1.0
Abstract. We present a new regional coupled atmosphere and ocean model of the Great Barrier Reef (GBR), Australia, called ACCESS-EMS-GBR. The model comprises a regional configuration of the Australian Community Climate and Earth System Simulator (ACCESS) atmospheric model (the United Kingdom Met Office Unified Model), coupled to the Commonwealth Scientific and Industrial Research Organisation Environmental Modelling Suite (EMS) hydrodynamic and biogeochemical model of the GBR. The model includes detailed aerosol and cloud microphysics in the atmosphere, as well as hydrodynamics, biogeochemistry, ecology and coral reef processes in the ocean. When coupled, the models form a valuable tool for simulating interactions between the atmosphere and ocean. The ACCESS-EMS-GBR model was developed to assess the plausibility and implications of marine cloud brightening (MCB) in the GBR, as part of the Reef Restoration and Adaptation Program (RRAP) Cooling and Shading Sub-program (RRAP-CS) but can also be utilised to study various processes including sources of marine aerosol and the impact of aerosol deposition on marine biogeochemistry. Here, we describe the model as configured for the GBR region, including the coupling framework, and evaluate the model skill in simulating measured aerosol and seawater temperature and irradiance. We configure the model aerosol scheme and emission sources to capture observed aerosol properties over the GBR region, with boundary layer nucleation and terrestrial biogenic emissions having a large influence on aerosol number concentration, size distribution and composition. The distribution of sea salt emissions is also expanded to include the soluble Aitken mode; a significant improvement in capability for simulating MCB and possibly for improving global climate model biases.
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Status: open (until 10 Sep 2026)
- RC1: 'Comment on egusphere-2026-2761', Anonymous Referee #1, 05 Aug 2026 reply
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Review: Jackson et al., 2026: “A high-resolution coupled atmosphere-ocean model of the Great Barrier Reef: ACCESS-EMS-GBR v1.0”
Reviewer Summary
This manuscript describes a new, regional scale coupled ocean-atmosphere model designed to study Earth system feed backs and interactions over North-Eastern Australia and the Great Barrier Reef. The main novelty of the work is coupling atmosphere and ocean climate modelling systems (ACCESS and EMS respectively) to a hydrodynamic/biogeochemical model (GBR4). This allows key atmosphere-land-ocean-climate interactions, such as the impact of riverine runoff on ocean biogeochemistry and ocean-atmosphere fluxes, to be simulated and will facilitate detailed analysis of how the Great Barrier Reef system will respond to climate change and/or climate intervention.
The manuscript also tests several new parameterizations for the UKCA model. While the author’s findings show that these parameterizations improve the model’s skill in simulating e.g. aerosol number concentrations over the North-Eastern Australia and the Great Barrier Reef region, they also suggest that the parameterizations could be usefully deployed more widely.
The manuscript is generally clear and well written. I have a few General and Technical comments and once these are addressed, I recommend that the manuscript is published.
General Comments
1. The new model configuration presented here is, by nature, complex. I think that it would be useful if the main components (and important updates like the use of CASIM) were presented in a Table or perhaps a schematic to help the reader understand the whole system.
2. Could the authors please clarify a few points regarding the revised aerosol parameterisations and their impacts on model behaviour:
Figure 4 and L473-484:
Figure 4 shows that the revised aerosol parameterizations improve the model’s simulation of Aitken mode aerosol (which is positive) but worsen the simulation of accumulation mode aerosol. If I understand correctly, the authors suggest that too many particles grow into the accumulation mode rather than ‘growing within’ the Aitken mode. Can the authors suggest how this could be addressed in GLOMAP-mode?
Have the authors tested the impact of the BLN scheme and the Aitken mode sea salt emissions independently to understand their individual impacts on the Aitken and accumulation mode aerosol (and CCN)? From the results shown, the benefit of the BLN scheme is not immediately clear to me because it appears to (1) have little impact on sulphate and organic aerosol concentrations (Figure 6) and (2) introduce a model bias by adding aerosol at particle diameters < ~20 nm that are not observed (Figure 4). While the BLN scheme improves the model’s process realism, which is an important goal, is there a scientific benefit to using the BLN in this region?
3. The new model system, as described, is specific to the North-Eastern Australia and the Great Barrier Reef region, for example bespoke emissions data sets are used. While I think this necessary to benefit from a regional scale Earth system model, could the authors add a comment on how their approach could be deployed for other locations with appropriate modifications?
Technical Comments
“Here, the SOA yield is further scaled to a factor of 0.1 (0.013) in both…”
Could the authors please clarify what the SOA is further scaled to in their configuration? If it’s 0.013, I suggest modifying the sentence to: “Here, the SOA yield is scaled further by an additional factor of 0.1 (to 0.013) in both….”
For clarity I suggest modifying “GLOMAP-mode and the cloud schemes are …..” to “Within ACCESS-EMS-GBR GLOMAP-mode and the cloud schemes are …..”
For me, there is little contrast between the line colours used for the model results making the figure less easy to interpret. Please consider using a brighter colour for the control simulation. See also Figures 4, 6 and 7.
Could the authors please clarify if the data presented in Figure 5 is from the control model simulation?
Could the author’s please increase the font sizes, particularly for the y-axis label as these are hard to read. Please also consider the font sizes for Figure 9.
I don’t think that this reference alone is suitable.