There are no speakers confirmed for future meetings. Please consider presenting, or inviting a colleague to present. Members are encouraged to reach out to @spencerwong or any co-chair if they are interested in presenting.
PhD students and early career researchers are encouraged to present. Presentations to the ESM WG can be an opportunity to receive early feedback from the community on in-progress work.
Shared Resources and Experiments:
ESM project lg87 has used 470 KSU of its 875 KSU allocation for this quarter. /g/data storage has grown to 54.3TB of the 100TB allocation.
Georgina Falster has a plan for large runs using ACCESS ESM1.5, which should be able to begin this quarter.
Do you have any proposals for shared experiments? See guidelines for how to do this. There are often used resources we can access if there are projects to use them.
CMIP7 Fast Track Presentation:
Pearse Buchanan presented results from a long spin-up simulation of a prototype ACCESS ESM1.6, focusing on the ocean biogeochemistry.
The 650 year simulation included new WOMBAT-lite ocean biogeochemistry, and the iceberg freshwater distribution scheme. Land/atmosphere changes will be incorporated in the future.
Ocean physics
Ocean temperature and salinity show small downward are downward trends which are within the range of variability. Surface temperature and salinity are quite stable, while the total volume and mass of ocean trend upwards.
The heat budget has slight positive bias, however will require further analysis. The freshwater flux is balanced appears balanced.
Ocean BGC
Carbon and alkalinity have small drifts, however with magnitudes not significant enough to cause concern.
Oxygen, alkalinity, and iron show larger drifts, and will require further investigation. Results may be impacted by a conservation bug present at the start of the run, though subsequently fixed.
Despite issues in the deeper ocean, surface iron looks good compared to observations, as do chlorophyll and CO2 fluxes.
Next steps:
Investigate cause of drift in oxygen and iron, considering changes in age, and overturning.
Incorporate parallel updates to CABLE into the spinup simulation.
2025 ACCESS-NRI Community Workshop Training Day Poll:
@jasmeen_kaur introduced the online poll for voting on training topics for the Training Day at the ACCESS-NRI Community Workshop.
The poll is available here and voting is open until the 31st of March.
Upcoming Science Presentations
Science presentations from Hannah Dawson and Wilma Huneke are scheduled for the next March 27 and April 10. . will be Shayne McGregor emphasized the importance of science presentations and encouraged contributions from both researchers and students.
Community members are encouraged to present at the working group meetings. Presentations can be on works in-progress, and students are especially encouraged to present.
Shared Resources and Experiments:
ESM project lg87 has used 535 KSU of its 875 KSU allocation for this quarter. /g/data storage remains at 54.3TB
Georgina Falster is currently running experiments with ACCESS ESM1.5, which will likely use up the remaining compute for this quarter.
Do you have any proposals for shared experiments? See guidelines for how to do this. There are often used resources we can access if there are projects to use them.
Science Presentation:
Liam Cassidy, a PhD candidate at the University of Melbourne, presented his research on temperature extremes under net zero CO2 conditions. His work focuses on understanding regional climate changes and temperature extremes after achieving net zero CO2 emissions.
The research utilized data from the Zero Emissions Commitment Model Intercomparison Project (ZECMIP), which includes idealized experiments to understand global and regional climate responses to net zero CO2 emissions. Experiments from the MIROC-ES2L, UKESM1-0-LL, and ACCESS-ESM1.5 models were compared.
The study analyzed three branching experiments based on cumulative CO2 emissions levels: 750, 1000, and 2000 petagrams, involving an initial phase of increasing CO2 emissions (1% per year) followed by an instantaneous transition to net zero emissions.
The study compared temperature and precipitation anomalies, as well as the scaling of temperature extremes, between the warming and net zero periods.
Findings:
Significant model diversity was observed in regional temperature changes after net zero emissions. Some models showed cooling over land, while others indicated continued warming, particularly in the 2000 petagram scenario. However, models were consistent in showing Southern Ocean warming after net zero.
Localized cooling was often associated with increased precipitation, while warming regions tended to experience decreased precipitation.
TXx scaling was investigated to understand whether changes in regional hydrology impact changes in temperature extremes after net-zero. TXx scaling generally decreased after net zero, though changes were heterogeneous in space with diversity between the models.
Focusing on South Africa, changes in westerly wind patterns, precipitation, and soil moisture changes were linked to changes in temperature extremes. The study highlighted the importance of understanding local feedback mechanisms, such as soil moisture and evaporative fraction, in moderating temperature extremes, as well as the value of taking a storylines approach for analysis.
These notes were partially generated by AI. If you notice any errors or omissions please feel free to modify directly, or message @spencerwong.
2025 ACCESS-NRI Community Workshop Training Day Poll:
A reminder was given about the poll for training sessions at the 2025 ACCESS-NRI Community workshop training day. Voting is now closed.
Shared Resources and Experiments:
ESM project lg87 used nearly all of its 875 KSU allocation for quarter 1. /g/data storage remains at 54.3TB
There are often opportunities at the end of the quarter to apply for spare resources from other working groups near the end of each quarter. Having experiments prepared and visible proposals on the Hive forum helps make this possible.
Proposals are now open for quarter 2. Do you have any proposals for shared experiments? See guidelines for how to do this. There are often used resources we can access if there are projects to use them.
Science Presentation:
Hannah Dawson presented on Using ACCESS CM2 to investigate the role of ocean warming in Antarctic sea ice loss.
The in-progress study aims to understand how deeper ocean warming impacts Antarctic sea ice.
Background
The past two years have seen record low winter Antarctic sea ice extents, well outside the range of historical observations. Recent work investigating the causes of this decline suggest that the ocean has played a significant contribution to this decline, which may suggest a regime shift.
Experiments
Initial condition perturbation experiments with ACCESS-CM2 were run, where warming was applied to the upwelling branch in the ocean restart files. Several warming regions were tested. The final warming area was defined based on a density, temperature, and depth constraints. Ten ensemble members were run branching from different points of the PI control simulation.
Results
Over time, subsurface heat added in the Southern Ocean spreads into the surface mixed layers.
Significant reductions in sea ice extent and volume were observed, particularly in winter and spring. The response was more pronounced in certain regions, such as East Antarctica.
The reductions in sea ice were closely aligned with regions experiencing increased
ocean temperatures, suggesting a direct link between the warming and sea ice loss.
Sea ice declines were driven by increased basal melt rather than decreased freezing rates.
Increases in sea surface temperatures and surface air temperatures were observed in the Southern Ocean. Changes were also observed in sea level pressure, however further analysis is required in interpreting the changes.
Future work
Future work will investigate into the relative roles of the applied ocean warming and atmospheric feedbacks in the sea ice decline.
Other areas for investigation will include understanding the pattern of surface freshening that occurs in the Southern Ocean.
These notes were partially generated by AI. If you notice any errors or omissions please feel free to modify directly, or message @spencerwong.
The working group meeting scheduled for 24/04 has been cancelled, as many working group members will be away between the public holidays. Working group meetings will return on 08/05.
There are no speakers confirmed for future meetings. Please consider presenting, or inviting a colleague to present. Members are encouraged to reach out to @spencerwong or any co-chair if they are interested in presenting.
Brief CMIP7 update:
New spinup simulations of ESM1.6 are currently in progress. These simulations combine ocean and land model developments from the last few months. The ESM WG meeting on 08/05 may be used to provide an update on the new spinup.
Shared Resources and Experiments:
ESM project lg87 used 411 KSU allocation for quarter 1. /g/data storage remains at 54.3TB.
@georgyfalsterâs tropical SST variability experiments have been allocated 500 KSU, and there are currently no other proposals for this quarter.
Proposals are now open for this quarter. Do you have any proposals for shared experiments? See guidelines for how to do this. There are often used resources we can access if there are projects to use them.
Working group day at the 2025 ACCESS-NRI Community Workshop:
The format of the ESM WG meeting and 2025 ACCESS-NRI Workshop was discussed. Planning is not currently advanced enough to provide concrete details. The idea of holding a joint session with another working group was raised, due to the ESM working groupâs overlap in interests with the other working groups.
Science Presentation:
Wilma Huneke presented on The ACCESS-CM2 climate model with a higher resolution ocean-sea ice component.
Background:
A new configuration of ACCESS-CM2 was set up, where the ocean and sea ice resolution was increased from 1-degree to quarter-degree. The atmosphere component was left unchanged from the existing CM2 configurations.
The ocean resolution matches the quarter degree OM2 configuration, allowing for investigation both the effects of the higher resolution, and the effects of the coupling.
Changes in bathymetry were required to prevent model crashes, and the regridding method for wind stresses was also changed from bilinear to patch to prevent an imprint of the atmospheric grid appearing in the regridded data.
Results:
A 500 year present day simulation was run with higher resolution model. Analysis focused on the final 100 years of the simulation. Comparisons were made with 1 degree CM2 present day experiment, and 0.25 and 1 degree OM2 simulations using repeat year forcings.
Sea surface temperature drifted over the whole simulation. Ocean interior temperatures drifted towards different values for each model/configuration, however the higher resolution simulations appeared to equilibrate faster.
Many biases seen in the 1 degree coupled model also appear in the 0.25 degree coupled model, including a large Southern Ocean warm bias which is larger in the higher resolution model. SST biases in eastern upwelling regions show similar patterns between the two models.
Ocean energetics as measured by sea level standard deviation were best represented in the coupled 0.25 degree model, while all analysed models generally underestimated this quantity.
All models show issues in surface mixed layer depths, with extra deep convection areas in the Wedell Sea and Ross Sea. Quarter degree OM2 significantly overestimates deep convection in the North Atlantic. The quarter degree coupled model appears to do the best job, however still shows biases.
The quarter degree coupled model shows similar biases in the ENSO pattern as the one degree model, however has an improved ENSO lifecycle, with less of a biennial cycle.
The quarter degree coupled model also displace a spurious North Atlantic multi-decadal variability, with simultaneous oscillations in the North Atlantic SST anomaly and overturning, related to the interplay between fresh water anomalies and AMOC strength. This was not present in the one degree model, however has appeared in other coupled models.
Future work:
Future work could include further increasing the ocean resolution or increasing the ocean vertical resolution.
Science Presentations: No upcoming presentations scheduled. Members encouraged contact the ESM WG co-chairs or @spencerwong to propose a topic.
LG87 Resource Usage:
836 of 875 KSUs used this quarter.
Storage usage at 55.2 TB of 100 TB allocation.
2. 2025 ACCESS Community Workshop â Working Group Day and ESM WG organisation
Scheduled for Friday, 12 September 2025.
Currently unclear who is responsible for organising the ESM WG meeting at the Community Workshop. ACCESS-NRI will provide rooms and catering; content planning is up to the group. @jemmajeffree to follow up with @dkhutch on how last yearâs meeting was planned, however additional people are needed to lead the planning.
The format for last yearâs workshop, with a single track session of presentations, was seen as successful and a model to follow for this year.
Lack of clear message that the ESM WG day is for anyone involved in coupled system research rather than just technical model development.
Discussion on organisation of ESM WG, noting that doesnât have the same level of organisation or engagement as COSIMA despite overlapping with a wide range of interests. Noted that it would be helpful to advertise the group more widely with a clearer message of who it is for.
4. NetCDF Conversion and Output Format Updates
Presented by Martin Dix
Proposed changes to atmospheric model output:
Move from stash code-based names to CMIP-style short names (e.g., ts for surface temperature).
Shift to single-variable files for better integration with intake catalogs and diagnostics.
Discussion Points:
Pros: Improved usability, consistency with ocean model outputs, easier data access.
Concerns: Increased number of files, naming inconsistencies for variables without standard names.
Suggestions:
Group related variables (e.g., carbon pools, radiation variables).
Maintain user-friendliness and performance balance.
Post detailed proposal on Hive for community feedback.
5. Science Presentation
Presenter: Dietmar Dommenget Title:How to Train Your Dragon â Tuning for Coupled Model Development with the MPI ICON-XPP Model
Introduction:
Tuning is the process of finding model parameters which optimise the behaviour of the model. Tuning is often complicated, and it can be challenging to achieve the desired model improvements.
This work focuses on tuning the MPI ICON-XPP model to optimise itâs ENSO in an atmosphere-only configuration, aiming to show that a more systematic approach to tuning can work in a simplified setup. Methodology:
A metric based on the Planton metric is used to evaluate the ENSO performance, incorporating information on climatology and processes.
30 year simulations were run while varying individual parameters, producing an estimate of error sensitivity to changes in each parameter. Sensitivities for some pairs of parameters were highly correlated.
Sensitivities calculated from the low resolution model were found to also extend to the higher resolution model.
The ENSO metric for different parameter combinations is estimated as a linear superposition of the individual parameter sensitivities.
Results
Optimising 21 parameters using the estimated ENSO metric substantially reduces the biases, and additionally reduces biases in the higher resolution model. Biases are still correlated with the original unoptimised parameters.
Applying the AMIP optimised parameters to the coupled model however was unsuccessful.
Outlook
Tuning in a systematic way can improve the model without increasing resolution.
With more resources and better optimisation schemes, better outcomes may be achievable.
Applying this form of tuning to a coupled model risks making model components artificially dependent.
Recording to be uploaded shortly.
NOTE: These minutes were partially generated using AI. Please feel free to correct any mistakes directly, or message @spencerwong with corrections.
