The ACCESS-AM2 climate model underestimates  aerosol concentration in the Southern Ocean;  improving aerosol representation could be problematic for the global energy balance

Fiddes, Sonya L.; Woodhouse, Matthew T.; Mallet, Marc D.; Lamprey, Liam J.; Humphries, Ruhi S.; Protat, Alain; Alexander, Simon P.; Hayashida, Hakase; Putland, Samuel; Miljevic, Branka; Schofield, Robyn

doi:10.5194/acp-25-16451-2025

Articles | Volume 25, issue 22

https://doi.org/10.5194/acp-25-16451-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-25-16451-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 25, issue 22

Research article

|

24 Nov 2025

Research article |

| 24 Nov 2025

The ACCESS-AM2 climate model underestimates aerosol concentration in the Southern Ocean; improving aerosol representation could be problematic for the global energy balance

Sonya L. Fiddes, Matthew T. Woodhouse, Marc D. Mallet, Liam J. Lamprey, Ruhi S. Humphries, Alain Protat, Simon P. Alexander, Hakase Hayashida, Samuel Putland, Branka Miljevic, and Robyn Schofield

Data sets

ACCESS-AM2 ship track data S. Fiddes https://doi.org/10.5281/zenodo.13864183

Atmospheric aerosol and Cloud Condensation Nuclei concentrations from Macquarie Island from 2016 to 2018 R. S. Humphries et al. https://doi.org/10.25919/g7jx-k629

Antarctic aerosol CN K. Hara https://doi.org/10.17592/002.2023030399

MARCUS ARM CN and CCN data reprocessed to remove ship exhaust influence R. S. Humphries https://doi.org/10.25919/ezp0-em87

Aerosol Properties, Cold Water Trial voyage (IN2015_E01): CN3 and CCN R. S. Humphries et al. https://doi.org/10.25919/ytsw-9610

RV Investigator BOM Atmospheric Data Overview (2016 onwards) A. Protat https://doi.org/10.25919/5f688fcc97166

Aerosol Properties, Ice-edge to Equator voyage (IN2016_V03): CN3 and CCN R. S. Humphries et al. https://doi.org/10.25919/g07r-b187

Polar Cell Aerosol Nucleation - atmospheric measurements from the RV Investigator voyage IN2017_V01 R. S. Humphries et al. https://doi.org/10.25919/xs0b-an24

CAPRICORN2 - Atmospheric aerosol measurements from the RV Investigator voyage IN2018_V01 R. S. Humphries et al. https://doi.org/10.25919/2h1c-t753

Observations collected between 18th October 2018 and 29th March 2019 aboard Aurora Australis by AIRBOX and associated instruments R. Schofield and R. Ryan https://doi.org/10.26179/5e546f452145d

Model code and software

sfiddes/ACCESS_aerosol_eval: ACCESS aerosol eval code published in ACP S. Fiddes https://doi.org/10.5281/zenodo.17626077

Short summary

The interaction between natural marine aerosols, clouds and radiation in the Southern Ocean is a major source of uncertainty in climate models. We evaluate the Australian climate model using aerosol observations and find it underestimates aerosol number often by over 50%. Model changes were tested to improve aerosol concentrations, but some of our changes had severe negative effects on the larger climate system, highlighting issues in aerosol-cloud interaction modelling.