Climate change could irreversibly modify Southern Ocean ecosystems. Marine ecosystem model (MEM) ensembles can assist policy making by projecting future changes and allowing the evaluation and assessment of alternative management approaches. However, projected changes in total consumer biomass from the Fisheries and Marine Ecosystem Model Intercomparison Project (FishMIP) global MEM ensemble highlight an uncertain future for the Southern Ocean, indicating the need for a region-specific ensemble. A large source of model uncertainty originates from the Earth system models used to force FishMIP models, particularly future changes to lower trophic level biomass and sea-ice coverage. To build confidence in regional MEMs as ecosystem-based management tools in a changing climate that can better account for uncertainty, we propose the development of a Southern Ocean Marine Ecosystem Model Ensemble (SOMEME) contributing to the FishMIP 2.0 regional model intercomparison initiative. One of the challenges hampering progress of regional MEM ensembles is achieving the balance of global standardised inputs with regional relevance. As a first step, we design a SOMEME simulation protocol, that builds on and extends the existing FishMIP framework, in stages that include: detailed skill assessment of climate forcing variables for Southern Ocean regions, extension of fishing forcing data to include whaling, and new simulations that assess ecological links to sea-ice processes in an ensemble of candidate regional MEMs. These extensions will help advance assessments of urgently needed climate change impacts on Southern Ocean ecosystems.

Key Points

Future responses of Southern Ocean primary production and animal biomass to climate change are uncertain in conservation and fishery areas

A key source of uncertainty is poorly resolved or missing sea-ice processes in climate forcings for ecological models

We propose a Southern Ocean Marine Ecosystem Model Ensemble to address key uncertainties in animal biomass response to climate change

Plain Language Summary

Climate change poses a threat to the ecosystems of the Southern Ocean and the iconic species that live there. To address this, scientists use models to estimate how these ecosystems might change in the future. Ecosystem models can help inform decisions by evaluating different strategies for managing and protecting these vulnerable marine environments. Our research focuses on improving MEM estimates by developing a group of specialized models for the Southern Ocean. This group of models, called the SOMEME, aims to reduce uncertainties by better representing regional characteristics, like sea ice, and marine life such as Antarctic krill and whales. Currently, our efforts are concentrated on making sure the group of models accurately reflects the Southern Ocean's unique conditions. This involves refining how we simulate climate effects and fishing activities, including historical whaling impacts, and examining the interactions between marine life and sea ice. By improving these models, we hope to provide clearer guidance on the potential impacts of climate change on the Southern Ocean, helping to ensure its protection for future generations.