Global and Regional Marine Ecosystem Models Reveal Key Uncertainties in Climate Change Projections

23 pages, 9 figures, 4 tables, supporting information https://doi.org/10.1029/2024EF005537.-- Data Availability Statement: The R scripts used to execute the analyses in the paper can be found at https://github.com/Fish-MIP/Regional_v_Global. The simulations used for the study (Eddy et al., 2023, 2024; Tittensor et al., 2023) are available at ISIMIP data repository (https://data.isimip.org/) under the tree “ISIMIP2a/OutputData/marine-fishery_regional” and “ISIMIP3a/OutputData/marine-fishery_regional,” for instructions to get access see https://www.isimip.org/gettingstarted/data-access/

Climate change is affecting ocean temperature, acidity, currents, and primary production, causing shifts in species distributions, marine ecosystems, and ultimately fisheries. Earth system models simulate climate change impacts on physical and biogeochemical properties of future oceans under varying emissions scenarios. Coupling these simulations with an ensemble of global marine ecosystem models has indicated broad decreases of fish biomass with warming. However, regional details of these impacts remain much more uncertain. Here, we employ CMIP5 and CMIP6 climate change impact projections using two Earth system models coupled with four regional and nine global marine ecosystem models in 10 ocean regions to evaluate model agreement at regional scales. We find that models developed at different scales can lead to stark differences in biomass projections. On average, global models projected greater biomass declines by the end of the 21st century than regional models. For both global and regional models, greater biomass declines were projected using CMIP6 than CMIP5 simulations. Global models projected biomass declines in 86% of CMIP5 simulations for ocean regions compared to 50% for regional models in the same ocean regions. In CMIP6 simulations, all global model simulations projected biomass declines in ocean regions by 2100, while regional models projected biomass declines in 67% of the ocean region simulations. Our analysis suggests that improved understanding of the causes of differences between global and regional marine ecosystem model climate change projections is needed, alongside observational evaluation of modeled responses

TDE, HKL, DT acknowledge funding support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). MC and JS acknowledge funding from the Spanish National Project ProOceans (RETOS-PID2020-118097RB-I00) and MC acknowledges support by the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S) to the Institute of Marine Science (ICM-CSIC). KOC acknowledges support from the One Ocean Hub and the National Research Foundation of South Africa (Grant 136481). KOC also acknowledges the resources from the Cluster for High Performance Computing–CSIR. LJS acknowledges funding and support from the EU-Horizon 2020 project “TRIATLAS” (Grant 817578) and the One Ocean Hub. [...] YJS acknowledges funding support from the Biodiversa and Belmont Forum project SOMBEE (BiodivScen ERA-Net COFUND programme, ANR contract no ANR-18-EBI4-0003-01) and the Pew Marine Fellows programme

Peer reviewed