Global and regional marine ecosystem model climate change projections
reveal key uncertainties
Abstract
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 indicates
decreasing global fish biomass with warming. However, regional
projections 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 ten 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 modelled
responses.