Troubled Waters: Unraveling the Uncertainty in Marine Climate Projections
A new study highlights how differences between global and regional marine ecosystem models could shape our understanding of climate change impacts.
Breaking the Ice:
Predicting the future of our oceans has never been more urgent or more complex. A recent study published in Earth’s Future reveals critical uncertainties in marine climate projections. The researchers analyzed data from an ensemble of global and regional marine ecosystem models, comparing how they predict changes in marine biomass—essentially, the total weight of all marine organisms—under different climate change scenarios.
While global models consistently project significant declines in marine biomass as the planet warms, regional models often tell a different, sometimes contradictory, story. By 2100, global models forecast widespread biomass declines, with estimates showing an average 5% drop for every 1°C of warming. However, regional models vary significantly, in some cases predicting smaller declines or even biomass increases. This discrepancy underscores the need for better alignment between model scales, as well as improved observational data to refine our predictions.
Quick Melt:
If global models overestimate marine biomass loss, they may paint an unnecessarily bleak picture for fisheries and ocean ecosystems. Conversely, if regional models underestimate these declines, policymakers and conservationists could be caught off guard, unprepared for the economic and ecological disruptions that could follow.
One major source of divergence between models lies in their resolution and scope. Global models operate at a coarse scale, averaging oceanic trends over vast spatial areas, whereas regional models zoom in on smaller ecosystems, incorporating localized factors such as nutrient upwelling, fisheries management, and species interactions. This means global models might miss some regional resilience mechanisms, while regional models may not fully capture broad-scale climate stressors.
The Thaw:
How Do Marine Ecosystem Models Function? AccumulationZone Explains.
Marine biomass projections rely on Earth system models (ESMs) that simulate future ocean conditions based on greenhouse gas emissions. These models incorporate variables such as sea surface temperature (SST), oxygen content, and primary productivity—the base of the ocean’s food chain. These factors are all changing due to climate warming.
For instance, observational data and model outputs indicate that with every 1°C rise in global temperature, marine animal biomass declines by approximately 5%. This trend is largely driven by reduced oxygen availability, increased metabolic demands, and shifts in primary production. The FishMIP (Fisheries and Marine Ecosystem Model Intercomparison Project) has shown that high-trophic-level species, such as large predatory fish, experience disproportionately severe declines due to their reliance on lower trophic levels, which are also shrinking under climate stress.
One of the major challenges in marine modeling is the scale discrepancy. Global ESMs operate on a spatial resolution of approximately 100 km² per grid cell, which smooths out fine-scale oceanographic processes such as coastal upwelling, estuarine mixing, and localized nutrient fluxes—processes that are crucial in sustaining regional fisheries. Regional models, by contrast, are designed with finer-scale forcings, often using a 10 km² resolution or higher, allowing them to capture localized ecological dynamics more effectively. However, these models frequently lack the computational power to simulate large-scale ocean trends over centuries.
The study suggests that scientists need to improve how these models interact. Better regional data should be included in global models, while global trends should inform regional studies. Long-term ocean monitoring programs—such as tracking plankton populations and fish stocks—are essential to make these models more accurate and reliable in predicting future marine ecosystem changes.
Final Thoughts
Refining our predictive tools is critical for safeguarding ocean biodiversity and the livelihoods that depend on it. Uncertainty in climate modeling is not an excuse for inaction but rather a call to deepen our understanding, improve our science, and prepare for the challenges ahead.