May 25, 2026•2 min read•from Frontiers in Marine Science | New and Recent Articles

Future constraints and trends of the air-sea CO2 flux in the South-East Pacific region: a CMIP6 evaluation

Our take

The South-East Pacific (SEP) is vital to the global carbon cycle, yet its capacity to absorb anthropogenic CO2 remains uncertain due to significant variability in air-sea carbon flux. This study evaluates projections of future CO2 dynamics using six models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) under different emission scenarios. Findings indicate a potential shift in the northern SEP from a CO2 source to a sink by 2100, emphasizing the sensitivity of eastern boundary upwelling systems to climate change.

The recent article titled "Future constraints and trends of the air-sea CO2 flux in the South-East Pacific region: a CMIP6 evaluation" sheds light on a crucial yet often overlooked component of the global carbon cycle. The South-East Pacific (SEP) is not just a geographical area; it is a dynamic and complex ecosystem that significantly influences our planet's ability to absorb anthropogenic carbon dioxide (CO2). Despite its importance, the region's capacity to sequester CO2 remains fraught with uncertainty due to its inherent variability and spatial heterogeneity in air-sea carbon flux (FCO2). This variability is particularly pronounced when comparing the northern upwelling system, which is a significant CO2 source, with the southern fjord-dominated region, known for its carbon sink capabilities. Such contrasting dynamics are essential to understand, especially in the context of ongoing climate change and its implications for global carbon budgets.

The study employs advanced models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to evaluate how future emissions scenarios could reshape the carbon dynamics in the SEP. Under the high-emission scenario (SSP5-8.5), projections indicate a significant shift in the northern SEP, transitioning from a CO2 source to a sink by 2100. Meanwhile, the southern region is expected to strengthen its role as a CO2 sink but with increased variability. This information is critical for researchers and policymakers alike, as it underscores the sensitivity of eastern boundary upwelling systems to climate change. The findings echo themes presented in related articles, such as Multiscale oceanic response to Typhoon Noru (2022) in the South China Sea: modulation by submesoscale processes and Propagation characteristics of underwater noise from operational offshore wind farms and assessment of potential auditory interference risk to fish, both of which highlight the intricate interactions within marine ecosystems and their responses to various stressors.

The implications of these findings extend beyond regional assessments; they resonate at a global scale. The projected changes in FCO2 not only inform us about the SEP's role in carbon sequestration but also prompt critical questions about the effectiveness of current climate mitigation efforts. The study suggests that moderate climate mitigation could preserve the region's carbon dynamics, which could be pivotal for global strategies aimed at addressing climate change. This raises an essential consideration: how can we ensure that our collective actions align with preserving such vital ecosystems? As the article emphasizes, the mechanisms driving changes in CO2 seasonality are complex and warrant further investigation, particularly in light of the urgent need for climate resilience.

In conclusion, as we move forward, the sensitivity of the SEP to climate change should galvanize a concerted effort in ocean stewardship. The findings not only enhance our understanding of local carbon dynamics but also highlight the interconnectedness of marine ecosystems globally. Future research must continue to refine these projections, focusing on the underlying processes that govern air-sea CO2 fluxes. The questions remain: What specific actions can we take to mitigate these changes effectively? And how do we foster greater international collaboration to safeguard the ocean's health amidst the challenges posed by climate change? The answers will be critical as we navigate the complexities of our changing environment.

The South-East Pacific (SEP) plays a key role in the global carbon cycle. However, despite its importance, its ability to absorb anthropogenic carbon dioxide (CO2) remains poorly constrained due to strong variability and spatial heterogeneity in the air-sea carbon flux (FCO2). Uncertainties persist regarding the contrasting responses of the northern upwelling system and of the southern fjord-dominated region, as well as the mechanisms driving changes in CO2 seasonality. In the northern SEP, intense coastal upwelling off Chile makes the region a major source of CO2, while the southern SEP, characterised by Patagonian fjords and islands, acts as one of the largest coastal CO2 sinks in the Southern Hemisphere. Here, we analyse six global coupled atmosphere-ocean-carbon cycle-ecosystem models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to assess future projections of FCO2 under intermediate and high-emission scenarios (SSP2-4.5 and SSP5-8.5). We also apply a first-order Taylor decomposition of the surface ocean partial pressure of CO2 to quantify the relative contributions of its main drivers, providing a process-based interpretation of projected changes. By 2100, the SEP is projected to undergo substantial changes in carbon dynamics: under the SSP5-8.5 scenario, the multi-model mean shows that the northern SEP shifts from a CO2 source to a sink, while the southern region becomes an even stronger sink with significant increases in variability over nearly the entire region. Under SSP2-4.5, this shift in the north is partially reversed and increases in variability are milder or non-significant over a large portion of the SEP, suggesting that moderate climate mitigation could preserve the region’s carbon dynamics. Upwelling zones are projected to experience FCO2 changes faster than those in higher-latitude waters. Anthropogenic CO2 accumulation enhances background oceanic CO2 levels and DIC seasonality, while reduced temperature seasonality counteracts this amplification. These compensating mechanisms explain the projected sign reversal in the northern SEP, where DIC-driven anomalies weaken the upwelling influence and modulate future air-sea CO2 fluxes. Our results highlight the sensitivity of eastern boundary upwelling systems to climate change and suggest that moderate mitigation scenarios may partially preserve present-day carbon dynamics, with important implications for regional and global carbon budgets.

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#climate change impact#ocean data#climate monitoring#interactive ocean maps#ocean circulation#ecosystem health#air-sea CO2 flux#South-East Pacific#carbon cycle#anthropogenic CO2#FCO2#upwelling system#southern fjord-dominated region#CO2 seasonality#carbon dynamics#Patagonian fjords#Coupled Model Intercomparison Project Phase 6#coastal CO2 sinks#SSP2-4.5#SSP5-8.5