Topic: Climate
A new study finds that reducing carbon emissions may cause the Southern Ocean to release more CO2 into the atmosphere. The research was published in Science Advances and suggests that this could happen even if global temperatures are limited to 1.5°C above preindustrial levels.
Plans to limit global temperature rise depend on reaching net-zero emissions and removing carbon dioxide (CO2) from the air. This helps prevent extreme weather, sea level rise, and ecosystem loss. However, a new study published in Science Advances suggests that reducing CO2 levels may have an unexpected effect.
The Southern Ocean around Antarctica is estimated to absorb about 40-50% of human-caused carbon dioxide emissions. It does this by dissolving CO2 into colder water, which is then mixed and transported into deeper waters. Phytoplankton in sunlit surface waters also help the process by taking up CO2 for photosynthesis.
But scientists are unsure if the Southern Ocean will remain a reliable carbon sink once emissions decline. Climate models generally project continued Southern Ocean carbon uptake as emissions keep rising, but some studies suggest it could switch from absorbing CO2 to releasing it under carbon-removal pathways.
To evaluate the Southern Ocean's response to CO2 reduction scenarios, researchers ran two idealized, long-term emissions scenarios: one reaching net-zero emissions (ZEC) and one including sustained negative emissions (NEG). They compared 10 simulations for each scenario and checked the model's recent ocean CO2 uptake against observation-based estimates.
The simulations showed that the Southern Ocean changes from a modest CO2 absorber into a substantial CO2 source in both emissions scenarios. The shift persists even as atmospheric CO2 declines, indicating a delayed response rather than a quick recovery.
Why It Matters
This discovery is important for India's climate goals and efforts to reduce carbon emissions. If the Southern Ocean becomes a source of CO2, it could offset some of the benefits of reducing emissions in other areas, making it harder to achieve net-zero targets.
Key Facts
- The Southern Ocean around Antarctica absorbs about 40-50% of human-caused carbon dioxide emissions.
- Reducing CO2 levels may cause the Southern Ocean to release more CO2 into the atmosphere.
- Climate models generally project continued Southern Ocean carbon uptake as emissions keep rising, but some studies suggest it could switch from absorbing CO2 to releasing it under carbon-removal pathways.
- The simulations showed that the Southern Ocean changes from a modest CO2 absorber into a substantial CO2 source in both emissions scenarios.
- The shift persists even as atmospheric CO2 declines, indicating a delayed response rather than a quick recovery.
Key Terms
- Net-zero emissions
- When carbon dioxide emissions are balanced by the removal of an equal amount of CO2 from the atmosphere.
Implications
This discovery is important for India's climate goals and efforts to reduce carbon emissions. If the Southern Ocean becomes a source of CO2, it could offset some of the benefits of reducing emissions in other areas, making it harder to achieve net-zero targets.
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