Researchers led by the University of Exeter have found that a minuscule cooler layer at the ocean surface significantly enhances carbon absorption, with implications for global carbon budget assessments and climate predictions.
A recent study led by the University of Exeter reveals that a minute cooler layer at the ocean surface plays a significant role in carbon dioxide (CO₂) absorption, a finding that has profound implications for our understanding of climate change mitigation. The research highlights the pivotal role of the “ocean skin” — a layer less than 2 mm deep that is fractionally cooler than the water beneath it.
Scientists previously theorized and confirmed in laboratory settings that this subtle temperature difference should enhance CO₂ absorption by the ocean. However, observing this phenomenon in real-world ocean conditions had remained a challenge until now.
Employing precision measurements taken in the Atlantic, the research team confirmed that this cooler surface layer indeed enhances the ocean’s ability to absorb carbon.
The implications of this discovery are significant. The findings suggest that the Atlantic Ocean alone absorbs approximately 7% more CO₂ annually than previously estimated. When extrapolated across the world’s oceans, this uptick in carbon sequestration is comparable to the carbon captured by the annual forest growth in the Amazon rainforest.
Lead author Daniel Ford, a postdoctoral research fellow at the University of Exeter, emphasized the importance of these findings in global carbon assessments, particularly as the world approaches the COP29 climate change conference.
“Our findings provide measurements that confirm our theoretical understanding about CO₂ fluxes at the ocean surface,” he said in a news release. “With the COP29 climate change conference taking place next month, this work highlights the importance of the oceans, but it should also help us improve the global carbon assessments that are used to guide emission reductions.”
Ian Ashton, a senior lecturer of engineering at the University of Exeter, spoke to the collaborative nature of the research. He acknowledged the extensive international effort that culminated in this high-quality measurement campaign, supported by the European Space Agency (ESA).
“This work is the culmination of many years of effort from an international team of scientists,” Ashton said in the news release. “The European Space Agency’s support for science was instrumental in putting together such a high-quality measurement campaign across an entire ocean.”
Gavin Tilstone, a bio-optical oceanographer at Plymouth Marine Laboratory, added further context.
“This discovery highlights the intricacy of the ocean’s water column structure and how it can influence CO₂ draw-down from the atmosphere,” Tilstone said. “Understanding these subtle mechanisms is crucial as we continue to refine our climate models and predictions. It underscores the ocean’s vital role in regulating the planet’s carbon cycle and climate.”
The research contributes to the Global Carbon Budget assessment by incorporating this newfound understanding of temperature gradients into evaluations of air-sea CO₂ exchanges.
Published in the journal Nature Geoscience, the study is poised to reshape scientific approaches to measuring and predicting the ocean’s role in global carbon dynamics. As the world grapples with climate change, these insights underscore the critical, yet often overlooked, role our oceans play in mitigating the impacts of rising CO₂ levels.