A recent study by MIT indicates that a slowdown in the ocean’s circulation could lead to an increase in atmospheric carbon dioxide (CO2) levels.
This discovery challenges long-held beliefs about the ocean’s role in carbon storage and underscores the need for immediate action to mitigate climate change.
Study Findings
As climate change progresses, the ocean’s overturning circulation is expected to weaken significantly. Traditionally, scientists believed that a slower circulation would reduce the amount of carbon dioxide the ocean absorbs from the atmosphere. However, they also thought it would decrease the amount of carbon dredged up from the deep ocean, maintaining the ocean’s overall role in carbon sequestration.
Jonathan Lauderdale, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, led the study which found that weaker ocean circulation could release more carbon from the deep ocean into the atmosphere. This is due to a previously uncharacterized feedback loop involving iron, microorganisms, and ligands.
Lauderdale explained, “By isolating the impact of this feedback, we see a fundamentally different relationship between ocean circulation and atmospheric carbon levels, with implications for the climate. What we thought is going on in the ocean is completely overturned.”
Lauderdale emphasized that the ocean’s ability to store carbon might not be as reliable as previously thought, especially under the changing conditions brought about by climate change. “We can’t count on the ocean to store carbon in the deep ocean in response to future changes in circulation. We must be proactive in cutting emissions now, rather than relying on these natural processes to buy us time to mitigate climate change,” he added.
The Role of Iron and Ligands
Lauderdale’s research builds on a 2020 study that explored the interactions between ocean nutrients, marine organisms, and iron, and their influence on phytoplankton growth. Phytoplankton, microscopic plant-like organisms that live on the ocean surface, play a crucial role in absorbing carbon dioxide from the atmosphere through photosynthesis.
The study revealed that iron, a key nutrient for phytoplankton, only becomes usable when bound to ligands – organic molecules produced as byproducts of phytoplankton growth. This relationship creates a delicate balance that affects the ocean’s ability to sequester carbon.
The new study found that when ocean circulation slows down, fewer nutrients and less iron are brought up from the deep ocean to the surface. This reduction in nutrients leads to decreased phytoplankton growth, which in turn results in fewer ligands being produced. Ligands are crucial because they keep iron in a form that phytoplankton can consume. Without sufficient ligands, the iron remains insoluble and unusable by phytoplankton.
This creates a feedback loop where reduced phytoplankton growth leads to fewer ligands, which then leads to even less iron availability, further reducing phytoplankton populations and their ability to absorb CO2 from the atmosphere.
Lauderdale’s analysis revealed a new feedback loop: as ocean circulation weakens, fewer nutrients are brought up from the deep, leading to reduced phytoplankton growth and fewer ligands. This decrease in ligands makes less iron available for use, further reducing phytoplankton populations and their ability to absorb CO2 from the atmosphere.
Lauderdale explained, “Some climate models predict a 30 percent slowdown in the ocean circulation due to melting ice sheets, particularly around Antarctica. This huge slowdown in overturning circulation could actually be a big problem: in addition to a host of other climate issues, not only would the ocean take up less anthropogenic CO2 from the atmosphere, but that could be amplified by a net outgassing of deep ocean carbon, leading to an unanticipated increase in atmospheric CO2 and unexpected further climate warming.”
Implications for Climate Action
This study highlights the complex interactions between ocean chemistry, biology, and climate change. As scientists continue to refine their understanding of these processes, it becomes increasingly clear that urgent action is needed to address the root causes of climate change and reduce greenhouse gas emissions. Lauderdale emphasized the importance of proactive measures, stating, “We must be proactive in cutting emissions now, rather than relying on these natural processes to buy us time to mitigate climate change.”
The findings underscore the necessity of addressing climate change through immediate and concerted efforts to reduce emissions. Relying on the ocean’s natural processes to mitigate the effects of climate change is no longer a viable strategy. As the ocean’s ability to sequester carbon diminishes, the urgency for human intervention becomes paramount. The study calls for a reevaluation of current climate models and strategies, emphasizing the need for a proactive approach to emissions reduction and climate change mitigation.
Lauderdale’s research reveals that the interplay between ocean circulation, nutrient availability, and phytoplankton growth is more intricate than previously understood. This complexity must be taken into account when developing climate policies and strategies.
The potential for increased CO2 levels due to weaker ocean circulation adds another layer of urgency to the global effort to reduce greenhouse gas emissions. The study’s results serve as a stark reminder that human actions have far-reaching impacts on the Earth’s systems, and immediate steps must be taken to mitigate these effects.
In conclusion, the MIT study provides a new perspective on the relationship between ocean circulation and atmospheric CO2 levels. The research suggests that weaker ocean circulation could lead to higher CO2 levels in the atmosphere, challenging previous assumptions and highlighting the need for immediate and proactive climate action.
Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
