Recent research shows that up to 50% of the variation in carbon uptake depth can be attributed to seafloor topography. The carbon cycle, which involves the transfer of carbon between the atmosphere, oceans, and continents, plays a critical role in controlling Earth’s climate. Several factors contribute to this cycle: volcanic eruptions and human activities release carbon dioxide into the atmosphere, while forests and oceans act as sinks and absorb this CO2. Ideally, this system balances CO2 emissions and absorption to maintain a stable climate. Carbon sequestration is one of the strategies used to strengthen this balance in the fight against climate change.

A new study has found that the shape and depth of the ocean floor explain up to 50% of the variation in the depth at which carbon accumulates in the ocean over the past 80 million years. Previously, these changes were explained by other reasons. Scientists have long known that the ocean, the largest carbon sink on Earth, directly controls the amount of carbon dioxide in the atmosphere. However, it is not yet fully understood how changes in the topography of the seabed throughout Earth history have affected the ocean’s ability to absorb carbon.

Research results and methodology

“We were able to show for the first time that the shape and depth of the ocean floor play an important role in the long-term carbon cycle,” said Matthew Bohumil, lead author of the paper and a postdoctoral researcher at UCLA Planet Earth. and space sciences.

The long-term carbon cycle has many moving parts operating on different time scales. One of these pieces is seafloor bathymetry; that is, the average depth and shape of the ocean floor. This is controlled by the relative position of the continent and oceans, sea level, and currents in the Earth’s mantle. Carbon cycle models calibrated using paleoclimate datasets form the basis for scientists’ understanding of the global marine carbon cycle and how it responds to natural perturbations.

“Generally, models of the carbon cycle throughout Earth history treat seafloor bathymetry as a constant or secondary factor,” said Tushar Mittal, co-author of the paper and professor of earth sciences at Penn State University.

A new study has been published Proceedings of the National Academy of Sciences , reconstructed the bathymetry of the last 80 million years and incorporated the data into a computer model that measured carbon absorption in the sea. The results showed that ocean alkalinity, calcite saturation state, and carbonate offset depth are highly dependent on changes in shallow parts of the ocean floor (about 600 meters or less) and how deeper sea regions (more than 1,000 meters) are distributed. These three measurements are critical to understanding how carbon is stored on the ocean floor.

Implications for climate and planetary studies

The researchers also found that in the current geological period, the Cenozoic, bathymetry alone explained 33-50% of the observed variation in carbon uptake, and concluded that by ignoring bathymetric changes, researchers were misattributing changes in carbon uptake to other less certain factors. . factors such as atmospheric CO2, water column temperature, silicates and carbonates washed into the ocean by rivers.

“Understanding important processes in the long-term carbon cycle can better inform scientists working today on marine carbon removal technologies to combat climate change,” Bohumil said. “By studying what nature has done in the past, we can learn more about the implications and feasibility of capturing the seas to mitigate climate change.”

This new understanding that the shape and depth of the ocean floor has the greatest impact on carbon uptake could also aid the search for habitable planets in our universe.

“When we look at distant planets, we currently have limited tools to tell us about their habitable potential,” said co-author Carolina Lithgow-Bertelloni, a UCLA professor and chair of the Department of Earth, Planetary and Space Sciences. “Now that we understand the important role of bathymetry in the carbon cycle, we can directly connect the evolution of a planet’s interior to its surface environment, draw conclusions from JWST observations, and infer the planet’s overall habitability.”

This breakthrough is just the beginning of the researchers’ work.

“Now that we know how important bathymetry is in general, we plan to use new simulations and models to better understand how different forms of the ocean floor will specifically affect the carbon cycle and how this has changed throughout Earth history, especially early Earth. part of it is under water,” Bohumil said.