The study, published in Nature Climate Change, delved into the reasons behind this discrepancy in carbon uptake between observations and models. By utilizing various carbon datasets and model simulations, the research team found that the stronger winds that occurred in the Southern Ocean in the past decade played a significant role in this mismatch.
The stronger winds led to increased mixing between the ocean's surface water and the deep layers. This mixing, in turn, caused more CO2 to be absorbed into the ocean because the deep layers have lower CO2 concentrations than the surface water.
Moreover, these enhanced winds influenced the physical and biological processes that regulate the biological carbon pump in the Southern Ocean—the biological processes responsible for the removal of CO2 from the surface waters into the deep ocean. Changes in these processes further enhanced the carbon uptake.
The biological carbon pump involves the absorption of CO2 by phytoplankton through photosynthesis, the production of organic matter, and the eventual sinking of this organic matter into the deep ocean, where it can remain stored for thousands of years.
Previous research had suggested that human activities, particularly the burning of fossil fuels, were the sole drivers behind the observed CO2 uptake. However, this new study demonstrates that natural variability, such as stronger winds and their impact on the biological carbon pump, also contributed to the enhanced ocean carbon uptake.
This research highlights the importance of accurately representing natural climate variability in models to better understand and predict the future behavior of the ocean carbon sink, which is critical in mitigating climate change.
