Antarctic Carbon Release Surprises Scientists with New Findings

A team of scientists has discovered that the Southern Ocean emits significantly more carbon dioxide during the Antarctic winter than previously estimated. According to a study published in Science Advances on November 5, the wintertime release of CO2 has been underestimated by as much as 40%.

This research was spearheaded by scientists from the Second Institute of Oceanography and the Nanjing Institute of Geography and Limnology, both part of the Chinese Academy of Sciences. The Southern Ocean plays a crucial role in regulating the global carbon cycle, absorbing a considerable amount of carbon produced by human activities.

However, it has been described as the largest source of uncertainty in global CO2 flux calculations due to a lack of winter observations. During the dark winter months, extreme weather makes direct measurements nearly impossible, leaving the region an observational black box.

Traditional satellites, which rely on reflected sunlight for data collection, cannot operate in these conditions. To address this challenge, researchers utilized an advanced laser-based satellite instrument called LIDAR from the CALIPSO mission, combined with machine learning analysis.

This technology allowed them to observe the ocean even in total darkness, creating the first continuous record of winter CO2 exchange in the Southern Ocean. Their findings revealed that previous estimates had overlooked nearly 40% of the Southern Ocean's winter CO2 emissions.

Professor Kun Shi of the Nanjing Institute noted that these results imply a more complex and dynamic role for the Southern Ocean in the global carbon cycle than previously thought. The study also introduces a new three-loop framework to explain CO2 exchange variations across different regions of the Southern Ocean.

In the Antarctic Loop, which is south of 60 degrees South, physical factors like sea ice and salinity drive CO2 exchange. In the Polar Front Loop, between 45 and 60 degrees South, the interaction between atmospheric CO2 and biological activity is more influential.

Meanwhile, in the Subpolar Loop, north of 45 degrees South, sea surface temperature is the dominant factor. Filling this long-standing data gap is vital for creating more accurate global carbon budgets, which are foundational for climate projections used by organizations such as the Intergovernmental Panel on Climate Change.

This research highlights the potential of combining active satellite sensing with machine learning to advance our understanding of the Earth's climate system throughout the year.