Organic carbon sequestration in Antarctic coastal polynyas

What is it about?

A study finds that Antarctic coastal polynyas, or small open-water areas within sea ice, are significant carbon sinks, effectively sequestering organic carbon, with their sequestration capacity increasing under global warming. The Southern Ocean is a significant sink of atmospheric CO2, although the contributions and mechanisms of polynyas to this carbon sink are not well understood. Chengzhen Zhou and colleagues analyzed sediment cores, covering a period between around 12,000 years ago to the present day, from beneath Antarctic polynyas to quantify organic carbon sequestration rates. Although coastal polynyas cover only 3% of the Southern Ocean the authors found, they account for around 42% of the organic carbon accumulation across the Southern Ocean. Since the Holocene, the organic carbon accumulation due to polynyas has increased nine-fold, the results show, with marine primary production as the main driver of organic carbon accumulation. As warming increases the open water areas in polynyas, the authors write, the organic carbon pump is enhanced. Further, melt of sea ice releases particulate matter that contributes to marine productivity. According to the authors, the results show that Antarctic polynyas may provide a significant negative feedback to climate change, as warming enhances their ability to sequester organic carbon.

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Photo by Dylan Shaw on Unsplash

Photo by Dylan Shaw on Unsplash

Why is it important?

Almost all climate models to date have overlooked this important carbon sink process in polynyas. This research quantifies its historical role and enhancement mechanisms, providing critical data and theoretical support for the next generation of Earth System Models to more accurately simulate and predict the Southern Ocean carbon cycle and its climate feedback."

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