Southern Ocean CO2 uptake and buffer factor from model run 2012-2100, with links to model results

The Southern Ocean is a key region for global carbon uptake and is characterised by a strong seasonality with the annual CO2 uptake being mediated by biological carbon draw-down in summer. Here, we show that the contribution of biology to CO2 uptake will become even more important until 2100. This is the case even if biological production remains unaltered and can be explained by the decreasing buffer capacity of the ocean as its carbon content increases. The same amount of biological carbon draw-down leads to a more than twice as large reduction in CO2 (aq) concentration and hence to a larger CO2 gradient between ocean and atmosphere that drives the gas-exchange. While the winter uptake south of 44°S changes little, the summer uptake increases largely and is responsible for the annual mean response. […]

南大洋是全球碳吸收的关键区域，其显著特征为强烈的季节周期性：年度二氧化碳（CO₂）吸收量由夏季的生物碳抽取（biological carbon draw-down）过程介导。本研究表明，直至2100年，生物过程对二氧化碳吸收的贡献将愈发凸显。即便生物生产力维持不变，这一趋势依然成立，其成因可归结为：随着海洋碳含量的提升，其缓冲能力持续降低。同等规模的生物碳抽取过程，可使溶解态二氧化碳（CO₂(aq)）浓度的降幅达到原先的两倍以上，进而形成更强的海-气二氧化碳梯度，推动气体交换进程。南纬44°以南区域的冬季碳吸收量变化微弱，但夏季碳吸收量大幅提升，是年度平均碳吸收响应的主要驱动因素。[……]