Ryan-Keogh Thomas J, Thomalla Sandy J, Monteiro Pedro M S, Tagliabue Alessandro
Southern Ocean Carbon-Climate Observatory, CSIR, Cape Town 7700, South Africa.
Marine and Antarctic Research for Innovation and Sustainability, University of Cape Town, Cape Town 7700, South Africa.
Science. 2023 Feb 24;379(6634):834-840. doi: 10.1126/science.abl5237. Epub 2023 Feb 23.
Southern Ocean primary productivity is principally controlled by adjustments in light and iron limitation, but the spatial and temporal determinants of iron availability, accessibility, and demand are poorly constrained, which hinders accurate long-term projections. We present a multidecadal record of phytoplankton photophysiology between 1996 and 2022 from historical in situ datasets collected by Biogeochemical Argo (BGC-Argo) floats and ship-based platforms. We find a significant multidecadal trend in irradiance-normalized nonphotochemical quenching due to increasing iron stress, with concomitant declines in regional net primary production. The observed trend of increasing iron stress results from changing Southern Ocean mixed-layer physics as well as complex biological and chemical feedback that is indicative of important ongoing changes to the Southern Ocean carbon cycle.
南大洋的初级生产力主要受光照和铁限制调节的控制，但铁的可用性、可获取性和需求的时空决定因素受到的限制较少，这阻碍了准确的长期预测。我们利用生物地球化学Argo（BGC-Argo）浮标和船基平台收集的历史原位数据集，展示了1996年至2022年期间浮游植物光生理学的多年代记录。我们发现，由于铁胁迫增加，辐照度归一化非光化学猝灭存在显著的多年代趋势，同时区域净初级生产力下降。观测到的铁胁迫增加趋势是由于南大洋混合层物理变化以及复杂的生物和化学反馈导致的，这表明南大洋碳循环正在发生重要变化。
