A d30Si isotopic view on the climatic role of diatoms: driver or feedback?

大量的单细胞浮游植物，它们的外壳是由二氧化硅构成的，也就是硅藻，负责将大部分的碳从表层海洋运输到深海。因此，硅藻生产力的变化控制着大气中二氧化碳的含量以及深海中二氧化碳的输送和储存量。该提案的目的是研究硅藻在长时间和短时间尺度上驱动气候变化的作用，使用硅藻生产力的特征和新特征，即d30 Si。我们的目的是找出硅藻生产力的重大变化，这将提高二氧化碳从大气层到深海的下降，在过去的~ 50万年可能有助于地球从一个温室世界没有或很少冰的过渡，现代冰屋世界与目前的两极冰盖。此外，我们的目标是建立在一些初步的证据，硅藻是蓬勃发展的全球变暖，并找出硅藻生产力是否可以作为一个负反馈的人为排放的二氧化碳。随着南极洲周围的冰川退缩，融水流量增加，进入这个高产的沿海地区，有可能增加营养物质的输入，并提高水柱的稳定性，每一个都可以提高硅藻的生产力。我们将构建一个记录硅藻生产力，再次使用d30硅，在过去的500年中迅速积累的南极半岛的沉积物。通过针对过去的500年，我们的分析将捕捉最后一次冰川前进和恢复从小冰期时期（1850年结束）的全新世，并允许我们测试硅藻是否始终增加生产力的冰川退缩，并评估是否硅藻的反应，以人为本强迫冰川退缩是前所未有的在这个时间尺度上。

Large blooms of single celled phytoplankton which make their shells out of silica, the diatoms, are responsible for transporting the majority of carbon from the surface ocean to the deep ocean. Changes in the productivity of diatoms therefore control how much carbon dioxide resides in the atmosphere and how much is conveyed and stored in the deep ocean. The aim of this proposal is to investigate the role of diatoms in driving changing climate on long and short timescales using a characteristic and novel signature of diatom productivity, namely the d30Si. Our intention is to find out whether major changes in diatom productivity which would have enhanced the draw-down of carbon dioxide from the atmosphere to the deep ocean, during the last ~ 50 Myrs could have contributed to Earth's transition from a greenhouse world with no or little ice, to the modern ice house world with the current bipolar ice sheets. Further, we aim to build on some preliminary evidence that diatoms are flourishing with global warming and find out whether diatom productivity could act as a negative feedback on anthropogenic emissions of carbon dioxide. As glaciers retreat around Antarctica and the meltwater flux increases into this highly productive coastal zone, there is the potential for increased input of nutrients and also enhanced stability of the water column, each of which can lead to enhanced diatom productivity. We shall construct a record of diatom productivity, again using d30Si, over the last 500 years in rapidly accumulating sediments of the Antarctic Peninsula. By targeting the last 500 years, our analyses will capture the last glacial advance and recovery from the Little Ice Age period (ending 1850) of the Holocene and allow us to test whether diatoms consistently increase productivity as glaciers retreat, and assess whether the diatom response to the anthropogenically forced glacial retreat is unprecedented on this timescale.