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

单细胞浮游植物大量繁殖，它们的外壳由硅藻组成，负责将大部分碳从表层海洋输送到深海。因此，硅藻生产力的变化控制着大气中有多少二氧化碳，以及有多少二氧化碳被输送和储存在深海中。这项建议的目的是利用硅藻生产力的特征和新颖的特征，即d30Si，研究硅藻在驱动气候变化的长时间和短时间尺度上的作用。我们的目的是找出硅藻生产力的重大变化，这些变化将促进二氧化碳从大气到深海的吸收，在过去的50英里内，是否有助于地球从没有或几乎没有冰的温室世界过渡到现在有两极冰盖的现代冰屋世界。此外，我们的目标是建立在一些初步证据的基础上，这些证据表明，随着全球变暖，硅藻正在蓬勃发展，并找出硅藻的生产力是否可以作为对人为二氧化碳排放的负面反馈。随着南极洲周围的冰川消退，融水流量增加，进入这一生产力高的沿海地区，营养物质的输入可能会增加，水柱的稳定性也会增强，这两者都可能导致硅藻生产力的提高。我们将再次使用d30Si，在南极半岛快速积累的沉积物中构建一份过去500年来硅藻生产力的记录。通过以过去500年为目标，我们的分析将捕捉全新世小冰期(结束于1850年)以来的最后一次冰川推进和恢复，并使我们能够测试硅藻是否随着冰川退缩而持续提高生产力，并评估硅藻对人类强迫冰川退缩的反应是否在这个时间尺度上是前所未有的。

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.