The Southern Ocean's Iron Cycle through the Cenozoic

铁限制了现代南大洋的初级生产力。这反过来又减少了高纬度海洋吸收的大气二氧化碳量。这些观察结果提出了许多有趣的和迄今尚未回答的问题，即：南大洋铁的主要来源是什么？在地质时期，这些来源的铁供应有多大的弹性或可变性？铁循环如何应对地球气候的长期变化？铁循环的变化是否影响了其他营养物质（如二氧化硅）的循环？该项目将通过多方面的方法研究沉积物的来源、沉积速率和其中铁源的量化来解决这些问题。获得的详细记录将用于研究海洋营养循环的变化如何与过去6600万年前发生的主要构造，气候和地球化学重组有关。所使用的整体框架将考虑这些主要地球系统过程的相互作用，并量化它们在塑造地球上最大的铁有限生物群落的铁输送方面的各自作用。该项目将根据国际海洋发现计划钻探的富含金属的深海粘土序列的地球化学，量化南大洋铁的主要来源及其在空间和时间上的变化。这将通过将粘土的起源与放射性限制的沉积速率和其中的铁源的明确量化的统计建模相结合来实现。由此产生的重建将被用来测试假设：热液衍生铁的意义，以高纬度海洋新生代;如何开放的构造网关重新分配深源铁内南大洋;如何供应的灰尘衍生铁改变澳大利亚成为沙漠;以及，如果有变化的铁循环与硅藻的增殖。该项目补充了作为GEOTRACES计划一部分正在进行的研究，将吸引来自STEM代表性不足的社区的K-12学生，并将支持两名早期职业研究人员。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Iron limits primary productivity in the modern Southern Ocean. This, in turn, reduces the amount of atmospheric carbon dioxide that is taken up by the high-latitude oceans. These observations raise a number of fascinating and hitherto unanswered questions, namely: what are the major sources of iron to the Southern Ocean? How resilient or variable is the supply of iron from these sources over geologic time? How has the iron cycle responded to long-term changes in Earth's climate? Have changes in the iron cycle influenced those of other nutrients, such as silica? This project will address these questions by means of a multifaceted approach examining the origin of the sediment, deposition rates, and quantification of iron sources therein. The detailed records obtained will be used to examine how changes in ocean nutrient cycles relate to the major tectonic, climatic, and biogeochemical reorganizations that have occurred over the past 66 million years ago. The holistic framework used will consider the interplay of these major Earth system processes and quantify their individual roles in shaping iron delivery to the largest iron-limited biome on Earth. This project will quantify the major sources of iron to the Southern Ocean and how they changed in space and time, based on the geochemistry of metal-rich deep-sea clay sequences drilled by the International Ocean Discovery Program. This will be achieved by combining statistical modeling of the origin of the clay with radiometrically-constrained deposition rates and explicit quantification of iron sources therein. The resultant reconstructions will be used to test hypotheses regarding: the significance of hydrothermally-derived iron to the high-latitude oceans over the Cenozoic; how the opening of tectonic gateways redistributed deeply-sourced iron within the Southern Ocean; how the supply of dust-derived iron changed as Australia became a desert; and, if there were changes in the iron cycle associated with the proliferation of diatoms. This project complements ongoing research conducted as part of the GEOTRACES program, will engage K-12 students from communities underrepresented in STEM, and will support two early-career researchers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.